Exogenous Geological Processes and Earth Surface Changes

Exogenous Geological Processes

Exogenous geological processes are processes that change rocks on the Earth's surface. These changes are produced by temperature, humidity, wind, precipitation, streams and rivers, ice, seas, etc.

Three Main Exogenous Geological Processes

• Erosion: The wearing away of rocks due to the action of the wind, water, and ice; it is a combination of weathering and the transportation of these rock particles.
• Transportation: The transporting of eroded materials which are moved by gravity (landslides) or dragged by the wind, water, or ice.
• Sedimentation: The deposition and accumulation of the transported materials (sediments) that occurs in sedimentary basins (a flat zone that receives sediments from higher zones).

Weathering

Weathering is the alteration and fragmentation of rocks by the joint action of the atmosphere, water, and biological organisms.

Two Ways of Weathering

• Physical: When solid rock becomes fragmented by physical processes that do not change its chemical composition.
• Chemical: When minerals in a rock are chemically altered or dissolved.

Soil

When rocks on the Earth’s surface are weathered, they eventually produce soil. Soil formation is a very slow process which can last thousands of years.

Forms of Appearance of Running Water

Non-permanent Streams

There are two types of non-permanent streams:

• Streams without a fixed channel: Resulting water from rain or melting ice; the resulting relief (badlands) has trenches and gullies.
• Streams with a fixed channel (torrents): Short and irregular streams which run down a fixed channel that are found on steep mountain slopes during periods of heavy rain and melting ice.

Three Parts of a Torrent

• Basin: The area where the rainwater is collected; erosion is dominant.
• Channel: The area where sediment is transported downstream; erosion is dominant.
• Alluvial fan: The area where the sediments that have been transported by the water are deposited, forming a fan-shaped foothill.

Continuous Currents of Water

These run along a fixed channel in a valley; they are the permanent streams (small flowing bodies of water) and the rivers (large flowing bodies of water).

Three Parts of a River

Upper course: The part closest to its source that runs down a steep slope and the water flows quickly; there is a lot of erosion and little sedimentation. The river valley is narrow and "V" shaped; it features: rapids, waterfalls, gorges, and canyons.