A doming or small mound on the crest of a lava flow caused by pressure due to the difference in the rate of flow between the cooler crust and the more fluid lava below.
In physical geography, tundra is an area where the tree growth is hindered by low temperatures and short growing seasons. There are two types of tundra: Arctic tundra (which also occurs in Antarctica)
, and alpine tundra. In tundra, the vegetation is composed of dwarf shrubs, sedges and grasses, mosses, and lichens. Scattered trees grow in some tundra. The ecotone (or ecological boundary region) between the tundra and the forest is known as the tree line or timberline.
High latitude biome dominated by a few species of dwarf shrubs, a few grasses, sedges, lichens, and mosses. Productivity is low in this biome because of the extremes of climate.
Treeless plains that lie poleward of the tree line. (Also called arctic desert.) The plants thereon are sedges, mosses, lichens, and a few small shrubs. Tundra is mostly underlaid by permafrost, with
the result that drainage is bad and the soil may be saturated for long periods. It does not have a permanent snow-ice cover.