Definition: a comparatively thin, typically horizontal layer within a fluid, in which a property of the fluid varies greatly over a relatively short vertical distance
Definition: A mixed forest biome is a forest biome which contains densely packed populations or communities of broadleaf and coniferous trees, strongly limiting light penetration to the forest floor.
Definition: A landform that extends above the surrounding terrain in a limited area. A mountain is generally steeper than a hill, but there is no universally accepted standard definition for the height of a mountain or a hill although a mountain usually has an identifiable summit and a local relief of more than 300m.