Global Volcanism Program

The Global Volcanism Program has no activity reports available for Graciosa.

The Global Volcanism Program has no Weekly Reports available for Graciosa.

The Global Volcanism Program has no Bulletin Reports available for Graciosa.

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Cones

Feature Name

Feature Type

Elevation

Latitude

Longitude

Serra Branca

Stratovolcano

Serra das Fontes

Shield volcano

Timao, Pico

Pyroclastic cone

Vulcao Central

Stratovolcano

Basic Data

Volcano Number

Last Known Eruption

Elevation

Latitude
Longitude

382040

1950 BCE

402 m / 1,319 ft

39.02°N
27.97°W

Morphology

Volcano Landform
Composite

Volcano Types
Stratovolcano
Shield
Caldera
Pyroclastic cone(s)
Lava dome(s)

Rock Types

Major
Basalt / Picro-Basalt
Andesite / Basaltic Andesite
Trachyte / Trachydacite

Tectonic Setting

Rift zone
Oceanic crust (< 15 km)

Population

Within 5 km
Within 10 km
Within 30 km
Within 100 km

2,500
5,941
6,153
96,656

Geological Summary

The SE end of Graciosa, the northernmost of the central Azorean islands, contains a 0.9 x 1.6 km caldera with active fumaroles. The SE caldera rim is the high point of the 7 x 12 km island. The caldera has been the source of eruptions producing significant tephra falls, pyroclastic flows, lahars, and lava flows. Fumaroles are present in a volcanic cave inside the caldera, and a submarine fumarole occurs off the NW coast. Scoria cones erupted along several widely spaced NE-SW-trending fissures fed a youthful lava field that forms the NW end of the island. The most recent eruption from Pico Tomao, NW of the caldera, produced a lava flow during the mid-to-late Holocene that reached the eastern coast NW of the village of Praia.

This volcano is located within the Azores, a UNESCO Global Geopark property.

References

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography.

Larrea P, Wijbrans J R, Gale C, Ubide T, Lago M, Franca Z, Widom E, 2014. 40Ar/39Ar constraints on the temporal evolution of Graciosa Island, Azores (Portugal). Bull Volcanol, 76:796. https://doi.org/10.1007/s00445-0140796-8

Mitchell-Thome R C, 1976. Geology of the Middle Atlantic Islands. Berlin: Gebruder Borntraeger, 382 p.

Neumann van Padang M, Richards A F, Machado F, Bravo T, Baker P E, Le Maitre R W, 1967. Atlantic Ocean. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI, 21: 1-128.

Zbyszewski G, Candido de Medeiros A, Veiga Ferreira O da, Torre de Assuncao C, 1972. Geologic map of Ihla Graciosa (Azores). Servicos Geologicos Portugal, 1:25,000 scale map with 31 p text (in Portuguese).

Eruptive History

There is data available for 1 confirmed Holocene eruptive periods.

1950 BCE ± 1400 years Confirmed Eruption

Episode 1 | Eruption

San Tamao

1950 BCE ± 1400 years - Unknown

Evidence from Isotopic: Ar/Ar

List of 3 Events for Episode 1 at San Tamao

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow	Lava flow reached sea
- - - -	- - - -	Cinder Cone

Deformation History

There is no Deformation History data available for Graciosa.

Emission History

There is no Emissions History data available for Graciosa.

Photo Gallery

The south of Graciosa island is seen in this aerial view from the southwest. The village of Luz is at the center of the image. On the right (the southeast end of the island), is the 0.9 x 1.5 km Vulcão Central caldera, which formed between 60,000 and 11,000 years ago; the caldera rim forms the highest point of the 7 x 12 km island. The lava cave Furna Do Enzofre is situated in the southeastern part of the caldera, and exhibits fumarolic activity. Vegetated volcanic cones and part of the approximately 700,000 year old Serra das Fontes complex can be seen in the left of the photo.

Photo by Angrense, 2007 (Wikimedia Commons).

The roughly 7 x 12 km Graciosa island in the Azores archipelago has a 1.2 x 1.9 km caldera at the SE end, shown in this April 2019 Planet Labs satellite image monthly mosaic (N is at the top). The NW area contains scoria cones, many that have undergone flank collapse or rafting during Strombolian eruptions leaving an amphitheater shape, and lava flows. The growth of the island has been disrupted by multiple major flank collapse events through time.

Satellite image courtesy of Planet Labs Inc., 2019 (https://www.planet.com/).

GVP Map Holdings

Maps are not currently available due to technical issues.

Smithsonian Sample Collections Database

There are no samples for Graciosa in the Smithsonian's NMNH Department of Mineral Sciences Rock and Ore collection.

External Sites

Copernicus Browser

The Copernicus Browser replaced the Sentinel Hub Playground browser in 2023, to provide access to Earth observation archives from the Copernicus Data Space Ecosystem, the main distribution platform for data from the EU Copernicus missions.

MIROVA

Middle InfraRed Observation of Volcanic Activity (MIROVA) is a near real time volcanic hot-spot detection system based on the analysis of MODIS (Moderate Resolution Imaging Spectroradiometer) data. In particular, MIROVA uses the Middle InfraRed Radiation (MIR), measured over target volcanoes, in order to detect, locate and measure the heat radiation sourced from volcanic activity.

MODVOLC Thermal Alerts

Using infrared satellite Moderate Resolution Imaging Spectroradiometer (MODIS) data, scientists at the Hawai'i Institute of Geophysics and Planetology, University of Hawai'i, developed an automated system called MODVOLC to map thermal hot-spots in near real time. For each MODIS image, the algorithm automatically scans each 1 km pixel within it to check for high-temperature hot-spots. When one is found the date, time, location, and intensity are recorded. MODIS looks at every square km of the Earth every 48 hours, once during the day and once during the night, and the presence of two MODIS sensors in space allows at least four hot-spot observations every two days. Each day updated global maps are compiled to display the locations of all hot spots detected in the previous 24 hours. There is a drop-down list with volcano names which allow users to 'zoom-in' and examine the distribution of hot-spots at a variety of spatial scales.

WOVOdat
   Single Volcano View
   Temporal Evolution of Unrest
   Side by Side Volcanoes

WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.

GVMID Data on Volcano Monitoring Infrastructure The Global Volcano Monitoring Infrastructure Database GVMID, is aimed at documenting and improving capabilities of volcano monitoring from the ground and space. GVMID should provide a snapshot and baseline view of the techniques and instrumentation that are in place at various volcanoes, which can be use by volcano observatories as reference to setup new monitoring system or improving networks at a specific volcano. These data will allow identification of what monitoring gaps exist, which can be then targeted by remote sensing infrastructure and future instrument deployments.

Volcanic Hazard Maps

The IAVCEI Commission on Volcanic Hazards and Risk has a Volcanic Hazard Maps database designed to serve as a resource for hazard mappers (or other interested parties) to explore how common issues in hazard map development have been addressed at different volcanoes, in different countries, for different hazards, and for different intended audiences. In addition to the comprehensive, searchable Volcanic Hazard Maps Database, this website contains information about diversity of volcanic hazard maps, illustrated using examples from the database. This site is for educational purposes related to volcanic hazard maps. Hazard maps found on this website should not be used for emergency purposes. For the most recent, official hazard map for a particular volcano, please seek out the proper institutional authorities on the matter.

IRIS seismic stations/networks

Incorporated Research Institutions for Seismology (IRIS) Data Services map showing the location of seismic stations from all available networks (permanent or temporary) within a radius of 0.18° (about 20 km at mid-latitudes) from the given location of Graciosa. Users can customize a variety of filters and options in the left panel. Note that if there are no stations are known the map will default to show the entire world with a "No data matched request" error notice.

UNAVCO GPS/GNSS stations

Geodetic Data Services map from UNAVCO showing the location of GPS/GNSS stations from all available networks (permanent or temporary) within a radius of 20 km from the given location of Graciosa. Users can customize the data search based on station or network names, location, and time window. Requires Adobe Flash Player.

DECADE Data

The DECADE portal, still in the developmental stage, serves as an example of the proposed interoperability between The Smithsonian Institution's Global Volcanism Program, the Mapping Gas Emissions (MaGa) Database, and the EarthChem Geochemical Portal. The Deep Earth Carbon Degassing (DECADE) initiative seeks to use new and established technologies to determine accurate global fluxes of volcanic CO₂ to the atmosphere, but installing CO₂ monitoring networks on 20 of the world's 150 most actively degassing volcanoes. The group uses related laboratory-based studies (direct gas sampling and analysis, melt inclusions) to provide new data for direct degassing of deep earth carbon to the atmosphere.

Large Eruptions of Graciosa

Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).

EarthChem

EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).