Pohnpei
- Landsat 7
- Path 091 Row 055
- 15 May 2000
Pohnpei is the largest single island in the entire Caroline Islands group at 334 km² in area — slightly larger than the island of Babeldaob (331 km²) in Palau, the next largest. The island is home to Palikir, the federal capital of the Federated States of Micronesia.
Pohnpei is located in the Eastern Carolines, near the centre of Pohnpei State, 529 km northwest from Kosrae and 670 km east from Chuuk. Pohnpei is the largest member of the Senyavin Islands group, which also includes the nearby atolls of Ahnd, 8 km to the southwest, and Pakin, 29 km to the northwest. Pohnpei State also includes the atolls of Kapingamarangi, Mokil, Nukuoro, Oroluk, Pingelap and Sapwuahfik as well as the largely submerged Minto Reef.
The island is the highly eroded, dome-like remnant of an ancient shield volcano that was formed by a series of volcanic episodes occurring sporadically between 8 million and 11 million years ago. After an initial shield-forming phase and its subsequent erosion (the island perhaps may have originally reached over 2,000 m in height) a catastrophic landslide event is thought to have destroyed much of the northwestern section of the island before a second phase of volcanic activity covered the southern sections of the island in thick lava flows. The same period of volcanism that gave rise to Pohnpei is likely to have also formed the islands that eventually gave rise to the nearby atolls of Ahnd and Pakin. With the cessation of volcanic activity, Pohnpei has since been shaped over the last million years or so by wind, rain, subsidence, changing sea levels and coral reef growth into its present form.
Pohnpei, 26 km by 22 km, is roughly circular in outline with a coastline that is highly indented by numerous bays and inlets. Surrounding the entire island is a barrier reef that forms a pentagonal-shaped perimeter to the island; the outer edge of the barrier reef typically lies at a distance of 3-5 km from shore, although this can decrease to less than 1 km in the southeast and increase to 10 km in the north. The barrier reef encloses an extensive lagoon with many patch reefs and small islands. The largest of these minor islands include: Deketik, Parempe, Lenger, Sapwtik, Mwahnd Peidi and Mwahnd Peidak in the north; and Pweliko, Takaieu-Dehpehk and Temwen on the east. The barrier reef itself contains a number of low-lying islets, particularly its southern sections.
Pohnpei's mountainous interior contains the highest peaks to be found in the Caroline Islands, rising to 798 m above sea level at the summit of Nahna Laud and to 791 m at Ngihneni, both rising from near the centre of the island (note that there seems to be some confusion over the actual heights of these peaks). In all, there are eleven peaks that reach over 600 m in elevation. From the elevated interior, the land slopes steeply to the coast meeting the lagoon shore in extensive areas of mangrove forest and freshwater swamp forest. There are relatively few low-lying coastal areas on the island.
Vegetation cover on the island is varied and includes crop lands, freshwater swamps, mangrove forest, open grasslands with herbaceous shrubs and small trees, thickets of disturbed native forest and montane rainforests that spread over much of the island from around the 100 m contour to all but the highest and steepest of slopes. Above the rainforest are found the mosses, tree ferns, Kotop palms and stunted rainforest species of the cloud-forest zone of the central highlands. The low-lying islets of Pohnpei's barrier reef are vegetated with atoll forest species.
Climate on Pohnpei is dominated by proximity to the equator and by the Intertropical Convergence Zone — a low pressure belt formed by the vertical ascent of warm, moist air from low latitude regions either side of the equator; heavy annual rainfall and uniform temperatures are thus produced. Although rainfall is heavy year-round, there are pronounced wet and dry seasons with January and February being the driest months. Precipitation levels are strongly affected by topography — ranging from over 3,600 mm on the coast to over 9,000 mm in the central highlands, making Pohnpei one of the Earth's wettest places.
Synonyms: Ponape
image: millenium coral reefs landsat archive/usf millenium global coral reef mapping project/nasa seawifs/nasa jsc
