Saint Lawrence Island
- Terra MODIS
- 06 July 2001
- 22:55 UTC
The island of Saint Lawrence is located in the northern reaches of the Bering Sea, lying 72 km southeast from the Chukostsk Peninsula of the Russian Far East. With an area of 4,640 km², St. Lawrence measures 162 km from east to west and is up to 37 km across, from north to south.
This tundra-covered and often barren island has two distinct sides. The eastern side of the island forms a low-lying plain that is punctured by several isolated upland regions; the western side is more elevated in nature, where the eastern lowlands rise via an escarpment to a volcanic upland area on the northern side and to a flat plateau in the west that gives way a mountainous region in the southwest.
Much of the eastern two-thirds of St. Lawrence Island consists of a low-relief plain averaging 5 m to 40 m above sea level. The plain contains a profusion of small lakes and streams that are frozen throughout most of the year. The plain is broken by three upland areas: At the extreme eastern end are the Kinipaghulghat Mountains, farther to the west are a series of lower upland areas comprising low, rounded hills with average elevations of between 150 m and 400 m. These areas can be identified in the above image by several light patches of snow midway along the islands' eastern half. A third group of peaks, the Kialegak Mountains, extends a short distance northwards from Southeast Cape — the southernmost point of St. Lawrence Island.
The low plain of the east suddenly rises in a steep-sloped escarpment to one of the most interesting areas on the island — the Kookooligit Mountains, which form a 30 km by 40 km bulge on the northern coast of the island. The escarpment can be seen in the above image as series of snowy bands running in an open-arc near the island's centre. The Kookooligit Mountains, rising to 673 m above sea level at Atuk Mountain, are a large shield volcano structure of Pleistocene-Holocene age. Composed of basalt lava flows, the shield is overlain by an east to west trending line of around 100 small volcanic cones. To the southwest, the Kookooligit Mountains descend to the flat Putgut Plateau (30-70 m elevation) before meeting the Puvoot Mountains.
Coastlines around St Lawrence are generally low and are characterised by the presence of coastal lagoons. Lagoons can be found all along the northern coast (except where the bulge of the Kookooligit Mountains reaches the sea) and are at their most impressive along the southern coast. Premier examples include the large Koozata, Sekinak, Maknik and Kiloknak lagoons; each is separated from the open sea by a thin ribbon of gravel or sand. In the above image the lagoons lining the shore of Powooiliak Bay are particularly prominent — they appear as dark green bodies of water. Cliffs, steep slopes and rocky beaches can be found along the southwestern coasts of the island.
The waters around St Lawrence are generally shallow and receive a flow of water (the Anadyr Current) from the Bering Sea shelf edge that brings cold nutrient rich waters to the area, making the continental shelf in this region biologically productive — phytoplankton blooms are visible around much of the island in the above image — attracting large numbers of birds and sea mammals.
image: MODIS rapid response project at nasa/goddard space flight center
