dating of marine isotope stage (MIS) 5e, 5c, and 5a coral from
Barbados – implications for palaeo sea-level changes in the
Caribbean. Quaternary International, 120, 41–50.
Stearns, H. T., 1945. Eustatic shorelines in the Pacific. Geological
Society of America Bulletin, 56, 1071–1078.
Stoddart, D. R., 1969. Geomorphology of Solomon Islands coral
reefs. Philosophical Transactions of Royal Society of London,
Series B, 255, 383–402.
Sugihara, K., Nakamori, T., Iryu, Y., Sasaki, K., and Blanchon, P.,
2003. Holocene sea-level change and tectonic uplift deduced
from raised reef terraces, Kikai-jima, Ryukyu Islands, Japan.
Sedimentary Geology, 159, 5–25.
Suzuki, A., Yokoyama, Y., Kan, H, Minoshima, K., Matsuzaki, H.,
Hamanaka, N., and Kawahata, H., 2008. Identification of 1771
Meiwa tsunami deposits using a combination of radiocarbon dating and isotope microprofiling of emerged massive Porites boulders. Quaternary Geochronology, 3, 226–234.
Taylor, F. W., Edwards, R. L., and Wasserburg, G. J., 1990. Seismic
recurrence intervals and timing of a seismic subduction inferred
from emerged corals and reefs of the central Vanuatu (New Hebrides) frontal arc. Journal of Geophysical Research, 95(B1),
393–408.
Taylor, F. W., Frohlich, C., Lecolle, J., and Strecker, M., 1987. Analysis of partially emerged corals and reef terraces in the central
Vanuatu arc: comparison of contemporary coseismic and
nonseismic with Quaternary vertical movements. Journal of
Geophysical Research, 92(B6), 4905–4933.
Taylor, F. W., Isacks, B. L., Jouannic, C., Bloom, A. L., and
Dubois, J., 1980. Coseismic and Quaternary vertical tectonic
movements, Santo and Malekula islands, New Hebrides island
arc. Journal of Geophysical Research, 85, 5367–5381.
Taylor, F. W., Mann, P., Bevis, M. G., Edwards, R. L., Cheng, H.,
Cutler, K. B., Gray S. C., Burr, G. S., Beck, J. W., Phillips,
D. A., Cabioch, G., and Recy, J., 2005. Rapid forearc uplift
and subsidence caused by impinging bathymetric features:
examples from the New Hebrides and Solomon arcs. Tectonics,
24, TC6005.
Veeh, H. H., and Chappell, J., 1970. Astronomical theory of climatic
change: support from New Guinea. Science, 167, 862–865.
Cross-references
Barbados
Density and Porosity: Influence on Reef Accretion Rates
Earthquakes and Emergence or Submergence of Coral Reefs
Glacial Control Hypothesis
Glacio-Hydro Isostasy
Huon Peninsula, P.N.G.
Indonesian Reefs
Last Glacial Interstadials
Last Glacial Lowstand and Shelf Exposure
Last Interglacial and Reef Development
Makatea
Megablocks
Microatoll
Mid Holocene
Pacific Coral Reefs: An Introduction
Radiocarbon (
14 C): Dating and Corals
Red Sea and Gulf of Aqaba
Ryukyu Islands
Sea Level Change and Its Effect on Reef Growth
Sea-level Indicators
Tsunami
Uranium Series Dating
Vanuatu
Volcanic Loading and Isostasy
ENEWETAK ATOLL, MARSHALL ISLANDS
James E. Maragos
U.S. Fish and Wildlife Service, Honolulu, HI, USA
Introduction
The Marshall Islands consist of 29 atolls and 5 isolated
reef islands in the northwest central Pacific Ocean. The
archipelago contains the largest and perhaps oldest atolls
in the world based on the findings of deep drilling surveys
at Enewetak (formerly called Eniwetok) and Bikini
(Figure 1) and the archipelago’s location near the oldest
part of the Pacific Plate. Enewetak Atoll (11
30
0 N,
162
15
0 E) (Figure 2) is located in the northwest corner of
the Republic of the Marshall Islands, and is the second
largest atoll in the Marshall Islands in terms of combined
lagoon, reef, and land area (1,027 km
2
). Enewetak Atoll
and neighboring Bikini Atoll collectively served as the
major American proving ground for nuclear weapons testing after World War II that led to the most comprehensive
scientific and engineering studies of deep ocean atolls in
the world. Enewetak is part of the arid northern Marshall
Islands where vegetation, groundwater, and rainfall (1,470
mm/year) are less compared to those characterizing the central and southern Marshall Islands. However, rainfall can be
highly variable ranging from 605 to 2,422 mm per year. Surface ocean water temperatures normally range from 25
C to
29
C per year. The collective land area of the atoll is 5.8
km
2 with many larger islets concentrated on the eastern half
and only smaller ones on the southwest quadrant of the
atoll. The atoll supported 41 low coral islets mostly along
the perimeter reef, until one on the northern rim (Elugelap)
was first drilled and then completely destroyed and the other
two (Sanil and Teiter) partially destroyed during the “Mike”
hydrogen bomb test of 1952.
Physical characteristics
The Enewetak perimeter reef shows a circumference of 122
km, and three large passes cut through the perimeter reef
connecting the ocean to the lagoon. These occur along the
southeast (1.5 km wide, 55 m depth), south (9.5 km wide,
10–20 m deep), and southwest (6 km wide, 2–4 m deep)
parts of the perimeter reef. All show strong reversing currents during ebb and flood tides. The prevailing northeast
trade winds generate wind waves that break on windward
reefs and, via wave set-up, continually drive water across
the perimeter reefs and into the northeastern lagoon regardless of the state of the tide. These cooler waters then sink
toward the bottom of the lagoon, and warmer excess waters
are eventually discharged through the three passes and over
leeward SW reef crests. The large lagoon can be subdivided
into four sectors depending on the degree of trade-wind
fetch: the leeward lagoon in the northeast quadrant, the
windward lagoon in the southwest quadrant, and the two
transitional lagoon areas at the northwest and southeast
quadrants.
380
ENEWETAK ATOLL, MARSHALL ISLANDS
Barbados – implications for palaeo sea-level changes in the
Caribbean. Quaternary International, 120, 41–50.
Stearns, H. T., 1945. Eustatic shorelines in the Pacific. Geological
Society of America Bulletin, 56, 1071–1078.
Stoddart, D. R., 1969. Geomorphology of Solomon Islands coral
reefs. Philosophical Transactions of Royal Society of London,
Series B, 255, 383–402.
Sugihara, K., Nakamori, T., Iryu, Y., Sasaki, K., and Blanchon, P.,
2003. Holocene sea-level change and tectonic uplift deduced
from raised reef terraces, Kikai-jima, Ryukyu Islands, Japan.
Sedimentary Geology, 159, 5–25.
Suzuki, A., Yokoyama, Y., Kan, H, Minoshima, K., Matsuzaki, H.,
Hamanaka, N., and Kawahata, H., 2008. Identification of 1771
Meiwa tsunami deposits using a combination of radiocarbon dating and isotope microprofiling of emerged massive Porites boulders. Quaternary Geochronology, 3, 226–234.
Taylor, F. W., Edwards, R. L., and Wasserburg, G. J., 1990. Seismic
recurrence intervals and timing of a seismic subduction inferred
from emerged corals and reefs of the central Vanuatu (New Hebrides) frontal arc. Journal of Geophysical Research, 95(B1),
393–408.
Taylor, F. W., Frohlich, C., Lecolle, J., and Strecker, M., 1987. Analysis of partially emerged corals and reef terraces in the central
Vanuatu arc: comparison of contemporary coseismic and
nonseismic with Quaternary vertical movements. Journal of
Geophysical Research, 92(B6), 4905–4933.
Taylor, F. W., Isacks, B. L., Jouannic, C., Bloom, A. L., and
Dubois, J., 1980. Coseismic and Quaternary vertical tectonic
movements, Santo and Malekula islands, New Hebrides island
arc. Journal of Geophysical Research, 85, 5367–5381.
Taylor, F. W., Mann, P., Bevis, M. G., Edwards, R. L., Cheng, H.,
Cutler, K. B., Gray S. C., Burr, G. S., Beck, J. W., Phillips,
D. A., Cabioch, G., and Recy, J., 2005. Rapid forearc uplift
and subsidence caused by impinging bathymetric features:
examples from the New Hebrides and Solomon arcs. Tectonics,
24, TC6005.
Veeh, H. H., and Chappell, J., 1970. Astronomical theory of climatic
change: support from New Guinea. Science, 167, 862–865.
Cross-references
Barbados
Density and Porosity: Influence on Reef Accretion Rates
Earthquakes and Emergence or Submergence of Coral Reefs
Glacial Control Hypothesis
Glacio-Hydro Isostasy
Huon Peninsula, P.N.G.
Indonesian Reefs
Last Glacial Interstadials
Last Glacial Lowstand and Shelf Exposure
Last Interglacial and Reef Development
Makatea
Megablocks
Microatoll
Mid Holocene
Pacific Coral Reefs: An Introduction
Radiocarbon (
14 C): Dating and Corals
Red Sea and Gulf of Aqaba
Ryukyu Islands
Sea Level Change and Its Effect on Reef Growth
Sea-level Indicators
Tsunami
Uranium Series Dating
Vanuatu
Volcanic Loading and Isostasy
ENEWETAK ATOLL, MARSHALL ISLANDS
James E. Maragos
U.S. Fish and Wildlife Service, Honolulu, HI, USA
Introduction
The Marshall Islands consist of 29 atolls and 5 isolated
reef islands in the northwest central Pacific Ocean. The
archipelago contains the largest and perhaps oldest atolls
in the world based on the findings of deep drilling surveys
at Enewetak (formerly called Eniwetok) and Bikini
(Figure 1) and the archipelago’s location near the oldest
part of the Pacific Plate. Enewetak Atoll (11
30
0 N,
162
15
0 E) (Figure 2) is located in the northwest corner of
the Republic of the Marshall Islands, and is the second
largest atoll in the Marshall Islands in terms of combined
lagoon, reef, and land area (1,027 km
2
). Enewetak Atoll
and neighboring Bikini Atoll collectively served as the
major American proving ground for nuclear weapons testing after World War II that led to the most comprehensive
scientific and engineering studies of deep ocean atolls in
the world. Enewetak is part of the arid northern Marshall
Islands where vegetation, groundwater, and rainfall (1,470
mm/year) are less compared to those characterizing the central and southern Marshall Islands. However, rainfall can be
highly variable ranging from 605 to 2,422 mm per year. Surface ocean water temperatures normally range from 25
C to
29
C per year. The collective land area of the atoll is 5.8
km
2 with many larger islets concentrated on the eastern half
and only smaller ones on the southwest quadrant of the
atoll. The atoll supported 41 low coral islets mostly along
the perimeter reef, until one on the northern rim (Elugelap)
was first drilled and then completely destroyed and the other
two (Sanil and Teiter) partially destroyed during the “Mike”
hydrogen bomb test of 1952.
Physical characteristics
The Enewetak perimeter reef shows a circumference of 122
km, and three large passes cut through the perimeter reef
connecting the ocean to the lagoon. These occur along the
southeast (1.5 km wide, 55 m depth), south (9.5 km wide,
10–20 m deep), and southwest (6 km wide, 2–4 m deep)
parts of the perimeter reef. All show strong reversing currents during ebb and flood tides. The prevailing northeast
trade winds generate wind waves that break on windward
reefs and, via wave set-up, continually drive water across
the perimeter reefs and into the northeastern lagoon regardless of the state of the tide. These cooler waters then sink
toward the bottom of the lagoon, and warmer excess waters
are eventually discharged through the three passes and over
leeward SW reef crests. The large lagoon can be subdivided
into four sectors depending on the degree of trade-wind
fetch: the leeward lagoon in the northeast quadrant, the
windward lagoon in the southwest quadrant, and the two
transitional lagoon areas at the northwest and southeast
quadrants.
380
ENEWETAK ATOLL, MARSHALL ISLANDS