Wind and Coastal Erosion: Landforms and Sedimentation
Wind Erosion and its Effects
For wind erosion to occur, a significant amount of material needs to be dissolved, there must be little vegetation, and low humidity. Wind erosion manifests primarily through two processes:
- Deflation: The wind picks up loose material, ranging from small to medium sizes, and transports it to other locations.
- Wind Abrasion: Thanks to the material transported by deflation, the wind erodes and polishes the surface of rocks.
Methods of Erosion and Resulting Landforms
- Alveoli: Tiny holes produced in the rocks.
- Fungiform Rocks: Aeolian abrasion can create isolated rock masses resembling mushrooms. Most sand grains are moved near the ground, so the lower areas of the rocks are eroded more than the upper parts.
- Desert Pavement: Most of the desert surface is covered by a tapestry of coarse rocks. These are the result of deflation, which has removed the medium and fine-sized materials, leaving behind those it could not move.
Forms of Sedimentation
- Dunes: Sand deposits that were transported by the wind.
- Loess: Deposits of fine-sized materials that have been transported by wind over long distances.
Coastal Erosion and Landforms
Marine waters are subjected to three different types of movement: waves, currents, and tides. These movements contribute to coastal erosion and the formation of various landforms.
Coastal Landforms Caused by Erosion
- Cliff: Characterized by the step that separates the sea from the land surface.
- Abrasion Platform: A horizontal surface located at the foot of the cliff.
- Coves and Promontories: The existence of rocks resistant to marine erosion in the littoral zone favors the formation of coastlines with alternating cliffs and coves.
- Coastal Islets: These are remnants of ancient mounds that have lost connection with the mainland.
- Natural Arches: Hollows or crossings in headlands situated at the front of the cliff. They arise as a result of differential erosion.
- Rasas: Terraces located on the cliff.
Coastal Landforms Caused by Sedimentation
- Beaches: Coastal deposits of sand or gravel which, like other forms of coastal sedimentation, are partially submerged.
- Deltas: Deposits accumulated at the mouth of a river.
- Barrier Islands: Elongated sandy islands that rise parallel to the coast.
- Spits: Bars with one end connected to the coast.
- Tombolos: Deposits connecting an island with the mainland.
- Lagoons: Coastal gaps partially or completely separated from the sea by a bar.
Structural Landforms
Stratification
- Structural Plain: Originates in places where the horizontal strata are arranged in their original position. Hard materials protect the softer ones beneath them, but where erosion manages to penetrate the hard rocks, the soft rocks are quickly eroded.
- Relief on Coasts: This originates in areas with gently inclined stratification. It is an asymmetric relief coinciding with gentle slopes in hard rock layers and abrupt cuts in the soft ones.
- Peaks: If the stratification is vertical, hard coatings originate highlights produced, as in previous cases, by differential erosion.
Folds and Fractures
- Folds: Folds in the form of an “A” are called antiforms, while those U-shaped are synforms.
- Fractures: These are planes of weakness where water enters, favoring weathering.
Davis Cycle Phases
The Davis Cycle, also known as the cycle of erosion, describes the evolution of landforms over time. It consists of three main phases:
- Youth: The topography is very steep, erosion is very intense, and deep valleys form as rivers develop.
- Maturity: The relief is smoothed, erosion is less intense, mountains are rounded, and valleys open.
- Senility or Old Age: The relief is almost completely flat, forming a peneplain, and erosion is almost nonexistent.