Don Joao de Castro Bank

Photo of this volcano
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 38.23°N
  • 26.63°W

  • -13 m
    -43 ft

  • 382070
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

Most Recent Bulletin Report: July 1997 (BGVN 22:07) Citation IconCite this Report


Magnitude 5.5 earthquake and associated seismic swarm

On 27 June 1997 at 0439 a strong earthquake struck the Azores Archipelago. This main shock reached M 5.5 and was felt with maximum intensity of V on the Modified Mercalli Scale at Terceira and São Miguel islands; in the islands of São Jorge, Pico, and Faial, the respective maximum intensities were III/IV, III/IV, and II/III.

The epicenter was in the vicinity of Don João de Castro bank (figure 2), a submarine volcanic structure. An earthquake swarm began the same day. During one month about 2,000 such events were registered at a reference seismic station on São Miguel island. Approximately 45 earthquakes with M >4 were registered at Terceira island. By 12 September about 2,100 earthquakes had occurred but by then the swarm had declined to 1 or 2 small events a day.

Figure (see Caption) Figure 2. Epicenters during part of the seismic swarm at the Don João de Castro bank (Azores Archipelago), 27 June to 2 August 1997. Provided by SIVISA; courtesy of J.L. Gaspar.

In 1720 AD the Don João de Castro Bank produced an eruption with a Volcanic Explosivity Index (VEI) of 3. After four days an ephemeral, 1-km-long island was created. The area was charted in 1941. Seismic swarms in this general region were also noted in 1988 and 1989 (SEAN 13:10 and 14:03).

Information Contacts: Azores Seismological Surveillance System (SIVISA) (Email: sivisa@mail.telepac.pt), coordinated by a) J.L. Gaspar, Azores University Centre of Volcanology, 9500 - Ponta Delgada, Azores, Portugal and b) Luísa Senos, Meteorological Institute, 9500 Ponta Delgada, Azores, Portugal.

The Global Volcanism Program has no Weekly Reports available for Don Joao de Castro Bank.

Bulletin Reports - Index


Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

03/1989 (SEAN 14:03) Seismicity since May 1988 summarized

07/1997 (BGVN 22:07) Magnitude 5.5 earthquake and associated seismic swarm




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


March 1989 (SEAN 14:03) Citation IconCite this Report


Seismicity since May 1988 summarized

[Don João de Castro Bank information only; extracted from a summary of significant seismic activity in the E Azores since May 1988.]

"A small swarm of earthquakes occurred within the volcano Don João de Castro Bank (figure 1, zone 4) 3-5 October. Sixty-two earthquakes were recorded; no harmonic tremor was detected. A felt earthquake occurred in the same area 23 October; it had intensities of MM IV-V on Terceira and MM III-IV on the N coast of Sao Miguel."

Figure (see Caption) Figure 1. Sketch map showing islands in the eastern Azores. Approximate epicenters of the 3-5 October 1988 swarm at the submarine volcano Don Joao de Castro Bank (4) and the 21 November 1988 and 21 January 1989 earthquakes in the Hirondelle Basin (6 and 7) are shown. Courtesy of R. Moore.

Information Contacts: A. Rodrigues da Silva, Consorcio Geotermico de S. Miguel; R. Moore, USGS; National Institute of Meteorology and Geophysics, Portugal.


July 1997 (BGVN 22:07) Citation IconCite this Report


Magnitude 5.5 earthquake and associated seismic swarm

On 27 June 1997 at 0439 a strong earthquake struck the Azores Archipelago. This main shock reached M 5.5 and was felt with maximum intensity of V on the Modified Mercalli Scale at Terceira and São Miguel islands; in the islands of São Jorge, Pico, and Faial, the respective maximum intensities were III/IV, III/IV, and II/III.

The epicenter was in the vicinity of Don João de Castro bank (figure 2), a submarine volcanic structure. An earthquake swarm began the same day. During one month about 2,000 such events were registered at a reference seismic station on São Miguel island. Approximately 45 earthquakes with M >4 were registered at Terceira island. By 12 September about 2,100 earthquakes had occurred but by then the swarm had declined to 1 or 2 small events a day.

Figure (see Caption) Figure 2. Epicenters during part of the seismic swarm at the Don João de Castro bank (Azores Archipelago), 27 June to 2 August 1997. Provided by SIVISA; courtesy of J.L. Gaspar.

In 1720 AD the Don João de Castro Bank produced an eruption with a Volcanic Explosivity Index (VEI) of 3. After four days an ephemeral, 1-km-long island was created. The area was charted in 1941. Seismic swarms in this general region were also noted in 1988 and 1989 (SEAN 13:10 and 14:03).

Information Contacts: Azores Seismological Surveillance System (SIVISA) (Email: sivisa@mail.telepac.pt), coordinated by a) J.L. Gaspar, Azores University Centre of Volcanology, 9500 - Ponta Delgada, Azores, Portugal and b) Luísa Senos, Meteorological Institute, 9500 Ponta Delgada, Azores, Portugal.

Eruptive History


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


Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
[ 1997 Jun 27 ] [ 1997 Jul 16 (?) ± 15 days ] Uncertain 0   NW of Don Joao de Castro Bank
1720 Dec 8 (?) 1720 Dec 26 ± 5 days Confirmed 3 Historical Observations

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.

Photo Gallery


Two unusual-looking flank craters are visible in this side-viewing sonar perspective of the NW flank of Don Joao de Castro Bank in the Azores taken by U.S. Navy submarine NR-1. The two craters are 90 x 45 m wide. The left-hand and younger crater displays a floor consisting of a chilled lava lake with polygonal surface fractures. The right-hand crater is much less distinct because its surface is obscured by tephra deposits. The line at the right is the center track line of the sonar image.

U. S. Navy image courtesy of Rick Wunderman, 2003 (Smithsonian Institution).
See title for photo information.

Smithsonian Sample Collections Database


There are no samples for Don Joao de Castro Bank in the Smithsonian's NMNH Department of Mineral Sciences Rock and Ore collection.

Affiliated Sites