Earth's Geological Processes and Surface Relief Forms

Surface Relief and Crust Composition

The highlight of geomorphology is the appearance of the outside surface of the Earth. Descriptive forms of relief include mountains, hills, canyons, plateaus, and terraces.

Interpretative Relief Forms

Interpretative forms include witness hills and human-induced modeling. The terrestrial relief consists of two main types of crust:

• Oceanic Crust: Mainly composed of basalt, it forms the ocean basins and is covered with water.
• Continental Crust: Formed by granite and metamorphic rocks, it is thicker and less dense than the oceanic crust, forming the continents.

Geological Agents and Processes

Weathering is the disintegration of rocks due to geological agents that can alter mineral fractures. There are three types: mechanical, chemical, and biological.

• Erosion: The evacuation of geological materials by agents.
• Transportation: The removal of materials by geological agents.
• Sedimentation: The accumulation of material in depressed areas of the surface.

Sedimentary basins are large areas of land subsidence or sinking where material accumulates.

Sedimentary Environments

• Continental: Rivers, torrents, glaciers, wind, and karstic systems.
• Marine: Coastal reefs, continental shelves, slopes, and continental deep-sea basins.
• Transitional: Beaches, deltas, and estuaries.

Geomorphology: Rivers and Wind

Rivers create V-shaped valleys, flat-bottomed valleys, witness hills, peneplains, and terraces. Other features include brooks, streams, canyons, and ramblas.

The wind carries out two types of erosion:

• Deflation: The wind blows materials away, leaving large and small stones, forming stony deserts.
• Wind Abrasion: Wind loaded with sand polishes the surface of rocks.

The Rock Cycle and Plate Tectonics

In the rock cycle, weathering and transformation into sediments take place on the surface. Inside the crust, materials are subjected to high pressure and temperature, turning sediments back into rocks.

The Lithosphere and Asthenosphere

The lithosphere is the outermost part of the upper mantle, firmly attached to the crust. There are two types:

• Continental Lithosphere: Formed by the continental crust and part of the upper mantle.
• Oceanic Lithosphere: Formed by the oceanic crust and part of the upper mantle.

The asthenosphere is a layer at approximately 100km depth where high temperatures cause rocks to lose much of their rigidity.

Lithospheric Plates and Subduction

Lithospheric plates are fragments of the broken lithosphere that form the continents and ocean floor. They can be continental, oceanic, or mixed. Their movements produce the shifting of continents, ocean expansion, and seismic activity at the edges.

Subduction zones are areas where the oceanic lithosphere bends and sinks into the mantle, leading to its destruction. Subduction involves the formation of convective currents driven by the descent of the oceanic lithosphere.