COASTAL LANDFORMS

1. The action of waves, tides and currents

The coastlines are under the constant action of the waxes. Tides and currents are changing on horn day today. On calm days, when winds are slight, winds do little damage to the shoreline. The average pressure of Atlantic waves on the adjacent coast is about 600 lb. per square foot in summer. During the storms, the pressure exceeds more than 6000 lb. or three tones per square foot. Tides may affect marine erosion mainly by an extension line of erosion into a zone of erosion.  A current help to move eroded debris and deposits it as a slit, sand and gravel along the coasts.

2. The mechanism of marine erosion

Waves are the most powerful agents of marine erosion. A normal wave in an open ocean may measure 20 feet high and 400 feet long. The crust cruel over and breaks into the shores in a mass form as a breaker. The water that finally rushes up the beach and hurls rock debris against the land is termed a swash. The water is sucked back and retreats as backwash. Another element in offshore drift is the undertow. Marine agents of erosion operate in the following ways to transform the coastal landscape.

• Corrosion: Corrosion refers to the gradual degradation or destruction of materials, especially metals, through chemical or electrochemical reactions with their environment. It is a natural process that occurs over time, often driven by exposure to moisture, oxygen, acids, or other corrosive substances. Corrosion can have detrimental effects on the structural integrity and functionality of materials, leading to economic losses and safety concerns. 
• Attrition:  Attrition, in a general sense, refers to the process of gradually wearing down or diminishing something over time through a variety of mechanisms. The term is commonly used in different contexts, including human resources, geology, and military strategy. 
• Hydraulic action: Hydraulic Action is the sheer force of water crashing against the coastline causing material to be dislodged and carried away by the sea.
• Solvent action: The rate of marine erosion depends on the nature of the rocks, the amount of rock exposed to the sea, the effects of tides and currents, and human interference in coast protection. 

3. Coastal Features of Erosion

• Caps and Bays: Caps are resistant headlands that stand out against softer bays eroded by waves and currents.
• Cliffs and Wave-Cut Platforms: These are classic features of erosion, with cliffs showcasing the impact of waves and the platform revealing the gradual retreat of the coastline.
• Cave, Arch, Stack, and Stump: These features illustrate the progressive erosion of headlands. Caves enlarge, forming arches, which can collapse into stacks, leaving stumps as remnants.
• Geos and Gloups: These are less common features, but fascinating nonetheless. Geos are small caves eroded into the base of cliffs, while gloups are larger, deep depressions with a narrow openings.

Coastal Features of Deposition

• Beaches: Beaches are the most common depositional feature, formed by the accumulation of sand, gravel, and pebbles from eroded cliffs and transported by waves and currents.
• Spits and Bars: These elongated landforms are formed by the deposition of sand and sediment, often connecting islands to the mainland or creating sheltered bays.
• Marine Dunes and Dune Belts: Wind-blown sand from beaches can form dunes, creating coastal landscapes like dune belts and ridges.

Types of Coasts

• Coastal Lines of Submergence: These coasts are formed when land is submerged by rising sea levels, resulting in features like rias, fiords, and Dalmatian coasts.
• Ria Coasts: These have drowned river valleys with elongated inlets and estuaries.
• Fiord Coasts: These are glaciated valleys submerged by the sea, creating deep, narrow inlets with steep cliffs.
• Dalmatian Coasts: These are characterized by elongated, parallel islands and inlets formed from submerged mountain ranges and valleys.
• Estuarine Coasts: These are formed where rivers meet the sea, creating partially enclosed areas with brackish water.
• Coastal Lines of Emergence: These are coasts exposed to a relative fall in sea level, resulting in uplifted land features.
• Uplifted Lowland Coasts: These are former flat areas that have been uplifted and eroded by the sea, creating low cliffs and rocky shores.
• Emergent Upland Coasts: These are former highlands now exposed to falling sea levels, often featuring steep cliffs and rugged landscapes.

3.1. Coastal Lines of Emergence

These are stretches of coastline that have been exposed by a relative fall in sea level. This can happen due to various factors, including:

• Isostatic Rebound: As ice sheets melt, the land underneath rises due to the reduced weight, exposing previously submerged areas. This is particularly evident in Scandinavia and the Hudson Bay region.
• Tectonic Uplift: Plate movements can uplift landmasses, causing the coast to move further out from the sea. For example, the west coast of North America is an emergent coastline due to tectonic activity.
• Eustatic Sea Level Change: Global changes in sea level, such as during glacial periods, can also expose land areas previously covered by water.

Types of Emergent Coastlines

• Uplifted Lowland Coasts: These were formerly flat areas that have been raised above sea level by tectonic or isostatic processes. They often feature low cliffs and rocky shores, with evidence of past marine features like wave-cut platforms and raised beaches.
• Emergent Upland Coasts: These were previously part of the interior landmass but have been exposed to falling sea levels. They often have steep cliffs and rugged landscapes, with features like fjords and sea stacks created by erosion.