Coastal and Karst Landforms

Coastal Landforms

Coastal Dunes

Besides being in the desert, dunes can also form in coastal areas.

Coastal Dynamics

Coastal Erosion

Coastal relief is modeled by the action of waves, tides, and coastal currents. Waves constantly erode rocky shore areas. By hitting the weakest areas, they form caves, which can cause the gradual erosion of rocks. The resistance of rocks to erosion provokes the formation of arches. The remaining areas are gaps and islets. Rocks erode more easily when they are softer, which can lead to the formation of bays.

Coastal Sedimentation

Sand flats are made of material torn from the cliffs by the waves, materials transported by rivers, and shell fragments left by organisms. The larger sediments are deposited at the bottom of the cliff. Smaller sediments, such as ridges, gravel, and sand, can be transported along the coast and form beaches and littoral cords. Beaches form in sheltered areas, protected from the coast. Littoral and coastal currents carry sediments parallel to the coast. When these currents reach a bay, they deposit sediments, forming a spit. If two spits join, they can close off a bay and form a lagoon. Sand can also be deposited at a distance from the coast, forming bars that can emerge during low tide. When a bar connects an island with the mainland, it forms a tombolo.

Karst Landforms

In limestone massifs, groundwater forms characteristic landforms called karst relief. On the surface, rainwater forms small cavities (lenar), grooves, and sinkholes (dolinas), resulting in uneven and irregular surfaces. Through cracks and fissures, surface water enters the rock and forms circular depressions called dolinas. When water enters the interior of the massif, it dissolves the limestone and forms galleries that can extend for many kilometers. When these galleries widen, they form large chambers. When calcite dissolved in water precipitates, it forms hanging structures called stalactites. If the water reaches the ground and calcite accumulates there, stalagmites are formed. When stalactites and stalagmites join, they form columns.

Sedimentary Rocks

Sedimentary rocks are the most abundant rocks on the Earth's surface. They are formed by the accumulation of sediments, which can be solid fragments, remains of living organisms, or substances precipitated from surface or groundwater.

Types of Sedimentary Rocks

Sedimentary rocks are classified into three groups according to the origin of the sediments:

• Detrital Rocks: These rocks originate from the erosion of other rocks and consist of grains or fragments called clasts. They are classified into three groups according to grain size: conglomerates (larger grains), sandstones (intermediate-sized grains), and clays (finest grains).
• Chemical Precipitation Rocks: These rocks are formed when dissolved salts in water precipitate due to changes in environmental conditions. Limestone rocks are formed when calcite precipitates from water. Examples include travertine, stalactites, stalagmites, and calcareous tuffs, which form when calcite is deposited on plant debris. Salt rocks are formed in coastal or inland lagoons when water evaporates and dissolved salts precipitate. The most important and common salt rocks are halite and gypsum.
• Organogenic Rocks: These rocks are formed from the remains of living organisms, such as algae, corals, mollusks, and other organisms.