Lava flows and thermal activity persist during February-July 2023

Heard, a remote island located in the southern Indian Ocean, consists of two volcanic structures: Big Ben and the smaller Mt. Dixon. The active Mawson Peak is located within a 5-6 km-wide caldera breached to the SW side of Big Ben. Intermittent eruptions have occurred since 1910; the current eruption period began in September 2012, which has mainly been characterized by thermal activity and intermittent lava flows (BGVN 48:02). This report covers continuing effusive and thermal activity during February through July 2023 using satellite data.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed intermittent low-to-moderate thermal activity during February through July 2023 (figure 54). There were short periods of no thermal activity during early and late June. MODIS satellite instruments using the MODVOLC thermal algorithm also detected a total of 34 strong thermal hotspots on 8 and 24 February, 5, 12, 19, 20, and 22 March, 8, 9, 15, 16, 28, and 29 April, 2 and 18 May, 2 and 3 June, and 11, 13, and 15 July. On clear weather days, infrared satellite imagery captured thermal activity to the W of the summit of Mawson Peak (figure 55). Fresh and cooling lava flows were observed on the SW flank in infrared satellite images underneath the active thermal anomalies (figures 55 and 56). This activity was captured at least 12 times in satellite imagery on 12 February, 6, 21, 24, and 31 March, 5, 13, 25, and 30 April, 23 and 25 May, and 17 July.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).

Information is preliminary and subject to change. All times are local (unless otherwise noted)

February 1985 (SEAN 10:02) Cite this Report

Lava flow from upper S flank vent; plume

During the night of 14-15 January, personnel of the French oceanographic mission Sibex (ship) observed an eruption on Heard Island. A lava flow emerged from a vent at ~ 2,750 m altitude, on the upper S flank (between Big Ben and Mawson, figure 1). For 2 days, a plume was visible from 32 km away. An image from the NOAA 7 polar orbiting satellite showed a diffuse plume extending SE from the island on 14 January at 1712. The plume was narrow over the island, widening over the ocean until obscured by weather clouds 20-25 km to the SE. The next day at 1658, NOAA 7 imagery showed that the island was free of weather clouds, but no volcanic plume was evident.

Reference. Neumann van Padang, M., 1963, Catalog of active volcanoes of the world, Part XVI.

Information Contacts: J. Bull, Terres Australes et Antarctiques Françaises; A. Giret, Expeditions Polaires Françaises; J-L. Cheminée, IPG, Paris; W. Gould, NOAA.

October 1985 (SEAN 10:10) Cite this Report

Steam and two areas of glow

No further reports of volcanic activity on this remote, uninhabited island were received until 29 September, when scientists from the MV Nella Dan (ship) observed steam rising from a vertical crack in the Gotley Glacier (on the SW flank). On 4 October at about 2100, from 11.5 km offshore, two distinct areas of glow were observed: at the summit, and at a point between 1,500 and 2,000 m altitude in Gotley Glacier, 6.5-7 km from the summit. The observers believed the flank glow to be a second source of lava, although they noted the possibility that lava originating at the summit might have flowed under the glacier and emerged at that point. Space Shuttle astronauts observed the volcano emitting vapor every day during their 30 October-5 November mission and took a photograph (no. 61A-49-047), but there was no sign of fresh lava or ash on the summit.

Further Reference. Quilty, P., 1985, New volcanic vent on Heard Island?: ANARE News, December. 1985, p. 11.

Information Contacts: R. Varne, Univ. of Tasmania; M. Helfert, NASA.

May 1992 (BGVN 17:05) Cite this Report

Plumes and glow; volcano morphology and 1986-87 activity described; 1992 summit eruption

[The following from Graeme Wheller] includes observations of continued activity in late 1986 and early 1987, and a renewed eruption in 1992.

Volcano morphology. Heard Island consists of two volcanic cones, Big Ben and Mt. Dixon, joined by a narrow isthmus (figure 2). Both cones are young, but only Big Ben has been observed to erupt. Many young lavas, including two that are unvegetated, lie on the flanks of Mt. Dixon. The separation of the two volcanoes is evident from the contrasting petrographic, geochemical, and isotopic characteristics of their respective eruptives [(Barling and others, 1994)].

Big Ben is a large, glacier-covered, composite cone 20-25 km in diameter at sea-level, consisting mainly of basaltic lavas and lesser ash and scoria. Its summit region consists of a SW-facing semi-circular ridge 5-6 km in diameter, 2,200-2,400 m asl. The ridge appears to have formed from breaching of the SW flank of Big Ben, possibly by landsliding caused by seismicity or a laterally directed blast. The E, N, and W flanks of Big Ben have been deeply scoured by glacial erosion, forming high-standing radial ribs to 7-8 km long.

Eruptions have built a new regularly shaped cone, Mawson Peak, within the breached region of the summit. Mawson Peak is snow-and ice-covered on all sides, . . . and its SW flank slopes smoothly to the coast. All . . . historical volcanism has apparently originated at the summit of Mawson Peak.

Young volcanic deposits. Mt. Dixon, much smaller than Big Ben, appears to be the latest manifestation of volcanic activity that has created a peninsula 9 km long and up to 5 km wide extending from the NW side of Big Ben. Mt. Dixon, at the end of the peninsula, is a glacier-covered rounded cone 706 m tall. More than 20 separate relatively young basaltic lava flows have been identified on its flanks, including two that are largely vegetation-free and may have been erupted within the last few hundred years. These lavas have flowed from vents on the upper flanks of Mt. Dixon, except for one from a fissure marked by an elongate scoria ridge ~1 km long near the base of the S flank. A crater ~50 m in diameter occurs at the head of one W-flank flow ~1 km inland. Several small hornitos occur on the lava flow near this crater. One is still well-formed, ~2.5 m high and 3-4 m in diameter, but the others have largely collapsed. On the W and N flanks of Mt. Dixon, particularly near Red Island, trachytic lavas lie beneath the basalt lavas.

Eleven parasitic scoria cones and associated small basaltic lava flows occur around the coastline . . . . Some are at or near the edges of vertical sea cliffs, indicating that erosion by the sea may have obliterated other cones. The parasitic cones are typically ~100 m high and well-formed with deep central craters. Lava spatter usually occurs abundantly around the upper parts of the cones. Lavas produced from these vents are typically small-volume pahoehoe flows. From their morphology and relative lack of vegetation, the cones and their lavas may be only a few thousand years old. On Azorella Peninsula, the parasitic cone forms the W side of Corinth Head which, together with Rogers Head, appears to be a remnant of an older and much larger cone formed of thinly stratified leucocratic tuff. The basaltic flow erupted from the Corinth Head crater contains partly collapsed tumuli and lava tunnels.

A similarly youthful, trachytic, airfall (Plinian?) pumice deposit 1-1.5 m thick occurs at the E end of the island. The lower 0.5 m of the deposit is distinctly darker than the upper part, showing a sharp horizontal transition. The deposit is overlain by moraine but underlying material is not visible. Similar deposits are not known from any other parts of the island. Although it is primary deposit and must therefore have been produced by an eruption on Heard Island, the location of its originating vent is not known.

December 1986-January 1987 activity. A deep, well-formed crater at the top of Mawson Peak was discovered on helicopter overflights in December 1986 and January 1987, during the 1986/87 Heard Island ANARE. On 21 December, a brief landing was made on the summit beside the crater. The crater was cylindrical and, from visual estimates, ~40-50 m in diameter and 50-70 m deep, with vertical walls exposing dark horizontal ash layers thinly coated in yellow sulfur. The crater was floored by a black ropy lava surface in which small patches of red lava periodically appeared, indicating an active lava lake within the crater. Larger red patches, ~ 5-10 m across, appeared less frequently, accompanied by gentle emissions of a little blue smoke. Minor steam emission also occurred from around the crater rim and from a rocky area on the crater's E side. The crater appears to have been formed by the 1985/87 eruption because it was not seen by climbing parties that reached the summit of Mawson Peak in 1965 and 1983.

A new pahoehoe lava flow in a glacial valley on Mawson Peak's SW flank was also discovered during the 1986/87 ANARE. The flow extended ~8-9 km from the summit crater rim, where it exited through a deep V-shaped notch, to within 2-3 km of the coast (near Cape Arkona). Small amounts of steam emanated from parts of the flow, which probably formed in January 1985, as observed from the Marion Dufresne.

1992 summit activity. Satellite images and observations from the ANARE base revealed eruptive activity in 1992. Data from the NOAA 11 polar orbiter showed plumes extending 300 km NNE then E from the island on 17 January at about 1720, and 200 km NE the next day at 0300. Weather in the region is usually cloudy, and no other activity was evident . . . until a short-lived thermal anomaly was detected on 18 May at 2146. The ANARE team had not yet reached Heard Island on 17 January, but the summit area was visible for 20 days in March, 18 days in April, and 7 days in May (as of the 29th). Gas had been emerging from the summit during fieldwork in mid-1990, but no activity was evident in 1992 until 29 May, when an orange glow was first noticed above the mountain at 2130. The glow rapidly intensified and appeared to be pulsating, faded after about a minute, then reappeared a few minutes later. Three or four such cycles were observed, with glow intensity changing randomly. Glow faded for the last time at about 2200. Although some auroral activity occurred that night, none of the observers believed that it was the source of the glow. Activity was next reported on 8 June, when vapor began to emerge from the summit at about 1430, soon forming a plume to the SE. Mist soon obscured the activity. Traces of steam were also visible on 10 June.

Reference. Barling, J., 1990, Heard and McDonald Islands, in Le Masurier, W., and Thomson, J., eds., Volcanoes of the Antarctic Plate and southern Oceans: American Geophysical Union, Washington DC, p. 435-441.

Further References. Barling, J., Goldstein, S.L., and Nicholls, I.A., 1994, Geochemistry of Heard Island (southern Indian Ocean): characterisation of an enriched mantle component and implications for enrichment of sub-Indian Ocean mantle: Journal of Petrology, v. 35, p. 1017-1053.

Hilton, D.R., Barling, J., and Wheller, G.E., 1995, Effect of shallow-level contamination on the helium isotope systematics of ocean-island lavas: Nature, v. 373, p. 330-333.

Information Contacts: G. Wheller, CSIRO Division of Exploration Geoscience, Australia; R. Varne, Univ of Tasmania; A. Vrana, K. Green, and T. Jacka, Australian Antarctic Division, Tasmania; W. Gould, NOAA/NESDIS.

December 1992 (BGVN 17:12) Cite this Report

New lava flow on SW flank

Evidence of recent eruptive activity was observed by Rod Ledingham, a geologist aboard the cruise ship Kapitan Klebnikov, during a visit . . . in mid-January. Lava had emerged from a new wedge-shaped graben-like feature that extended roughly 150 m down the summit cone's SW flank (figure 2). The flow had divided into two lobes and advanced to below 1,400 m elevation, apparently along approximately the same path taken by the 1985-87 lava. Steam rose from its distal end, but the central part of the flow appeared to be lightly snow-covered. A narrow plume rose from the summit crater, and the area from there E to the caldera wall was covered with gray ash. Vapor was also rising from a fissure roughly 100 m below the summit.

A team of five biologists has been on the island for ~14 months, but weather conditions are poor and the start time of the eruption is uncertain. Attila Vrana, head of the team, reported a strongly felt earthquake on 19 December that was not documented by the Worldwide Standardized Seismic Net.

Information Contacts: P. Quilty, Australian Antarctic Division, Tasmania.

February 1998 (BGVN 23:02) Cite this Report

No evidence of recent activity in March

During 18-21 March geologists sampled Holocene lava flows on Heard Island. On beaches of the N Laurens Peninsula, they found fresh pumice ranging in size up to about 20 x 20 cm . The pumice was concentrated among other storm- transported debris a little distance above the normal surf zone and appeared to have been deposited by wave action. Light creamy green to pale gray in color, the pumice had angular, ovoid or flattened shapes and contained predominantly microphenocrysts and occasional phenocrysts visible to the naked eye. Lithic fragments were not observed.

On Heard Island, Big Ben's summit was usually obscured by clouds. The summit was visible on 20 March, however, and at this time no evidence of recent volcanic activity was observed at Mawson Peak, Big Ben's recently active crater (figure 3). Similarly no plume was seen coming from Heard when McDonald vented steam in early April. In accord with these observations, scientists inferred that the December 1996-January 1997 volcanic activity attributed to Heard actually denoted activity at McDonald.

References. LeMasurier, W.E., and Thompson, J.W., primary eds., 1990, Volcanoes of the Antarctic Plate and Southern Oceans, Antarctic Research Series: American Geophysical Union, Washington, D. C. (ISBN 0066-4634).

Collerson, K. D., 1997, Field studies at Heard and McDonald Island in March 1997: unpublished Australian National Antarctic Research Expedition (ANARE) report.

Information Contacts: Kenneth Collerson, Department of Earth Sciences, University of Queensland, Brisbane, Queensland 4072, Australia; Kevin Kiernan, Department of Geography and Environmental Sciences, University of Newcastle, Newcastle, New South Wales 2300, Australia; Richard Williams, Australian Antarctic Division, Channel Highway, Hobart, Tasmania, Australia; Andrew Tupper, Northern Territory Regional Forecasting Centre, Bureau of Meteorology, P. O. Box 735, Darwin, Northern Territory 0801, Australia.

November 2000 (BGVN 25:11) Cite this Report

Discovery of a distinct vent below Mawson Peak; brown fumes in November

Activity from Mawson Peak, a discrete volcanic cone that lies atop Big Ben stratovolcano, was observed by the Australian National Antarctic Research Expedition (ANARE) during October-November 2000. Frequent cloud cover obscured Big Ben.

On 19 October, workers observed several hours of fumarolic activity from the RSV Aurora Australis while 2-3 km off the N shore of Heard Island between Corinthian and Spit Bays. Gaseous emissions were rising at least 200 m above the summit. During the early morning of 20 October, those aboard the ship observed similar continuing activity until clouds obscured the view. From the Red Island area at the W end of Heard Island, on 28 October strong fumarolic activity was seen emanating from the summit of Mawson Peak. Observers suggested the presence of a second emission point on the S slopes 100-200 m below the summit.

On 9 November, a helicopter flyover of Mawson Peak revealed that the crater and lava lake observed in 1987 were no longer visible. Instead, the summit had the form of a steep, irregular ice dome with gases venting through its apex (figure 4). The flyover also confirmed an apparently distinct area of activity 150-200 m below Mawson Peak near the head of Lied Glacier (Kiernan and McConnell, 2000). This newly discovered area was separated from the summit vent by several hundred meters of clean, white ice.

Reports of more than one red glow source from the 1950-52 and 1985 eruptive events hinted at the possible existence of a second vent on Big Ben (ANARE Station Reports, and Neumann van Padang, 1963). Recent failure to locate such a vent led Quilty and Wheller (2000) to conclude that the previously observed multiple red glows were attributable to magma ponded in the summit crater and lava flowing down Big Ben's flanks. Current observations, however, now suggest the presence of a separate, lower vent in the vicinity of the 1985 flow.

On 13 November observers from Fairchild Beach on the N coast of Heard Island noted brown fumes venting from the summit area. The following day, fumarolic activity was observed from a vantage point on the E moraine of Browns Glacier Lagoon on the N coast.

References. Kiernan, K., and McConnell, A., 2000, ASAC Project 1118, Geomorphological Evolution of Heard Island: Report to Atlas Cove Station Leader, ANARE.

Neumann van Padang, M., 1963, Arabia and the Indian Ocean: Catalogue of the Active Volcanoes of the World, v. 16, p. 1-64.

Quilty, P.G., and Wheller, G., 2000, Heard Island and the McDonald Islands: A window on the Kerguelen Plateau: Papers & Proceedings of the Royal Society of Tasmania, v. 133, no. 2, p. 1-12.

Information Contacts: Kevin Kiernan, Geography and Environmental Studies, University of Tasmania, GPO Box 252-79, Hobart TAS 7001, Australia.

February 2001 (BGVN 26:02) Cite this Report

Increased fumarolic activity in February and March 2001; possible lava flow

Fumarolic activity emanating from Big Ben stratovolcano on Heard Island increased since the previous report period of October-November 2000 (BGVN 25:11). Both the vent at the summit of Mawson Peak and the second, recently confirmed vent downslope from the summit, were involved in the activity in early February 2001.

At about 2100 on 2 February an increased emission of volatiles was observed from Atlas Cove, located ~15 km NW of the summit where the main island connects with the Laurens Peninsula (see maps in SEAN 10:02 and BGVN 23:02). Under daylight the plume had a yellow-colored tinge. By midnight venting increased substantially. Observations continued until 0100 on 3 February when emissions appeared to diminish and clouds obscured the view. No lava or ejecta were observed from the Atlas Cove vantage point.

The plumes rose up to ~1,000 m in height, but tended to vary in extent over time. The precise points of emission were hidden by the high shoulder of Big Ben. Nevertheless, the emissions appeared to emanate from two discrete vents, one at Mawson Peak, and the other the newly discovered vent estimated to be 300-400 m vertically below it (lower than previously thought) on the S-facing slope.

Observations on the afternoon of 3 February revealed further abatement of volatile venting. Some workers suggested the presence of a third vent based on observations from Anzac Peak on Laurens Peninsula at the NW end of the island, but these findings are not yet substantiated. From a high point on Laurens Peninsula a black lava flow (?) on Mawson Peak was observed to be closer to the Atlas Cove side of the island than on previous visits. The possible flow was ~100 m wide and ~1,500 m long, but size estimates were hindered by distance, the enormity of Big Ben, the lack of any comparative scale, and the acute viewing angle.

On 5 March observers obtained good views of Big Ben from Red Island, at the farthest N tip of the Laurens Peninsula, but were unable to discern any summit activity despite clear conditions. Further observations from the same vantage point at 1330 on 7 March afforded a brief 5-8 minute view of the summit and revealed that a significant plume rose 100-200 m and drifted several kilometers downwind. The plume's width was estimated to be 50 m. The "black scar" first viewed on 3 February and interpreted as a plausible lava flow was again visible and appeared unchanged since its last observation.

The findings in early February and March 2001 are consistent with recent observations during a helicopter overflight of Big Ben that confirmed the presence of a vent well below the summit of Mawson Peak (Kiernan & McConnell, 2000). They compound the likelihood that more than one vent was involved in earlier eruptive activity during 1950-52 and 1985 (ANARE Station Reports; Neumann van Padang, 1963), contrary to recent conclusions by Quilty & Wheller (2000). Observations of volcanism on Heard Island, however, are limited because of its remoteness, and since the summit area is frequently shrouded in clouds. Hence, the general level of activity observed recently is difficult to assess.

References. Kiernan, K., and McConnell, A., 2000, ASAC Project 1118, Geomorphological Evolution of Heard Island: Report to Atlas Cove Station Leader, ANARE.

Neumann van Padang, M., 1963, Arabia and the Indian Ocean: Catalogue of the Active Volcanoes of the World, v. 16, p. 1-64.

Quilty, P.G., and Wheller, G., 2000, Heard Island and the McDonald Islands: A window on the Kerguelen Plateau: Papers & Proceedings of the Royal Society of Tasmania, v. 133, no. 2, p. 1-12.

Information Contacts: Stu Fitch and Andrew Lock, Australian Antarctic Division, Channel Highway, Kingston, TAS 7050, Australia (URL: http://www.antarctica.gov.au/); C.J. Klok, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa (URL: http://www.up.ac.za/zoology-entomology/); Kevin Kiernan and Anne McConnell, Geography & Environmental Studies, University of Tasmania, GPO Box 252-79, Hobart TAS 7001, Australia.

March 2001 (BGVN 26:03) Cite this Report

Photographs of upper slopes substantiate reports of activity from two distinct vents

Photographs taken during early February 2001 at Heard (BGVN 26:02) revealed the character and location of the activity there. Figures 5 and 6 were taken on the early morning of 3 February, shortly after midnight against a dark sky. Light from the active vents illuminated the overcast sky and Big Ben stratovolcano. The two distinct light sources pictured in figure 6 evidenced activity from two separate vents. No research-related visits to the remote Heard Island are planned in the immediate future.

References. Kiernan, K., and McConnell, A., 2000, ASAC Project 1118, Geomorphological Evolution of Heard Island: Report to Atlas Cove Station Leader, ANARE.

Neumann van Padang, M., 1963, Arabia and the Indian Ocean: Catalogue of the Active Volcanoes of the World, v. 16, p. 1-64.

Quilty, P.G., and Wheller, G., 2000, Heard Island and the McDonald Islands: A window on the Kerguelen Plateau: Papers & Proceedings of the Royal Society of Tasmania, v. 133, no. 2, p. 1-12.

Information Contacts: Stu Fitch, Australian Antarctic Division (AAD); Andrew Lock, AAD; C.J. Klok, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa; Kevin Kiernan and Anne McConnell, Geography & Environmental Studies, University of Tasmania, GPO Box 252-79, Hobart TAS 7001, Australia.

January 2003 (BGVN 28:01) Cite this Report

Infrared data show previously unknown activity during May-June 2000

Between 13 May 2000 and 30 January 2003, thermal alerts on Heard Island occurred on the following dates: 24 May; 3, 5, and 6 June; 25 September; 29 October; 5, 15, 19, and 24 November; 16, 17, 26, and 30 December 2000; and 2 February 2001 (figure 7). Since then no further thermal alerts have been recorded. There have been no reports of May-June 2000 activity on Heard Island published in the Bulletin. However, Rothery and Coppola are confident that the MODIS data prove high-temperature volcanic activity at these times. The late-2000 period of MODIS thermal alerts is substantiated by reports from ships and helicopters. The first of these, "fumarolic activity" on 19 October (BGVN 25:11), is 24 days later than the first MODIS thermal alert in this period. A fresh lava flow was suspected but unproven on 3 February (BGVN 26:02), and two incandescent vents were photographed on the same day (BGVN 26:03). The interpretation of the MODIS data is that lava effusion is likely. The locations of the alert pixels (figure 8) suggest that activity was on the WSW side of the summit, and may have extended about halfway to the shore.

Reference. Barling, J., 1990, Heard and McDonald Islands, in Le Masurier, W., and Thomson, J., eds., Volcanoes of the Antarctic Plate and southern Oceans: American Geophysical Union, Washington DC, p. 435-441.

Information Contacts: David A. Rothery and Diego Coppola, Department of Earth Sciences, The Open University, Milton Keynes MK 6AA, United Kingdom.

December 2004 (BGVN 29:12) Cite this Report

Thermal alerts indicate crater lake activity starting in June 2003 until June 2004

Infrared satellite data triggered MODVOLC thermal alerts between 24 May 2000 and 2 February 2001 (BGVN 28:01). A new series of alerts began on 9 June 2003, with frequent alerts continuing until 14 June 2004. The cloud-free ASTER imagery from June 2003 to June 2004 was examined, and although it does not offer very complete coverage of this new phase of activity, all the images contained very small anomalies (just a few pixels) in the central crater. This suggests that most of these alerts are due to increased activity at the lava lake, with no indication of lava flows. Also, all the 2003-2004 MODVOLC anomalies were 1-2 pixels (no elongate thermal anomalies), further suggesting that this is local central-vent activity.

Information Contacts: Matt Patrick, Luke Flynn, Harold Garbeil, Andy Harris, Eric Pilger, Glyn Williams-Jones, and Rob Wright, HIGP Thermal Alerts Team, Hawai'i Institute of Geophysics and Planetology (HIGP) / School of Ocean and Earth Science and Technology (SOEST), University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).

May 2006 (BGVN 31:05) Cite this Report

2006 imagery indicates renewed volcanism

Matt Patrick observed from MODIS (Moderate Resolution Imaging Spectroradiometer) images analyzed by the HIGP MODVOLC algorithm that relatively new activity began in March 2006 at Heard Island. Two isolated alerts occurred on 11-12 March 2006, and sustained alerts occurred from 7-18 May, 28 May-5 June, and 13-20 June (table 1). Alerts were 1-3 pixels in size. The pixel locations all appeared to be clustered generally near the summit of Big Ben, suggesting central vent (lava lake?) activity rather than lava flows. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images over the last several months have all been cloudy and therefore unable to reinforce or support the MODVOLC results. However, a nighttime ASTER image on 29 May 2006 at 0110 showed the new activity (figure 9).

Table 1. MODVOLC alerts for 2006 through 21 June. Courtesy of Hawai'i Institute of Geophysical and Planetology (HIGP) Thermal Alerts Team.

Date	Time (local)	Pixels	Satellite
11 Mar 2006	2315	1	Terra
12 Mar 2006	0100	2	Aqua
07 May 2006	0100	1	Terra
07 May 2006	2305	1	Terra
08 May 2006	0150	1	Aqua
09 May 2006	2255	1	Terra
10 May 2006	0140	1	Aqua
11 May 2006	2335	1	Terra
18 May 2006	2250	2	Terra
28 May 2006	2325	1	Terra
29 May 2006	0110	2	Aqua
02 Jun 2006	2345	3	Terra
03 Jun 2006	0130	2	Aqua
05 Jun 2006	0115	1	Aqua
13 Jun 2006	2325	2	Terra
14 Jun 2006	0110	4	Aqua
15 Jun 2006	0010	2	Terra
16 Jun 2006	0100	1	Aqua
20 Jun 2006	2330	1	Terra

The previous phases of activity spanned May 2000-February 2001 and June 2003-June 2004 (BGVN 29:12).

Information Contacts: Matt Patrick, HIGP Thermal Alerts Team, Hawai'i Institute of Geophysics and Planetology (HIGP) / School of Ocean and Earth Science and Technology (SOEST), University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Andrew Tupper, Darwin Volcanic Ash Advisory Centre, Bureau of Meteorology, Australia.

November 2006 (BGVN 31:11) Cite this Report

ASTER images show hotspot for possible lava lake and flow 8 December

Matt Patrick reported that Heard Island continued to display evidence of activity in its summit crater (continuing the phase which began in May 2006, BGVN 31:05). Figure 10 presents an ASTER image (Bands 9-3-2) from 8 December 2006 showing a hotspot at the summit, presumably a lava lake, with a recently emplaced lava flow extending 700 m E.

Table 2 lists the thermal anomalies recorded by the Hawai'i Institute of Geophysics and Planetology (HIGP) during 25 June 2006 (as last reported in the BGVN 31:05) to mid December 2006. The table lists 27 thermal anomalies during 25 June to 15 December 2006. There is no MODVOLC thermal anomaly on 8 December, the date of the ASTER image in the previous figure.

Table 2. Thermal anomalies from mid-June to mid-December 2006 from MODIS satellites. Courtesy of HIGP Thermal Alerts Team.

Date	Time (UTC)	Pixels	Satellite
25 Jun 2006	1850	1	Terra
17 Jul 2006	2000	1	Aqua
06 Aug 2006	1935	1	Aqua
13 Aug 2006	0425	1	Terra
13 Aug 2006	1755	1	Terra
13 Aug 2006	1940	1	Aqua
15 Aug 2006	1930	1	Aqua
22 Aug 2006	1935	2	Aqua
10 Sep 2006	1820	2	Terra
12 Sep 2006	1805	1	Terra
20 Sep 2006	0930	1	Aqua
21 Sep 2006	1800	1	Terra
21 Sep 2006	1950	1	Aqua
11 Oct 2006	1735	1	Terra
11 Oct 2006	1925	2	Aqua
24 Oct 2006	0920	1	Aqua
27 Oct 2006	1735	2	Terra
27 Oct 2006	1925	1	Aqua
02 Nov 2006	1835	1	Terra
07 Nov 2006	1715	2	Terra
07 Nov 2006	1905	4	Aqua
17 Nov 2006	0830	1	Aqua
24 Nov 2006	0430	2	Terra
25 Nov 2006	0920	1	Aqua
26 Nov 2006	1750	2	Terra
15 Dec 2006	1820	1	Terra
15 Dec 2006	2005	1	Aqua

Matt Patrick noted that it is not surprising that the ASTER image showed a thermal anomaly but MODVOLC did not. First, because ASTER has infrared bands at 30-90 m, it is inherently more sensitive to thermal anomalies than the 1-km MODIS bands (MODVOLC uses MODIS data). Second, the MODVOLC algorithm has a threshold which sometimes disregards low-level eruptive activity in order to avoid false alarms. The anomaly in the ASTER image was not particularly large or intense, so it is not surprising it did not show up in MODVOLC.

Information Contacts: Matthew Patrick, Dept. of Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA; Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts Team, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).

March 2007 (BGVN 32:03) Cite this Report

Thermal anomalies ~300 m apart may suggest two vents

An ASTER image over Heard for 29 February 2007 (figure 11) was found by Matt Patrick in which two thermal anomalies are shown, separated by ~ 300 m. The anomaly to the SE appeared to be a new feature, representing either a distinct vent or a hot distal portion of an active flow from the main vent. There are no anomalous shortwave pixels between the two anomalies as one might expect for an active lava surface, but the flow may be channeled underground between the anomalies. The total lack of anomalous pixels in the region between the two anomalies, however, caused Patrick to suspect that this is a distinct vent. If this is a distinct vent, it would be the first clear illustration of multiple vents at Heard. None of the previous images Patrick has studied covering the last 6 years (including the 8 December 2006 image, also using Band 9-3-1 color mapping, shown in figure 12) showed indications of a secondary anomaly.

MODIS satellite data also revealed thermal anomalies on 24 different days between 27 December 2006 and 6 April 2007 (table 3).

Table 3. Thermal anomalies at Heard from mid-December 2006 to early April 2007 from MODIS satellites. Continued from table in BGVN 31:05. Courtesy of Hawai'i Institute of Geophysics and Planetology (HIGP) Hot Spots System.

Date	Time (UTC)	Pixels	Satellite
27 Dec 2006	1845	1	Terra
29 Dec 2006	1830	1	Terra
31 Dec 2006	1820	2	Terra
31 Dec 2006	2005	1	Aqua
09 Jan 2007	1815	2	Terra
19 Jan 2007	1850	1	Terra
04 Feb 2007	1900	1	Aqua
05 Feb 2007	1940	1	Aqua
07 Feb 2007	1930	2	Aqua
16 Feb 2007	1925	1	Aqua
21 Feb 2007	1940	1	Aqua
26 Feb 2007	0445	1	Terra
05 Mar 2007	1820	2	Terra
07 Mar 2007	1810	1	Terra
11 Mar 2007	1745	1	Terra
12 Mar 2007	1825	2	Terra
12 Mar 2007	2015	1	Aqua
14 Mar 2007	1815	1	Terra
14 Mar 2007	2000	2	Aqua
18 Mar 2007	1935	1	Aqua
20 Mar 2007	1925	1	Aqua
24 Mar 2007	1850	1	Terra
26 Mar 2007	0505	1	Terra
27 Mar 2007	1745	2	Terra
28 Mar 2007	2015	2	Aqua
29 Mar 2007	1920	1	Aqua
06 Apr 2007	0450	1	Terra

Information Contacts: Hawai'i Institute of Geophysics and Planetology (HIGP) Hot Spots System, University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Matthew Patrick, Dept. of Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA.

June 2007 (BGVN 32:06) Cite this Report

Eruption ends in April; three eruptions of more than 11 months long since 2000

Based on Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System MODVOLC analysis of MODIS (Moderate Resolution Imaging Spectroradiometer) satellite thermal anomaly data, Matt Patrick reported in June 2007 that the eruption at Heard that started about a year ago (BGVN 31:05, 31:11, and 32:03) seemed to have ceased. Due to its isolated location, Heard Island is rarely visited, and satellite imagery provides the only regular information on eruptive activity. There have been three eruptive periods of 11 months or longer during which thermal anomalies were frequent since MODIS data came online in early 2000 up to 21 July 2007 (table 4).

Table 4. Summary of eruptive episodes at Heard based on MODVOLC analyses of MODIS thermal satellite data. Courtesy of Matt Patrick.

Eruption	First Anomaly	Last Anomaly	Duration	Comments
2000-2001	07 Mar 2000	02 Feb 2001	332 days	857 days until next eruption. An earlier report (BGVN 28:01) indicated that this eruption began in May 2000, while Patrick's data indicated that MODIS thermal alerts began in March 2000.
2003-2004	09 Jun 2003	14 Jun 2004	371 days	635 days until next eruption.
2006-2007	11 Mar 2006	06 Apr 2007	391 days	A single anomaly on 11-12 March 2006 was followed by lack on anomalies until 6 May, when they became frequent. (Note: since 6 April 2007, only one, single-pixel anomaly has been measured--24 July 2007. Patrick concluded that the 2006-2007 eruptive phase of nearly daily alerts ended on 6 April 2007.)

A graph prepared by Patrick and the HIGP Thermal Alert System Team (figure 13) showing radiant heat output and distance of alert pixels from the volcano vent (1 pixel=1 km) also shows the three separate eruptions since 2000. Pixel distances determined from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and the MODVOLC alert show that activity during all three eruptions was centered around the summit crater, with sporadic lava flows during the 2000-2001 and 2006-2007 episodes. Only the 2000-2001 eruption clearly featured long (i.e. several kilometer long) lava flows, as shown by the > 3 km distance in July 2000 (figure 13). Patrick noted that a 2-km-long lava flow seen in Landsat imagery early in the 2000 eruption, on 7 July 2000 (figure 14), was detected by MODVOLC on 10 July 2000. However, since the location of the MODVOLC alerts from that time period were not far from the source vent, the alerts were not effective for showing the length of the lava flow.

The 2003-2004 and 2006-2007 activity appeared to be largely limited to the summit crater, as indicated by the small MODVOLC distances (i.e. 1 km or less, with 1 km being the size of the pixels and inherent uncertainty) and ASTER data examined. ASTER data did show a possible 900-m-long flow to the SW of the vent in May 2006 (BGVN 31:05 and 31:11) and a clear 700-m-long flow of lava extending NE of the summit crater in December 2006, indicating that small effusive events have occurred in addition to central vent activity in the 2006-2007 phase. Patrick has not observed to this time any obvious ash plumes in the ASTER images, but all of the images examined appeared to be partly cloudy.

Patrick noted that it is difficult to determine exactly how often thermal anomalies for Heard Island may be completely obscured by clouds. The benefit of MODIS is the 1-2 observations per day, so that if activity is indeed present, it should not elude detection for very long. In the MODVOLC plot (figure 13), there were fairly regular alerts over the course of a year or so at a time, during which there must have been some cloud cover.

Information Contacts: Matt Patrick, Dept. of Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA; Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Earth Observatory (URL: http://earthobservatory.nasa.gov/NaturalHazards/).

January 2008 (BGVN 33:01) Cite this Report

Rare thermal anomalies through March 2008 suggest eruptions

Due to its isolated location in the S Indian Ocean on the Kerguelen Plateau, Heard Island is rarely visited, and satellite imagery provides the only regular information on eruptive activity. The Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System MODVOLC provides an analysis of MODIS (Moderate Resolution Imaging Spectroradiometer) satellite thermal anomaly data, with 1-2 daily observations. That system remains the best source of evidence at isolated, glacier-covered volcanoes like Heard, though it is difficult to determine how often meteorological clouds may obscure thermal anomalies.

The last report summarized activity beginning in March 2000 (BGVN 32:06), describing three eruptive episodes (based on thermal anomalies). The last thermal anomaly mentioned was on 6 April 2007. As seen on table 5, the MODVOLC system recorded the next thermal anomaly on 24 July 2007. For the rest of 2007, there were anomalies recorded on two days in August and two days in November. During 2008 as late as 2 March, anomalies occurred in February and March.

Table 5. Thermal anomalies measured by MODIS/MODVOLC over Heard Island during 7 April 2007 through 2 March 2008. Courtesy of HIGP Thermal Anomalies Team.

Date	Time (UTC)	Pixels	Satellite
24 Jul 2007	1750	1	Aqua
12 Aug 2007	1820	1	Terra
30 Aug 2007	1955	1	Aqua
11 Nov 2007	1800	1	Terra
11 Nov 2007	1945	2	Aqua
22 Feb 2008	1955	3	Aqua
02 Mar 2008	1950	1	Aqua

Information Contacts: Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).

September 2010 (BGVN 35:09) Cite this Report

Quiet, with minor thermal anomalies, since March 2008

According to Matt Patrick (USGS) in a report dated 25 October 2010, satellite imagery has not detected unambiguous eruptive activity at Heard since March 2008. No MODVOLC thermal anomalies have been detected since that time, and recent cloud-free ASTER images generally lacked indications of eruptive activity. Given Heard's isolation, satellite imagery provides the only regular information on its behavior. As previously reported, numerous anomalies had been noted in 2006 and 2007, clearly indicating eruptions (BGVN 31:05, 31:11, 32:03, and 32:06). Rare thermal anomalies were recorded through 2 March 2008, with sufficient radiance and extent to suggest eruptions (BGVN 33:01).

Patrick found recent ASTER images that include faint thermal anomalies. The anomalies appeared at Big Ben volcano's Mawson Peak, which is both the volcano's and the island's summit, and hosts the active vent. The most recent cloud-free image, taken on 25 February 2010 (figure 15), shows a small (2-3 pixels in size) thermal anomaly, indicating either very low-level activity or simply warm ground in and around the vent.

Information Contacts: Matthew R. Patrick, Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawai'i National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/); Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer), Earth Remote Sensing Data Analysis Center (ERSDAC) in Japan, and the Jet Propulsion Laboratory in the U.S. (URL: http://asterweb.jpl.nasa.gov/).

January 2013 (BGVN 38:01) Cite this Report

Satellite imagery reveals lava flows in December 2012

We received an informal report from Matt Patrick (Hawaiian Volcano Observatory) on a new eruptive episode at Big Ben volcano, Heard Island (figure 16). He noted that MODVOLC thermal alerts reappeared at Heard in September 2012 after a four year hiatus (the last eruptive episode ended on 2 March 2008; BGVN 33:01), suggesting the start of a new eruptive episode at the volcano. Since Heard Island is unsettled and extremely isolated, monitoring of the volcano is possibly primarily through satellite imagery (Patrick, 2013).

EO-1 Advanced Land Imager images collected through late 2012 and early 2013 confirm that eruptive activity resumed around September 2012, in the form of a low-level effusive style eruption similar to its other recent eruptions (figures 17 and 18). Patrick noted that the vent crater had enlarged significantly over the four years following the end of the last eruptive phase, March 2006-March 2008.

The 15 December 2012 image in figure 17 shows that a short lava flow from the summit was emplaced on the SW flank. The flow was ~420 m long and had two lobes. By 28 December, a flow consisting of two lobes (presumably the same flow as in the 15 December image) had reached 770 m SW of the summit crater. In the 5 January 2013 image this flow was 780 m long and had changed little over the previous week.

Figure 18 shows that the 9 September and 13 October 2012 images suggested active lava contained with the summit crater. The 15 and 28 December 2012 images showed elevated temperatures on the lava flow SW of the summit, suggesting it was active over this interval, which was consistent with the observed elongation of the flow in the visible images. Fewer high-temperature pixels in the 5 January 2013 image and the meager advancement observed in the visible images, suggested that the flow had stalled by this point.

Overall, the activity as of mid-March 2013 had consisted of lava within the crater and a lava flow of at least 770 m long emplaced SW of the crater. This low-level effusive activity is consistent with the previous three eruptive episodes observed in satellite images at Heard Island (Patrick and Smellie, in review). These three episodes, May 2000-November 2001 (BGVN 25:11, 26:02, 26:03, and 28:01), June 2003-July 2004 (BGVN 29:12), and March 2006-March 2008 (BGVN 31:05, 31:11, 32:03, 32:06, 33:01, and 35:09), each lasted 1-2 years. On this basis, Patrick suggested that this new eruptive episode may persist for a similar duration. MODVOLC thermal alerts were measured nearly continuously from 21 September 2012 through 24 February 2013.

References. Patrick, M., 2013, A new eruptive episode at Big Ben Volcano, Heard Island, informal communication to BGVN, 23 February 2013.

Patrick, M.R., and Smellie, J.L., in review, A spaceborne inventory of volcanic activity in Antarctica and southern oceans, 2000-2010, Antarctic Science, in review in 2013.

Information Contacts: Matt Patrick, Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawai'i National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/); Australian Antarctic Data Centre, Department of the Environment and Heritage, Commonwealth of Australia (URL: https://data.aad.gov.au/database/mapcat/heard/heard_island.gif); MODVOLC, Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).

August 2013 (BGVN 38:08) Cite this Report

Satellite thermal alerts continue to early October 2013

[A previous report (BGVN 38:01) provided] information from Matt Patrick of the Hawaiian Volcano Observatory (HVO) on the onset of thermal alerts measured by satellites for Heard Island (see map in BGVN 38:01) in September 2012 after a 4-year hiatus. MODIS/MODVOLC measured thermal alerts fairly regularly from 21 September 2012 through 6 October 2013, with the greatest number of days with measured thermal alerts in December 2012 and March 2013.

In a satellite image acquired by NASA Earth Observatory on 13 October 2012 (figure 19), Heard Island is covered in [clean snow and glacial ice, and Mawson Peak appears quiet....] By 7 April 2013 Mawson's steep-walled summit crater had filled, and a trickle of lava had spilled down the volcano's SW flank (figure 20). On 20 April (figure 21), the lava flow remained visible, and had even widened slightly just below the summit.

Satellite inventory, 2000-2010. Patrick and Smellie (2013) recently published an article on a 10-year (2000-2010) spaceborne inventory of volcanic activity in Antarctica and southern oceans, including Heard Island. They noted that MODVOLC alerts indicated that eruptive activity at Heard Island comprised three sustained episodes during the decade; 24 May 2000-2 February 2001, 9 June 2003-June 2004, and 11 March 2006-2 March 2008. "Throughout the first two eruptions and their subsequent repose intervals, the summit vent was small, and less than 100 m wide... At some time in 2008 or early 2009 ... the summit crater widened to 200 m." Also, the authors noted that "the activity at Heard Island was entirely effusive and there is no evidence for any low-level explosive activity" during the study decade. The article notes that a limiting factor for satellite monitoring in this region is persistent cloud cover, although tall volcanoes such as Big Ben on Heard Island often have their summits above the cloud cover, resulting in "a higher rate of cloud-free views."

Reference. Patrick, M.R., and Smellie, J.L., 2013, Synthesis: A spaceborne inventory of volcanic activity in Antarctica and southern oceans, 2000-10, Antactic Science, v. 25, no. 4, p. 475-500, doi:10.1017/S0954102013000436.

Information Contacts: Matt Patrick, Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawai'i National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/); NASA Earth Observatory (URL: http://earthobservatory.nasa.gov/); MODIS/MODVOLC, Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).

August 2016 (BGVN 41:08) Cite this Report

Intermittent thermal activity during 2013-14; plumes detected in 2015 and early 2016

Thermal activity detected by MODIS (Moderate Resolution Imaging Spectroradiometer) recorded by the MODVOLC system occurred regularly from 21 September 2012 through 6 October 2013 (BGVN 38:08). This report covers thermal alerts and anomalies from the remainder of 2013 through March 2016, and describes the observations of two plumes, one by satellite image on 30 October 2015, and the other by scientists aboard a research vessel during 30-31 January 2016.

Thermal anomalies continued to be seen in MODIS data between October 2013 and 21 July 2014, and again on 16 November 2014, due to a persistent lava lake and possible lava flows. According to a NOAA National Environmental Satellite, Data, and Information Service (NESDIS) scientist, thermal anomalies seemingly on the E flank were detected in Visible Infrared Imaging Radiometer Suite (VIIRS) satellite images during 2-30 November 2014. Dense cloud cover prevented views during 1-2 December.

The frequency of MODVOLC alerts decreased in 2015, with the exception of frequent alerts during June and July 2015, with a single alert on 31 December. In early 2016 there were alerts measured on 28 January and 21 February.

A plume from Heard was visible in a U.S. Air Force satellite image drifting SSW on 30 October 2015. Data provided by Middle InfraRed Observation of Volcanic Activity (MIROVA) show frequent moderate thermal anomalies that tapered off after September 2015. MIROVA data also show that the frequent anomalies occurred farther from the summit during the early to mid-portion of 2015 (figure 22).

During 30-31 January 2016, scientists and crew aboard CSIRO's (Commonwealth Scientific and Industrial Research Organisation) Marine National Facility research vessel Investigator circled the island and observed a plume rising from Mawson Peak's crater and lava flows traveling down the NW flanks (figure 23). Visual observations are very rare due to its remote location. A MODVOLC thermal alert on 28 January was likely due to the lava emissions.

Information Contacts: Marine National Facility, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Hobart, Tasmania, Australia (URL: http://mnf.csiro.au/, https://blog.csiro.au/big-ben-erupts/); Michael J. Pavolonis, NOAA/NESDIS Center for Satellite Applications and Research (STAR), Advanced Satellite Products Branch (ASPB), Madison, Wisconsin, USA (URL: https://www.star.nesdis.noaa.gov/star/aspb_index.php); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/, http://modis.higp.hawaii.edu/cgi-bin/modisnew.cgi); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); United States Air Force, 557th Weather Wing, Weather Intel Flight, 2 WS/WXI Offutt AFB, NE 68133, USA.

October 2017 (BGVN 42:10) Cite this Report

Expedition visit in March-April 2016, intermittent eruptive activity through September 2017

The remote island of Heard in the southern Indian Ocean is home to the Big Ben stratovolcano, which has had confirmed intermittent activity since 1910. The nearest continental landmass, Antarctica, lies over 1,000 km S. Visual confirmation of lava flows on Heard are rare; thermal anomalies detected by satellite-based instruments provide the most reliable information about eruptive activity. Thermal alerts reappeared in September 2012 after a four-year hiatus (BGVN 38:01), and have been intermittent since that time. Information comes primarily from MODVOLC and MIROVA thermal anomaly data, but Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) also provides reports from research expeditions. The independent March-April 2016 Cordell Expedition also provided recent ground-based observations mentioned in this report, which covers activity through September 2017.

Expeditions during January-April 2016. Scientists aboard the CSIRO Research Vessel Investigator observed an eruption of Big Ben on 31 January 2016. Vapor was seen emanating from the peak and lava flowed down the flank over a glacier (see figure 23, BGVN 41:08, and video link in Information Contacts). The research team, lead by the University of Tasmania's Institute for Marine and Antarctic Studies (IMAS), was conducting a study of the link between active volcanoes on the seafloor and the mobilization of iron by hydrothermal systems which enriches and supports life in the Southern Ocean.

During a private expedition from 22 March to 11 April 2016, scientists and engineers from the 2016 Cordell Expedition documented changes to the island and its life since a prior visit in 1997, and tested radio operations. On 23 March the team was able to photograph the usually cloud-covered Mawson Peak, the summit of Big Ben (figure 24). Steam was visible above the flat upper surface, possibly a crater rim or fissure. They estimated a height of about 45 m of an edifice rising above the adjacent slope. The ground at the site of the team campsite, near Atlas Cove on the NW side of the island, was covered with lava flows (figure 25). While the expedition had to cancel a planned expedition to the summit, rocks collected from the shoreline confirmed the diversity of volcanic rocks on the island (figure 26).

At the southern end of Sydney Cove, near Magnet Point on the northern tip of Laurens Peninsula (the NW side of the island), the team identified a small islet, with dimensions of about 40 x 120 m and nearly vertical sides about 100 m high. Columnar jointing in the volcanic rocks is well exposed at the base and on the nearly flat upper surface (figure 27).

Satellite thermal and visual data, 2012-2017. The most consistent source of information about eruptive activity at Heard comes from satellite instruments in the form of visual and thermal imagery, and thermal anomaly detection. From the time that renewed activity was detected in MODVOLC data in late September 2012 through September 2017, either the MODVOLC or MIROVA systems have consistently detected thermal signals, with only a few short breaks. A four-month span from mid-July to mid-November 2014, and a two-month gap during February and March 2015 are the only periods longer than a month when no thermal signal was reported. Continuous MIROVA information from late January 2016 through September 2017 shows intermittent but persistent thermal anomalies throughout the period (figure 28).

The moderate signal at the very end of January 2016 coincides with the CSIRO expedition observing the lava flows on the flank of Big Ben. Low-level MIROVA anomalies were recorded in April and early May 2016. Activity picked up during June, and strengthened through July and August 2016. Late September through November 2016 was a period with heightened activity as well. From December 2016 through August 2017, intermittent low-to-moderate intensity anomalies were recorded every month. Activity appeared to increase briefly during early February and September 2017. On 4 February 2017, Landsat 8 captured a rare clear view that showed fresh lava and debris flows emanating from the summit on top of the snow (figure 29). The longest flow is estimated to be 1,300 m long. False-color infrared imagery of the same image of Mawson Peak also reveals two vents separated by about 250 m (figure 30). Subsequent imagery on 20 and 27 February also detected thermal anomalies at the summit. The visual imagery of the lava flows on 4 February 2017 corresponds to the early February spike in MIROVA thermal anomaly data.

Information Contacts: Commonwealth Scientific and Industrial Research Organisation (CSIRO) (URL: http://www.csiro.au/); CSIROscope, CSIRO Blog, Big Ben Erupts: Australia's active volcano cluster blows its lid (URL: https://blog.csiro.au/big-ben-erupts/); Robert W. Schmieder, 2016 Cordell Expedition, 4295 Walnut Blvd., Walnut Creek, CA 94596, Post Expedition report to the Australian Antarctic Division (AAD) (URL: http://www.cordell.org/, http://www.heardisland.org/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); Bill Mitchell, The Inquisitive Rockhopper, Big Ben eruption update 2017-02-27 (URL: https://inquisitiverockhopper.wordpress.com/2017/02/).

January 2018 (BGVN 43:01) Cite this Report

Intermittent low-to-moderate thermal anomalies end in mid-November 2017

The most recent eruptive period at Heard began in September 2012 (BGVN 38:01). Direct observations are rare at this remote volcano, but the presence of lava flows can frequently be discerned using infrared satellite data. Thermal anomalies were intermittent, with some episodes of clearly stronger activity, during 2016 and through September 2017 (BGVN 42:10).

During all of 2017, MODIS infrared satellite data analyzed using the MODVOLC algorithm showed anomalies near the summit only on 2, 16, and 26 September, and on 1 and 22 October. The MIROVA system also detected numerous hotspots within 5 km of the volcano through late October. One additional significant anomaly was identified on approximately 12 November 2017 (figure 31). No further significant anomalies were noted through February 2018.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).

October 2018 (BGVN 43:10) Cite this Report

Thermal hotspots persist at Mawson Peak, lava flows visible in satellite data November 2017-September 2018

Remote Heard Island in the southern Indian Ocean is home to the snow-covered Big Ben stratovolcano, which has had confirmed intermittent activity since 1910. The nearest continental landmass, Antarctica, lies over 1,000 km S. Visual confirmation of lava flows on Heard are rare; thermal anomalies and hotspots detected by satellite-based instruments provide the most reliable information about eruptive activity. Thermal alerts reappeared in September 2012 after a four-year hiatus (BGVN 38:01), and have been intermittent since that time. Information comes from instruments on the European Space Agency's (ESA) Sentinel-2 satellite and MODVOLC and MIROVA thermal anomaly data from other satellite instruments. This report reviews evidence for eruptive activity from November 2017 through September 2018.

Satellite observations indicated intermittent hot spots at the summit through 12 December 2017. A few observations in January and February 2018 suggested steam plumes at the summit, but no significant thermal activity. An infrared pixel indicative of renewed thermal activity appeared again on 7 March, and similar observations were made at least twice each month in April and May. Activity increased significantly during June and remained elevated through September 2018 with multiple days of hotspot observations in satellite data each of those months, including images that indicated lava flowing in different directions from Mawson Peak. MODVOLC and MIROVA data also indicated increased thermal activity during June-September 2018.

Activity during October-December 2017. MIROVA thermal anomalies recorded during October 2017 indicated ongoing thermal activity at Heard (figure 32). This was confirmed by Sentinel-2 satellite imagery that revealed hotpots at the summit on ten different days in October (3, 6, 8, 13, 16, 21, 23, 26, 28, and 31), and included images suggesting lava flows descending from the summit in different directions on different days (figure 33).

The MODVOLC thermal alert data showed no further alerts for the year after 22 October 2017, and the MIROVA system anomalies tapered off in mid-November 2017. The Sentinel-2 satellite imagery, however, continued to record intermittent hotspots at and around Mawson Peak, the summit of Big Ben volcano, into December 2017 (figure 34). Hotspots were visible during six days in November (7, 15, 20, 25, 27, and 30) and three days during December (5, 7, and 12).

Activity during January-May 2018. The satellite images during January and February 2018 were indicative of steam plumes at the summit, but distinct thermal signals reappeared on 7 and 12 March 2018 (figure 35). In spite of extensive cloud cover, the Sentinel-2 imagery also captured thermal signals twice each month in April (4 and 14) and May (9 and 14) (figure 36).

Activity during June-September 2018. Thermal signals increased significantly in the satellite data during June 2018. The sizes of the thermal anomalies were bigger, and they were visible at least nine days of the month (3, 5, 8, 10, 15, 18, 23, 25, and 30). Five substantial thermal signals appeared during July (3, 10, 15, 18, and 28); images on 23 June and 3 July distinctly show a lava flow trending NE from the summit (figure 37). MODVOLC thermal alerts appeared in June 2018 on three days (2, 26, and 27) and on four days during July (7, 8, 9, 10) indicating increased activity during this time. The MIROVA thermal signals also showed a substantial increase in early June that peaked in mid-July and remained steady through September 2018 (figure 32).

Six images in August (2, 7, 9, 22, 27, 29) showed evidence of active lava at the summit, and suggested flows both NE and SE from the summit that were long enough to cause multiple hotspots (figure 38). During September and early October 2018 the satellite images continued to show multiple hotspots that indicated flow activity tens of meters SE from the summit multiple days of each month (figure 39).

Information Contacts: Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).

April 2019 (BGVN 44:04) Cite this Report

Thermal hotspots continue during October 2018-March 2019 at the summit and on the upper flanks

Heard Island, in the Southern Indian Ocean, includes the large Big Ben stratovolcano and the smaller, apparently inactive, Mt. Dixon. Because of the island's remoteness, satellites are the primary monitoring tool. Big Ben has been active intermittently since 1910, and was active during October 2017-September 2018 (BGVN 43:10). Activity continued during October 2018-March 2019.

Satellite photos using Sentinel Hub showed hotspots every month between October 2018 and March 2019. Because the area was frequently covered by a heavy cloud layer, most of the hotspot signals were partially obscured. Though thermal anomalies are usually seen at summit vents, on 18 October 2018 an anomaly was present about 300 m down the E flank. Similarly, on 1 January 2019, a weak anomaly beginning about 200 m down the NW flank was about 300 m long (figure 40).

The MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected three hotspots, two in October and one in early November 2018, all of low radiative power. There were no MODVOLC alert pixels during this period.

Information Contacts: Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).

October 2019 (BGVN 44:10) Cite this Report

Ongoing thermal anomalies at the summit crater during April-September 2019

Heard Island, in the Southern Indian Ocean, is about 4,000 km from its closest point to Australia and about 1,500 km from the closest point in Antarctica. Because of the island's remoteness, monitoring is primarily accomplished by satellites. The Big Ben volcano has been active intermittently since 1910, if not before (BGVN 42:10), and thermal anomalies have been observed every month since June 2018 (BGVN 43:10, 44:04). The current reporting period is from April to September 2019.

During April-September 2019, only one thermal anomaly was detected with the MODIS satellite instruments analyzed using the MODVOLC algorithm, and that was on 10 June (2 pixels). The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected a few scattered thermal alerts in late May-early June and three in September; most were between 1-2 km of the summit and of low to moderate power.

The island is usually covered by heavy clouds, obscuring satellite views. However, Sentinel-2 satellite imagery detected cloud-obscured thermal anomalies during the reporting period, most likely due to a persistent lava lake and possibly lava flows (BGVN 41:08).

Information Contacts: Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).

May 2020 (BGVN 45:05) Cite this Report

Eruptive activity including a lava flow during October 2019-April 2020

Heard Island is located on the Kerguelen Plateau in the southern Indian Ocean and contains Big Ben, a snow-covered stratovolcano with intermittent volcanism reported since 1910. Due to its remote location, visual observations are rare; therefore, thermal anomalies and hotspots detected by satellite-based instruments are the primary source of information. This report updates activity from October 2019 to April 2020.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed three prominent periods of strong thermal anomaly activity during this reporting period: late October 2019, December 2019, and the end of April 2020 (figure 41). These thermal anomalies were relatively strong and occurred within 5 km of the summit. Similarly, the MODVOLC algorithm reported a total of six thermal hotspots during 28 October, 1 November 2019, and 26 April 2020.

Six thermal satellite images ranging from late October 2019 to late March showed evidence of active lava at the summit (figure 42). These images show hot material, possibly a lava flow, extending SW from the summit; a hotspot also remained at the summit. Cloud cover was pervasive during the majority of this reporting period, especially in April 2020, though gas-and-steam emissions were visible on 25 April through the clouds.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

November 2020 (BGVN 45:11) Cite this Report

Persistent thermal anomalies in the summit crater from June through October 2020

The remote Heard Island is located in the southern Indian Ocean and contains the Big Ben stratovolcano, which has had intermittent activity since 1910. The island’s activity, characterized by thermal anomalies and occasional lava flows (BGVN 45:05), is primarily monitored by satellite instruments. This report updates activity from May through October 2020 using information from satellite-based instruments.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed frequent thermal activity in early June that continued through July (figure 43). Intermittent, slightly higher-power thermal anomalies were detected in late August through mid-October, the strongest of which occurred in October. Two of these anomalies were also detected in the MODVOLC algorithm on 12 October.

Sentinel-2 thermal satellite imagery showed a single thermal anomaly on 3 May. In comparison to the MIROVA graph, satellite imagery showed a small pulse of strong thermal activity at the summit of Big Ben in June (figure 44). Some of these thermal anomalies were accompanied by gas-and-steam emissions. Persistent strong thermal activity continued through July. Starting on 2 July through at least 17 July two hotspots were visible in satellite imagery: one in the summit crater and one slightly to the NW of the summit (figure 45). Some gas-and-steam emissions were seen rising from the S hotspot in the summit crater. In August the thermal anomalies had decreased in strength and frequency but persisted at the summit through October (figure 45).

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

May 2021 (BGVN 46:05) Cite this Report

Thermal anomalies during November 2020 and January 2021

Heard is a remote island located in the southern Indian Ocean that contains the Big Ben stratovolcano, which has had intermittent activity since 1910. More recent activity since 2012 through October 2020 has been characterized by thermal anomalies in the summit crater and lava flows, primarily identified based on information from satellite data (BGVN 45:11). This report covers similar activity that continued during November 2020 and January 2021.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows a total of three thermal anomalies of varying power during November 2020 (figure 46). Sentinel-2 thermal satellite imagery shows a single thermal anomaly on 9 November 2020 and later, on 11 November two strong thermal anomalies, possibly two lava flows, were observed descending the S and SW flanks (figure 47). These thermal anomalies were also detected by the MIROVA system. Weaker thermal anomalies were observed on 18 and 20 January 2021 in the summit crater. No new thermal activity was detected after November through April 2021 by the MIROVA system.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

February 2022 (BGVN 47:02) Cite this Report

Thermal anomalies and lava flows continue; strong lava flow event during 3-5 January 2022

The remote island of Heard is located in the southern Indian Ocean and contains the Big Ben stratovolcano, which has been intermittently active since 1910. Activity during late November 2020 through January 2021 produced thermal anomalies over the active Mawson Peak and lava flows (BGVN 46:05), which is similar to activity during this reporting period of February 2021 through January 2022. Information primarily comes from satellite data.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows that the thermal activity was relatively low during February through September 2021, with the exception of four low-power anomalies between late May and early June and two stronger anomalies in mid-July (figure 48). Despite the cloudy weather, Sentinel-2 infrared satellite imagery also detected the stronger anomaly at Mawson Peak on 22 July (figure 49). Very weak anomalies were also visible in satellite imagery on 31 August and 22 and 25 September, though they remained stationary and close to the summit (figure 49).

Renewed thermal activity of varying intensities was detected in Sentinel-2 infrared satellite imagery over the summit area and on the NW and W flanks on 4, 11, 14, and 21 November, though weather clouds often prevented clear views of the summit. On 11 November four anomalies just NW of Mawson Peak formed a “v” shape open to the NW, which could indicate a branched lava flow; this increase in thermal activity was also noted in MIROVA data (figure 50). According to the MODVOLC Thermal Algorithm, there was a total of twelve thermal alerts on 15, 20, and 25 November and 15, 24, and 28 December. A strong anomaly was visible on the W flank on 21 November, accompanied by possible gas-and-steam emissions that extended E and SE.

Anomalies continued to be detected through January 2022. A possible lava flow was observed on 4 December on the NW flank, accompanied by gas-and-steam emissions to the SE. A strong gas-and-steam plume occurred on 16 December, extending NE and accompanied by a lava flow. A small possible branched lava flow was visible traveling NW and SW on 26 December, accompanied by a small gas-and-steam emission to the E. This activity was also visible on 31 December. Sometime during 3 and 5 January, a strong lava flow event occurred, descending the SW flank, based on satellite images (figure 50). Clouds obscured views of the summit during a majority of the month, though a small anomaly and gas-and-steam emission drifting N were detected on 20 January. A weaker anomaly was visible on the NW flank on 30 January.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

February 2023 (BGVN 48:02) Cite this Report

Intermittent lava flows and persistent thermal anomalies during February 2022-January 2023

Heard is a remote island located in the southern Indian Ocean and consists of two volcanic structures: Big Ben and the smaller Mt. Dixon. The active Mawson Peak is located within a 5-6 km wide caldera breached to the SW side of Big Ben. Intermittent eruptions have occurred since 1910 and the most recent eruption began in September 2012 and has mainly been characterized by consistent thermal activity and lava flows (BGVN 47:02). Similar events are covered in this report during February 2022 through January 2023 primarily using various satellite data.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed that intermittent low-to-moderate thermal activity occurred during July 2022 through January 2023 (figure 51). Periods of increased thermal activity were recorded during late July through early August, late September through early October, mid-November, and early-to-mid-December. MODIS satellite instruments using the MODVOLC thermal algorithm also detected a total of 34 strong thermal hotspots on 15 March, 1 and 6 April, 29 May, 14, 20, 22, and 23 June, 10 and 12 August, 23 September, 11, 13, 15, and 26 November, 2, 6, and 8 December, and 11, 13, and 23 January 2023. On clear weather days, Sentinel-2 infrared satellite imagery also captured thermal activity at and near the summit of Mawson Peak (figure 52). A persistent thermal anomaly sometimes accompanied by gas-and-steam emissions was captured to the NW of Mawson Peak at a second vent on 4 and 17 February, 3 August, 15, 25 September, 15 October and at Mawson Peak on 4 June.

Stronger thermal anomalies indicative of active lava flows originated from the second NW flank vent and moved W and SW were captured in Sentinel-2 infrared satellite imagery 39 times on 11 and 31 March, 13 April, 3, 10, 13, 15, 18, 20, 25, and 30 May, 2, 12, 14, 17, 22, and 24 June, 2, 9, 17, and 24 July, 1, 6, 11, 13, and 31 August, 20 September, 2, 22, and 25 October, 9, 14, 16, 21, 24, and 26 November, 4 and 21 December, and 23 January; a hotspot was also detected over Mawson Peak, sometimes accompanied by gas-and-steam emissions (figure 53).

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

August 2023 (BGVN 48:08) Cite this Report

Lava flows and thermal activity persist during February-July 2023

Heard, a remote island located in the southern Indian Ocean, consists of two volcanic structures: Big Ben and the smaller Mt. Dixon. The active Mawson Peak is located within a 5-6 km-wide caldera breached to the SW side of Big Ben. Intermittent eruptions have occurred since 1910; the current eruption period began in September 2012, which has mainly been characterized by thermal activity and intermittent lava flows (BGVN 48:02). This report covers continuing effusive and thermal activity during February through July 2023 using satellite data.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed intermittent low-to-moderate thermal activity during February through July 2023 (figure 54). There were short periods of no thermal activity during early and late June. MODIS satellite instruments using the MODVOLC thermal algorithm also detected a total of 34 strong thermal hotspots on 8 and 24 February, 5, 12, 19, 20, and 22 March, 8, 9, 15, 16, 28, and 29 April, 2 and 18 May, 2 and 3 June, and 11, 13, and 15 July. On clear weather days, infrared satellite imagery captured thermal activity to the W of the summit of Mawson Peak (figure 55). Fresh and cooling lava flows were observed on the SW flank in infrared satellite images underneath the active thermal anomalies (figures 55 and 56). This activity was captured at least 12 times in satellite imagery on 12 February, 6, 21, 24, and 31 March, 5, 13, 25, and 30 April, 23 and 25 May, and 17 July.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).