Accession Number : AD0768300

Title :   The Geomorphology of Johnston Atoll.

Descriptive Note : Technical rept.,

Corporate Author : NAVAL OCEANOGRAPHIC OFFICE WASHINGTON D C

Personal Author(s) : Ashmore,Stanley A.

Report Date : JUL 1973

Pagination or Media Count : 38

Abstract : Johnston Atoll (16 degrees 44 minutes N., 169 degrees 30 minutes W.) is one of the approximately 400 annualr reef forms that have been given the name atoll. Johnston Atoll, however, differs from most other atolls in having an outer reef that extends around only one quarter of its submarine platform. Two hypotheses have been proposed to account for the apparent incompleteness of Johnston Atoll. Either the atoll has been tilted, or lowered sea levels have allowed a portion of the atoll to be removed. Testing both hypotheses against detailed hydrographic survey data indicates that the sea-level-change hypothesis is the more likely. The sea-level-change hypothesis is supported by the existence of two distinct submarine terraces, one at approximately 5 fathoms, and the other at approximately 10 fathoms. In addition to supporting the sea-level-change hypothesis, the submarine terraces provide potentially valuable evidence for determining times and elevations for former worldwide sea levels. (Author)

Descriptors :   (*JOHNSTON ISLAND, GEOLOGY), CORAL REEFS, TERRAIN

Subject Categories : Geology, Geochemistry and Mineralogy

Distribution Statement : APPROVED FOR PUBLIC RELEASE