Wind, Coastal, Glacial, and Karst Landform Modeling
Wind Modeling
Wind Action: Wind is the primary agent shaping landscapes in hot deserts. In these areas, wind carries out two main erosion processes:
- Deflation: Wind carries away smaller materials, leaving behind larger ones, resulting in a rocky desert known as a reg.
- Abrasion: Wind laden with sand polishes rock surfaces.
Wind Transport and Sedimentation: Wind carries large volumes of fine materials over enormous distances. Fine sand and dust are carried high into the troposphere, where they can remain suspended for weeks or months. Types of wind sedimentation include:
- Loess Deposits: Accumulations of dust transported by wind, covering large areas in regions peripheral to deserts.
- Dunes: Accumulations of sand that can be crescent-shaped, presenting a ridgeline, or form parallel to the wind direction, developing a sinuous ridge.
Coastal Modeling
Coastal Water Action: Two main erosion processes occur:
- Cliff Retreat: Waves impact the base of cliffs, causing the cliff to collapse and retreat. This process creates a surface that may be partially exposed during low tide, known as an abrasion platform.
- Crushing and Washing of Materials: Blocks and rock fragments are broken down.
Coastal Transport and Sedimentation: Sand is transported along the coast by littoral currents to more sheltered areas, where sediments create:
- Beaches: Accumulations of sand or gravel in areas where the shoreline has a gentle slope.
- Tombolos and Spits: Sandy ridges perpendicular or parallel to the coast, which tend to isolate small lagoons and coastal marshes.
Glaciers
Glacial Action: A glacier, a large mass of ice, flows slowly under its own weight. In the valleys of mountainous regions, glacier tongues form, producing erosive features:
- U-Shaped Valleys: Broad, deep valleys with a rounded profile.
- Overdeepened Areas: Concavities produced by the flow of ice. When the ice melts, these areas form lakes or ponds.
Glacial Transport and Sedimentation: Glacial sedimentation produces tillites, accumulations of clasts. The most frequent are moraines, associated with the movement of glacier tongues.
Karst Modeling
Karst Action: Karst geological processes involve surface and groundwater with the capacity to dissolve rocks. Types of landforms include:
Surface Erosive Forms:
- Dissolution: Rainwater running over soluble rocks creates grooves called karren or lapies.
- Collapse: When the roof of a subterranean cavity collapses, depressions called dolines or sinkholes appear on the surface.
Underground Erosive Forms:
- Roughly horizontal tunnels. When tunnels are very narrow, they are called “gateiras”.
- Furnas: Vertical ducts that sometimes reach the surface.
- Sima: Large cavities of irregular shape.
Karst Sedimentary Forms:
- Accumulation of Decalcification Clay: When calcium carbonate dissolves from limestone, a clay residue remains, which can accumulate in underground cavities.
- Precipitation of Soluble Salts: Dissolved calcium carbonate can precipitate, forming tufa, stalagmites, stalactites, and other formations, often called travertine.