Tarawa

HYDROGEOLOGY OF TARAWA ATOLL, KIRIBATI by G. Jacobson & F.J. Taylor, 1981…

GEOLOGY
Tarawa is a coral atoll formed on top of a volcanic seamount which rises steeply from 4000 m of water. The atoll is roughly triangular in plan and comprises a chain of small islands on the south and northeast sides which partially enclose a central lagoon (Fig. 2). The islands are generally 2-3 m above present sea level. The surface material of most of the islands is coral sand. In places, cemented coral hardpan forms a terrace 1.5-2 m above sea level. The first four bores drilled on Bonriki and Buariki intersected coral sand to depths of 7.5-11.5 m below the ground surface (Appendix 1). Beneath the sand, these bores intersected buried coral reef, 1.5-12.0 m thick. Beneath the buried coral reef, some of the bores encountered interbedded limestone and sand; others had a limestone sequence extending to 30 m below surface, the maximum depth of drilling. The total thickness of the limestone sequence is unknown. ^The nearest atoll to Tarawa that has previously been drilled is Funafuti in the Ellice Islands (Fig. 1), where volcanic basement was not encountered even at 330 m. The nearest atoll where basement has been intersected is Enewetok in the Marshall Islands, where basalt was encountered beneath 1300 m of limestone.

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Tarawa was 2-3 m above sea level in 1981… What is it today? “Highest elevation 3 m (10 ft)”

What was the elevation when the U.S. Marine Corps landed in 1943?

Intelligence reports from Betio were sobering. The island, devoid of natural defilade positions and narrow enough to limit maneuver room, favored the defenders. Betio was less than three miles long, no broader than 800 yards at its widest point and contained no natural elevation higher than 10 feet above sea level. “Every place on the island can be covered by direct rifle and machine gun fire.” observed Edson.

Betio, Tarawa Atoll 1943

Betio, Tarawa Atoll today

http://ontheworldmap.com/kiribati/betio-map.html

km²