Geology

Wrangel Island consists of folded, faulted, and metamorphosed volcanic, intrusive, andsedimentary rocks ranging in age from Upper Precambrian to Lower Mesozoic. The Precambrian rocks, which are about 2 km (1.2 mi) thick, consist of Upper Proterozoicsericite and chlorite slate and schist that contain minor amounts of metavolcanic rocks,metaconglomerates, and quartzite. These rocks is intruded by metamorphosed gabbro,diabase, and felsic dikes and sills and granite intrusions. Overlying the Precambrian strata are up to 2.25 km (1.4 mi) of Upper Silurian to Lower Carboniferous consisting of interbeddedsandstone, siltstone, slate, argillite, some conglomerate and rare limestone and dolomite. These strata are overlain by up to 2.15 km (1.34 mi) of Carboniferous to Permian limestone, often composed largely of crinoid plates, that is interbedded with slate, argillite and locally minor amounts of thick breccia, sandstone, and chert. The uppermost stratum consists of 0.7 to 1.5 km (0.4 to 0.9 mi) of Triassic clayey quartzose turbidites interbedded with black slate and siltstone.^[1]

A thin veneer of Cenozoic gravel, sand, clay and mud underlie the coastal plains of Wrangel Island. Late Neogene clay and gravel, which are only a few tens of meters thick, rest upon the eroded surface of the folded and faulted strata that comprise Wrangel Island. InduratedPliocene mud and gravel, which are only a few meters thick, overlie the Late Neogene sediments. Sandy Pleistocene sediments occur as fluvial sediments along rivers and streams and as a very thin and patchy surficial layer of either colluvium or eluvium.^[1]

Fauna and flora

Wrangel Island is a breeding ground for polar bears (having the highest density of dens in the world), seals, walrus, andlemmings. During the summer it is visited by many types ofbirds. Arctic fox also make their home on the island.

Woolly mammoths survived there until 1700 BC, the most recent survival of all known mammoth populations. However, due to limited food supply, they were much smaller in sizethan typical mammoths.^[3] Domestic reindeer were introduced in the 1950s and their numbers are managed at around 1,000 in order to reduce their impact on nesting bird grounds. In 1975 musk ox were also introduced. The population has grown from 20 to about 200 animals. Recently, Arctic Wolf have been spotted on the island; wolves have lived on the island in historical times but previous packs were eradicated to reduce predation on reindeer and musk ox.^[4]

The flora includes 417 species of plants, double that of any other Arctic tundra territory of comparable size and more than any other Arctic island. For these reasons, the island was proclaimed the northernmost World Heritage Site in 2004.

Climate

Wrangel Island has a severe polar climate. The region is blanketed by dry and cold Arctic air masses for most of the year. Warmer and more humid air can reach the island from the south-east during summer. Dry and heated air from Siberia comes to the island periodically.

Winters are prolonged and are characterized by steady frosty weather and high northerly winds. During this period the temperatures usually stay well below freezing for months. In February and March there are frequent snow-storms with wind speeds of 140 km/h (87 mph) or above.

The short summers are cool but comparatively mild as the polar day generally keeps temperatures above 0 °C (32 °F). Some frosts and snowfalls occur, and fog is common. Warmer and drier weather are experienced in the center of the island because the interior's topography encourages foehn winds.

Average relative humidity is about 82%.