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Understand the landscape

How do mountains form?

Many mountains form when movements of Earth’s tectonic plates lift and deform the crust.

Colliding plates can fold and thicken rock into mountain ranges. Other mountains form through volcanic activity or movement along faults. Weathering and erosion then reshape their slopes.

Illustrated folded terrain; not a depiction of a named mountain range.

What makes a piece of land an island?

An island is an area of land surrounded by water and smaller than a continent.

Islands can lie in oceans, lakes or rivers. They may form through volcanic activity, changes in water levels, sediment buildup or the separation of land from a larger landmass.

Why do rivers flow toward the sea?

Gravity moves river water downhill, and many river systems eventually reach the sea.

Water follows the slope of the land through a drainage basin. Not every river reaches an ocean: some end in inland lakes, wetlands or dry basins where water evaporates or seeps into the ground.