Graciosa

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  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 39.02°N
  • 27.97°W

  • 402 m
    1319 ft

  • 382040
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

The Global Volcanism Program has no activity reports for Graciosa.

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

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

Basic Data

Volcano Number

Last Known Eruption

Elevation

Latitude
Longitude
382040

1950 BCE

402 m / 1319 ft

39.02°N
27.97°W

Volcano Types

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

Rock Types

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

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 small 0.9 x 1.6 km caldera with active fumaroles. The 402-m-high SE caldera rim is the high point of the small 4 x 8 km island. The caldera has been the source of eruptions producing significant tephra falls, pyroclastic flows, lahars, and lava flows. An important fumarole field is located in a volcanic cave inside the caldera, and a submarine fumarole occurs off the NW coast of Graciosa. 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.

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 Volc, 76:796. http://dx.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


Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).


Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1950 BCE ± 1400 years Unknown Confirmed   Ar/Ar San Tamao

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

Photo Gallery


The small 4 x 8 km island of Graciosa is seen in this NASA Space Shuttle image with north to the upper left. Cloud banks partially obscure the SE end of the island, which contains a small 0.9 x 1.6 km caldera with active fumaroles. Scoria cones are found over much of the island, and several widely spaced NE-SW-trending fissures fed a youthful lava field that forms the NW end of the island.

NASA Space Shuttle image ISS004-E-10893, 2002 (http://eol.jsc.nasa.gov/).
The Caldeira area of Graciosa is seen in this aerial view from the SW with the village of Luz at the center of the image. The small, 0.9 x 1.6 km caldera at the SE end of the island contains active fumaroles. The 402-m-high SE caldera rim is the high point of the small 4 x 8 km island. The most recent eruption from Pico Tomao, NW of the caldera, produced a lava flow that reached the eastern coast NW of the village of Praia.

Photo by Angrense, 2007 (Wikimedia Commons).

Smithsonian Sample Collections Database


A listing of samples from the Smithsonian collections will be available soon.

Affiliated Sites

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).
WOVOdat 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.
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).
MODVOLC - HIGP MODIS Thermal Alert System 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.
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.