Geomorphology of Two Seamounts Offshore Ascension Island, South Atlantic Ocean
Ascension Island is an intra-plate volcanic island in the South Atlantic Ocean, located 80 kilometers west of the Mid- Atlantic Ridge (MAR) and 50 kilometers south of the Ascension Fracture zone. The onshore lithologies show a magma chamber evolution from basic to felsic and physical textures sugges...
Main Authors: | , |
---|---|
Other Authors: | |
Format: | Text |
Language: | English |
Published: |
2003
|
Subjects: | |
Online Access: | http://www.dtic.mil/docs/citations/ADA508765 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA508765 |
id |
ftdtic:ADA508765 |
---|---|
record_format |
openpolar |
spelling |
ftdtic:ADA508765 2023-05-15T18:20:58+02:00 Geomorphology of Two Seamounts Offshore Ascension Island, South Atlantic Ocean Faneros, Geoffrey Arnold, Frederick THALES GEOSOLUTIONS (PACIFIC) INC SAN DIEGO CA 2003-09-01 text/html http://www.dtic.mil/docs/citations/ADA508765 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA508765 en eng http://www.dtic.mil/docs/citations/ADA508765 Approved for public release; distribution is unlimited. DTIC Physical and Dynamic Oceanography Seismology *VOLCANO ISLANDS *SOUTH ATLANTIC OCEAN *GEOMORPHOLOGY *SEAMOUNTS *SURVEYS PHYSICAL PROPERTIES HIGH RESOLUTION ROCK GEOLOGY FRACTURE(MECHANICS) TIME DEPOSITS BATHYMETRY EMPLACEMENT EVOLUTION(GENERAL) SLOPE EARTH CRUST PATTERNS NORTH(DIRECTION) TEXTURE SEDIMENTS CHANNELS CHAMBERS PONDS ISLANDS SHORES VOLCANOES EAST(DIRECTION) OFFSHORE LITHOLOGY ASCENSION ISLAND EXPOSURE(GENERAL) OCEAN SURFACE DEBRIS MAGMA REPRINTS SYMPOSIA *ASCENSION ISLAND(SOUTH ATLANTIC) MAR(MID ATLANTIC RIDGE) Text 2003 ftdtic 2016-02-22T22:00:19Z Ascension Island is an intra-plate volcanic island in the South Atlantic Ocean, located 80 kilometers west of the Mid- Atlantic Ridge (MAR) and 50 kilometers south of the Ascension Fracture zone. The onshore lithologies show a magma chamber evolution from basic to felsic and physical textures suggest deposits erupted within the past several hundred years. The subaerial portion of the island accounts for less than 1 % of the volcano's total volume and the 60 kilometer basal diameter lies in 3200 meters water depth. It lies on a 5- to 6- million-year-old portion of the South American Plate, between magnetic anomalies 3 and 4. The volcano emplacement may have caused significant crustal loading. Ascension Island's offshore geology has not been studied in much detail, in part because of its remoteness. During a July 2002 engineering survey, high-resolution data were acquired for portions of the island's eastern slope, which includes two seamounts. These seamounts have significantly different geomorphology. A prominent northwest-trending ridge deepens from the Ascension volcano to the slopes of what was regarded as the northern seamount for the duration of the survey. The seamount rises to within 800 meters of the ocean surface and deepens to 3800 meters. Its basal diameter is approximately 16 kilometers and it is nearly conical in relief. Geomorphic features suggest it is the result of several flank eruptions. Detailed imagery delineates areas of exposed rock, rock debris, channelized deposits, and sediment ponds. Channel systems, probably created by slope failures, emanate near the central portion of the seamount, forming a radial pattern. Steep slopes outline numerous semi-circular terraces, giving the seamount a stepped appearance. These terraces appear to truncate against the northwest trending ridge, suggesting that seamount eruptions postdate a majority of the Ascension eruptions. See also ADM002146. Presented at the Oceans MTS/IEEE Conference (2003) held in San Diego, California on 22-26 September 2003. Published in the Proceedings of the Oceans MTS/IEEE Conference (2003), p39-49, 2003. U.S. Government or Federal Purpose Rights License. The original document contains color images. Text South Atlantic Ocean Defense Technical Information Center: DTIC Technical Reports database Mid-Atlantic Ridge |
institution |
Open Polar |
collection |
Defense Technical Information Center: DTIC Technical Reports database |
op_collection_id |
ftdtic |
language |
English |
topic |
Physical and Dynamic Oceanography Seismology *VOLCANO ISLANDS *SOUTH ATLANTIC OCEAN *GEOMORPHOLOGY *SEAMOUNTS *SURVEYS PHYSICAL PROPERTIES HIGH RESOLUTION ROCK GEOLOGY FRACTURE(MECHANICS) TIME DEPOSITS BATHYMETRY EMPLACEMENT EVOLUTION(GENERAL) SLOPE EARTH CRUST PATTERNS NORTH(DIRECTION) TEXTURE SEDIMENTS CHANNELS CHAMBERS PONDS ISLANDS SHORES VOLCANOES EAST(DIRECTION) OFFSHORE LITHOLOGY ASCENSION ISLAND EXPOSURE(GENERAL) OCEAN SURFACE DEBRIS MAGMA REPRINTS SYMPOSIA *ASCENSION ISLAND(SOUTH ATLANTIC) MAR(MID ATLANTIC RIDGE) |
spellingShingle |
Physical and Dynamic Oceanography Seismology *VOLCANO ISLANDS *SOUTH ATLANTIC OCEAN *GEOMORPHOLOGY *SEAMOUNTS *SURVEYS PHYSICAL PROPERTIES HIGH RESOLUTION ROCK GEOLOGY FRACTURE(MECHANICS) TIME DEPOSITS BATHYMETRY EMPLACEMENT EVOLUTION(GENERAL) SLOPE EARTH CRUST PATTERNS NORTH(DIRECTION) TEXTURE SEDIMENTS CHANNELS CHAMBERS PONDS ISLANDS SHORES VOLCANOES EAST(DIRECTION) OFFSHORE LITHOLOGY ASCENSION ISLAND EXPOSURE(GENERAL) OCEAN SURFACE DEBRIS MAGMA REPRINTS SYMPOSIA *ASCENSION ISLAND(SOUTH ATLANTIC) MAR(MID ATLANTIC RIDGE) Faneros, Geoffrey Arnold, Frederick Geomorphology of Two Seamounts Offshore Ascension Island, South Atlantic Ocean |
topic_facet |
Physical and Dynamic Oceanography Seismology *VOLCANO ISLANDS *SOUTH ATLANTIC OCEAN *GEOMORPHOLOGY *SEAMOUNTS *SURVEYS PHYSICAL PROPERTIES HIGH RESOLUTION ROCK GEOLOGY FRACTURE(MECHANICS) TIME DEPOSITS BATHYMETRY EMPLACEMENT EVOLUTION(GENERAL) SLOPE EARTH CRUST PATTERNS NORTH(DIRECTION) TEXTURE SEDIMENTS CHANNELS CHAMBERS PONDS ISLANDS SHORES VOLCANOES EAST(DIRECTION) OFFSHORE LITHOLOGY ASCENSION ISLAND EXPOSURE(GENERAL) OCEAN SURFACE DEBRIS MAGMA REPRINTS SYMPOSIA *ASCENSION ISLAND(SOUTH ATLANTIC) MAR(MID ATLANTIC RIDGE) |
description |
Ascension Island is an intra-plate volcanic island in the South Atlantic Ocean, located 80 kilometers west of the Mid- Atlantic Ridge (MAR) and 50 kilometers south of the Ascension Fracture zone. The onshore lithologies show a magma chamber evolution from basic to felsic and physical textures suggest deposits erupted within the past several hundred years. The subaerial portion of the island accounts for less than 1 % of the volcano's total volume and the 60 kilometer basal diameter lies in 3200 meters water depth. It lies on a 5- to 6- million-year-old portion of the South American Plate, between magnetic anomalies 3 and 4. The volcano emplacement may have caused significant crustal loading. Ascension Island's offshore geology has not been studied in much detail, in part because of its remoteness. During a July 2002 engineering survey, high-resolution data were acquired for portions of the island's eastern slope, which includes two seamounts. These seamounts have significantly different geomorphology. A prominent northwest-trending ridge deepens from the Ascension volcano to the slopes of what was regarded as the northern seamount for the duration of the survey. The seamount rises to within 800 meters of the ocean surface and deepens to 3800 meters. Its basal diameter is approximately 16 kilometers and it is nearly conical in relief. Geomorphic features suggest it is the result of several flank eruptions. Detailed imagery delineates areas of exposed rock, rock debris, channelized deposits, and sediment ponds. Channel systems, probably created by slope failures, emanate near the central portion of the seamount, forming a radial pattern. Steep slopes outline numerous semi-circular terraces, giving the seamount a stepped appearance. These terraces appear to truncate against the northwest trending ridge, suggesting that seamount eruptions postdate a majority of the Ascension eruptions. See also ADM002146. Presented at the Oceans MTS/IEEE Conference (2003) held in San Diego, California on 22-26 September 2003. Published in the Proceedings of the Oceans MTS/IEEE Conference (2003), p39-49, 2003. U.S. Government or Federal Purpose Rights License. The original document contains color images. |
author2 |
THALES GEOSOLUTIONS (PACIFIC) INC SAN DIEGO CA |
format |
Text |
author |
Faneros, Geoffrey Arnold, Frederick |
author_facet |
Faneros, Geoffrey Arnold, Frederick |
author_sort |
Faneros, Geoffrey |
title |
Geomorphology of Two Seamounts Offshore Ascension Island, South Atlantic Ocean |
title_short |
Geomorphology of Two Seamounts Offshore Ascension Island, South Atlantic Ocean |
title_full |
Geomorphology of Two Seamounts Offshore Ascension Island, South Atlantic Ocean |
title_fullStr |
Geomorphology of Two Seamounts Offshore Ascension Island, South Atlantic Ocean |
title_full_unstemmed |
Geomorphology of Two Seamounts Offshore Ascension Island, South Atlantic Ocean |
title_sort |
geomorphology of two seamounts offshore ascension island, south atlantic ocean |
publishDate |
2003 |
url |
http://www.dtic.mil/docs/citations/ADA508765 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA508765 |
geographic |
Mid-Atlantic Ridge |
geographic_facet |
Mid-Atlantic Ridge |
genre |
South Atlantic Ocean |
genre_facet |
South Atlantic Ocean |
op_source |
DTIC |
op_relation |
http://www.dtic.mil/docs/citations/ADA508765 |
op_rights |
Approved for public release; distribution is unlimited. |
_version_ |
1766199940895211520 |