Geologic Timescale

Ocean Basin

The features of continental landscapes are mirrored by similar features on the ocean basins. Plateaus, plains, valleys, rolling hills, and volcanic cones and mountains are found beneath the waters of the oceans, just as they are on dry land.


The topography or surface area of the world's continents varies greatly, with features ranging from mountains and other highland areas to plunging canyons and low-lying basins. Despite this diversity of landforms, certain large-scale features are common to all continents.


Plateaus, known variously as tablelands or flat-topped mountains, are regions elevated thousands of feet above their surroundings. They are found on continents around the world, in countries ranging from Algeria to Mexico, from Mongolia to Zimbabwe.

Stream and River

Flowing water, in streams and rivers or across the land in sheets, is the dominant erosional process in shaping Earth's landscape. Streams and rivers are not merely systems for moving surface water to the world's oceans and seas.


Valleys are one of the most common landforms on the surface of the planet. They are carved by flowing water or flowing ice through the process of erosion, which is the gradual wearing away of Earth surfaces through the action of wind and water.


Volcanoes are landforms whose shapes may remain unchanged for centuries or may change drastically in minutes. Some exist singly, looming over a flat landscape.