Following increased SO₂ emissions in December 2002 and mud ejections during February and early March 2003 (BGVN 28:02), the active vent at White Island continued to emit a small plume of steam and gases through 4 April, but seismic activity was at a very low level. Seismicity remained low through August 2003.

Scientists visited White Island during the week of 5-11 April for routine monitoring. This fieldwork included sampling high-temperature fumaroles, measuring carbon dioxide output, and geodetic surveying. The crater lake had grown in size and flooded the active vent, greatly reducing the emission of a gas plume from the vent and also reducing the seismicity to very low levels. A minor plume of steam and gases persisted through 20 June, but was not visible the week of 21-27 June; no further mention of a plume was made in reports through August.

Scientists from the Institute of Geological & Nuclear Sciences (IGNS) who visited the island during the week of 28 June-4 July noted striking changes in the crater lake, which had turned a light green color, and was very warm (58°C). The water level had risen several meters, to ~30 m below the crater rim, flooding all the active vents and spreading into all the areas of the crater floor. This lake is the largest to form within the 1978/90 Crater Complex. Fumarole temperatures ranged from 101 to 114°C.

By the first week of August the lake seemed to be semi-permanent, reaching a size of ~300 m long and somewhat less in width, with an unknown depth. As a result, a Science Alert Bulletin issued by the IGNS on 7 August 2003 noted that the existence of the lake created new hazards. Over the last 10-15 years many small ponds and lakelets have formed in topographic lows or the floors of small sub-craters within the 1978/90 Crater Complex. Their lives have typically been short as they have been filled in by the next eruption, or drained as new vents have formed. The small volumes of these lakes was such that they had no influence on eruptive activity.

However, the current lake volume is large enough that it could influence eruptive activity. Ejection of the lake in an eruption could cause flooding of the shallow stream valleys across the Main Crater floor, maybe as far as the sea. Should there be no significant eruptive activity within the next 18-24 months and the lake continues to fill, it may reach overflow level. In this situation water may overflow into drainage channels on Peg 12 Flat, S of the 1978/90 Crater Complex, and these channels may further erode if water is continuously flowing in them.

As of 29 August seismic and hydrothermal activity remained at the low levels recorded during the past four weeks. The lake level had risen since early July, and the temperature was 53°C, down slightly from 58°C on 2 July. The volcano monitoring team installed temporary benchmarks inside the main crater, so changes in the lake level could be observed from the safety of the crater rim. Although the development of the crater lake has been a concern, there is no significant change in volcanic activity on the island, so the hazard status for White Island remains at Alert Level 1.

Geological Summary. The uninhabited Whakaari/White Island is the 2 x 2.4 km emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes. The SE side of the crater is open at sea level, with the recent activity centered about 1 km from the shore close to the rear crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of volcanism since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. The formation of many new vents during the 19th and 20th centuries caused rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project. Explosive activity in December 2019 took place while tourists were present, resulting in many fatalities. The official government name Whakaari/White Island is a combination of the full Maori name of Te Puia o Whakaari ("The Dramatic Volcano") and White Island (referencing the constant steam plume) given by Captain James Cook in 1769.

Information Contacts: Brad Scott, Institute of Geological & Nuclear Sciences (IGNS), Private Bag 2000, Wairakei, New Zealand (URL: http://www.gns.cri.nz/).