Key Points

A landform is a small to medium-sized part of the earth's surface. A landscape is a larger area composed of several related landforms.

Geomorphic agents like running water, groundwater, wind, glaciers, and waves perform erosion and deposition, which constantly shape and modify the earth's surface.

A river system evolves through three stages: Youth (steep gradients, V-shaped valleys), Mature (gentler slopes, wider floodplains), and Old (flat plains, meanders, oxbow lakes).

Running water carves erosional features such as V-shaped valleys, deep gorges, canyons with step-like slopes, and circular depressions on riverbeds called potholes.

Rivers deposit sediment to form alluvial fans at the foot of mountains and deltas where they meet the sea. Floodplains, natural levees, and point bars are formed by deposition along river channels.

In regions with limestone or dolomite rocks, groundwater is the dominant geomorphic agent, creating a unique landscape called Karst topography through solution and deposition.

The solution action of groundwater in limestone areas forms features like sinkholes, larger valley sinks (uvalas), irregular grooved surfaces (lapies), and underground caves.

Inside limestone caves, dripping water deposits calcium carbonate to create stalactites hanging from the ceiling and stalagmites rising from the floor, which can merge to form pillars.

Glaciers erode by plucking and abrasion, creating cirques (armchair-shaped basins), sharp peaks called horns, serrated ridges called arêtes, and wide U-shaped valleys.

As glaciers melt, they deposit unsorted debris called glacial till to form ridges known as moraines. Other depositional features include sinuous ridges called eskers and oval-shaped hills called drumlins.

High, rocky coasts are dominated by erosion, forming cliffs and wave-cut platforms. Low, sedimentary coasts are dominated by deposition, resulting in beaches, bars, and deltas.

Wave action erodes rocky coastlines to form steep sea cliffs, hollowed-out sea caves, and isolated rock pillars known as sea stacks.

Waves and currents deposit sediments to create beaches, sand dunes, and offshore bars. A spit is a ridge of sand connected to land that may enclose a bay, forming a lagoon.

In arid regions, wind is a major agent of erosion through deflation (lifting loose particles) and abrasion (sandblasting), and also creates depositional features.

Wind erosion in deserts creates gently sloping rocky floors called pediments, shallow depressions called deflation hollows, and distinctive mushroom-shaped rocks.

Wind deposits sand to form dunes of various shapes, including crescent-shaped barchans, U-shaped parabolic dunes, long seif dunes, and ridges that are longitudinal or transverse to the wind direction.