Earth and Moon

Marine erosion

Marine erosion

The coast is the border area between the mainland and the sea. It is constantly subjected to the erosive action of water, so it acquires very different forms, depending on the type of terrain and the activity of waves, tides and sea currents.

It has cliffs and beaches, deltas and estuaries, and, sometimes, it appears trimmed in old flooded valleys. The marine currents take part of the eroded material towards the sea in some places and deposit it, worn out, in others. Thus a cliff forms in one place and a beach in another.

Cliffs and beaches

The cliff coasts are those that end abruptly at the coast line. Below the cliff itself, of steep or vertical slope, are the inflection point, just above the coast line, and the platform gently inclined towards the sea, which can be sandy or ridge or rocky.

The action of waves and sea currents plucks rocky material, accumulates it at the foot of the cliff and forms a reservoir that, at first, is underwater, but can then emerge forming a small beach. The action of the tides is also important, since during a time it introduces water between the rocks, softening them, and during the rest of the day it leaves them outdoors for the atmospheric agents to act. In addition, it provides several levels of wave performance.

The material contributed to the ocean by the rivers and reworked by the erosion of the waves is distributed along the coasts, where they form beaches, or transported by sea current to the continental shelf and the deepest parts of the ocean.

Beaches are the expansion of the balance between marine erosion caused by waves, tides and sea currents and the contributions provided by marine erosion itself from other areas and rivers. The agents of coastal modeling are waves, currents and tides.

Coastal forms

In addition to the relief of the continental shelf itself, the differences in the forms of marine erosion make the coastal forms very varied.

Cabos: They are parts of the coast that enter sharply into the sea.

Gulfs: A gulf is a large penetration of the sea in the coast forming a curve. At each end it usually has a cape.

Bays: A bay is like a gulf of smaller dimensions and, in general, more open.

Ensenadas: This is the name of a bay or a reduced and protected sea inlet.

Coves: A cove is a narrow cove with steep walls.

Albufera: When a bay is turned into a lake, when its union with the rest of the sea is closed by a coastline, an albufera is formed.

Estuaries: It is the area of ​​the mouth of a river in which the erosion of the sea penetrates.

Deltas: The wide area of ​​the mouth of a river where sediments are deposited above the water level. These materials may come from river, marine or both erosion.

Laughs: They are the areas of old river valleys flooded by marine waters. The coast acquires a morphology that can become very steep.

Fjords: It's like a river, except that in this case the valley occupied by the marine waters is of glacial origin. Since glacial valleys are U-shaped, the walls of the fjords are usually very steep or vertical.

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