Landforms of Erosional Coasts

A landform is a natural or artificial feature of the solid surface of the Earth or other planetary body. The terrain landscape formed due to the landform is topography. The characteristic physical attributes like slope, stratification, elevation, orientation, rock exposure, and soil type categorize landforms. Landform includes hills, mounds, ridges, berms, cliffs, rivers, valleys, volcanoes, peninsulas, and various other structures. Minor landforms include canyons, valleys, basins, and buttes, whereas major landforms are hills, mountains, plateaux, and plains. 

Coastal Landforms Definition

Coastal landforms mean any of the relief features remaining on the coast because of the combination of processes, sediments, and the geology of the coast itself. The development and persistence of landforms are the results of a combination of processes acting on sediments and rocks present on the coast. The power and current of waves play a major role in these processes. 

Beach, delta, coastal dune, wave-cut platform, a sea stack, sea cliff, and sea arch are some of the famous coastal landforms.

Erosional and Depositional Landforms 

There are two major types of coastal landforms - erosion and deposition. The erosional and depositional landforms, though they contain some similar features, show distinct different types of landforms. Erosional landforms show high relief and rugged topography. They can be seen on the leading edge of lithospheric plates, the west coasts of North and South America. The erosional coasts also occur due to glacial activity, which is seen in New England and the Scandinavian countries.

The erosional features are dominated by exposed bedrocks with steep slopes and high elevations near the shore. The bedrocks resist the erosion leading to its slow rate of shoreline retreat. The type of rocks and their lithification play a major role in the rate of erosion.

Features of Sea Erosion  

Seacliff Formation

The sea bedrock cliffs range from a few meters to hundreds of meters above sea level. The sea cliff landforms are the most widespread of erosion coasts. The wave-induced erosion near sea level and collapse of rocks at higher elevation lead to vertical nature. One can observe a notch in cliffs when they are extended to the shoreline where waves batter the bedrock.

At the base of the sea cliffs, one can find many veneers of sediment that form a beach. The sediment might be of sand, but it is more of cobbles or boulders, a coarse material. These types of beaches might get demolished with the strong waves during the stormy seasons as they are made in low wave-energy conditions. Some beaches of California and Oregon are its example. 

Coastal erosion means breaking down and carrying away materials by the sea, and deposition means the material carried away by sea is deposited or left behind on the coast. Coastal erosion happens due to ‘destructive waves’. We know that in the stormy season, the waves are very powerful and can destroy material into pieces. The strong backwash of waves pulls the material away in the sea.

Destructive Waves  

Erodes through four main processes as -

• Hydraulic Action 

It is a force against the coastline that leads to dislodging and carrying the material away by the sea.

• Compression 

This can be seen in rocky areas when the water burst against the crack of rocks. These cracks keep on spreading as the air gets compressed and decompressed because of the waves crashes. The creation of caves is the result of compression as the rocks go on breaking off.

• Abrasion 

Abrasion means when the material is thrown to the coast with the swashes, they tend to break and spread, and this leads to more material backwashing into the sea. 

• Attrition 

Attrition means the crashing of rocks and stones against each other while they are carried away by the sea. The attrition gives result formation of sand and rounded pebbles on the beach. 

• Sea Caves 

When the cracks in the rock at the base are eroded and expanded by the continuous crashing of waves, the sea caves are formed. It is the result of constant compression and hydraulic action.

• Sea Arch 

Sea arch is formed when the headland is broken through while waves continue to erode and expand to cut through.

• Sea Stack 

Sea stack means the sea arch is no more capable of supporting till the root and falls broken in the sea. The remaining pillar-like rock is called a sea stack.

• Sea Stump 

The sea stump means a broken pillar is remaining just above sea level. It is a sea stuck almost completely eroded.

Constructive Waves  

Are of low energy and high swashes. Swashes mean the waves deposit or drop the material on the coast. They have stronger swashes than backwashes. This leads to a build-up of material washed away during backwashes. This results in the formation of beaches.