WelwitschiaLast Updated on 2011-09-17 00:00:00
The Welwitschia (Welwitschia mirabilis) is a gymnosperm relict plant endemic to the Namib Desert. The species aerial architecture consists of a pair of very wide curled and contorted leaves; these persistent structures are as thick as 1.4 millimetres in the adult specimens. Some individual plants are estimated to have lived for over a millennium.
The Welwitschia plant is endemic to the Namib Desert, with a range spanning northwestern Namibia and southwestern Angola. This taxon is limited in distribution to the desert biome along the southwest coast of Africa. This land strip is about 1000 kilometrers long and stretches from the Kuiseb River, immediately south of Walvis Bay in Namibia (latitude 20 to 24°S), to the Nicolau River in Angola (latitude 15 to 16°S).While some outlier populations are found 200 kilometers inland from the Atlantic Ocean, the... More »
Polar bearLast Updated on 2011-09-07 00:00:00
The Polar bear (Ursus maritimus) spends so much of its annual time at sea that the species is classified as a marine mammal; however, it is also commonly acknowledged as the largest terrestrial carnivore.
Species:-------- Ursus maritimus (Phipps, 1774)
There are nineteen genetically indistinguishable populations of this species, and they are known to interbreed. They are found in Canada (Manitoba, Newfoundland, Labrador, Nunavut, Northwest Territories, Quebec, Yukon Territory, Ontario), Greenland/Denmark, Norway (including Svalbard), Russian... More »
Abbot Ice Shelf, AntarcticaLast Updated on 2011-05-25 00:00:00
The Abbot Ice Shelf is a is a thick slab of ice, attached to West Antarctica's central coast and extending out over the ocean as a seaward extension of the grounded Antarctic Ice Sheet. This ice shelf is one of 47 named Antarctic Ice Shelves.
The Abbott Ice Shelf occurs at the junction of the Bellingshausen and Amundsen Seas. This ice shelf extends an east-west distance of about 250 to 400 kilometers (km) and exhibits a characteristic width of 65 km; this ice shelf is supported by several islands, most significantly, Thurston Island, which provide inherent structural integrity to the Abbot Ice Shelf. Conflicting sources attribute various east-west extents of the Abbot Ice Shelf, from values of 250 to 400 km, presumably due to the definition of the eastern limit.
USGS Geographic Names Information Service
According to the USGS, the Abbot Ice Shelf is 400 km long... More »
Ice sheetLast Updated on 2010-05-08 00:00:00
An ice sheet is the contiguous assemblage of glaciers of sizeable extent; there are presently a number of well defined ice sheets, the two largest being the Antarctic Ice Sheet and the Greenland Ice Sheet. Sheets of less than 50,000 square kilometers in extent are often called ice fields.
Some of the signicificant extant ice fields are the Northern Patagonian Ice Field and Southern Patagonian Ice Field of South America along with the Tierra del Fuego Cordillera of that continent. Other major ice fields are found in Canada, Alaska, Norway and New Zealand.
The occurrence of significant areas of ice sheeting are associated with long term climatic periods called Ice ages.
Extremely large ice sheets are often called continental ice sheets; presently only the Greenland and Antarctic expanses qualify for this term.
The geometry of an ice field is comprised of dozens to... More »
Rainforest Division (Bailey)Last Updated on 2010-02-21 21:47:09Between the equator and lat. 10 N. lies a region classified as wet equatorial or rainforest climate. Average annual temperatures are close to 80°F (27°C); seasonal variation is virtually imperceptible. Rainfall is heavy throughout the year, but monthly averages vary considerably due to seasonal shifts in the equatorial convergence zone and a consequent variation in air mass characteristics. Trewartha classifies this climate as Ar, with no month averaging less than 2.4 in (60 mm) of rainfall.The equatorial region has a rainforest or selva type of vegetation unsurpassed in number of species and luxuriance of tree growth. Broadleaf trees reach 100 to 150 ft (30 to 45 m) in height, forming a dense leaf canopy through which little sunlight reaches the ground. Giant lianas (woody vines) hang from trees. The forest is evergreen, but individual species have various leaf-shedding cycles.The... More »
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