Bays and headlands are two coastal features which are closely related. These features are always established on the same coastline. Bays are water bodies (either fresh water or salt water) which are bordered by land on three sides, and the water regions are referred to as gulfs. Headlands are land bordered by either salt or fresh water on three sides; these lands are referred to as capes. Bays are made up of soft rocks while headlands are made up of hard rocks. Bays are water bodies located on a land next to the sea or a lake located between two headlands. Bays are usually formed where weaker rocks like clay and sand are eroded leaving a band of harder rocks. Bays and headlands are formed where the parallel bands of harder and softer rocks are perpendicular to the coastline.
Characteristics of Headlands and Bays
Bays and headlands usually form on a discordant coastline, where the coastline has bands of rocks with varying resistance which run perpendicular to the coastline. The differing resistance on the coastline to erosion results in the formation of the bays and headlands. Hard rocks like granites can resist the wave which causes erosion resulting in the creation of a peninsula (a raised land mass) while the softer rocks like clay are easily eroded thus creating bays. Headlands are characterized by intense erosion, steep sea cliffs, rocky shores and high breaking waves. Bay has less wind activity and less wave activity than the regions with water outside the bay.
Formation of Bays and Headlands
Headland features are formed on various harsh coastlines with bands of rock which have an alternating resistance which runs perpendicular to the coastline. Headlands are usually formed when the ocean attacks a part of the coastline with alternating bands of soft and hard rocks. Soft rock bands like clay and sand tend to erode faster than resistant rocks like chalk. This will leave part of the land protruding out into the ocean, and this land is referred to as a headland, and the region where the band of soft rocks has been eroded away from right next to the protruding headland is referred to as a bay. The process of erosion which occurs during this formation includes hydraulic action, attrition, and various types of weathering. Continuous attacking of the materials and waves from the ocean on the cliff will cause soft rock erosion, thus leaving some parts of the land protruding. The bay forms in places where less resistant rocks or soft rocks like clay and sands have eroded leaving a band of more resistant rocks like granite, limestone, and chalk where headlands form. Wave refraction, which occurs on the headland, concentrates wave energy on the land, and this leads to the creation of stacks, natural arches, and caves.
Rock Formations on Headlands
During the formation of a sea cliff, wave erosion weakens the unique slopes of the coastline which then retreats towards the land. This tends to accelerate the shear stress on the cliff-forming materials while increasing mass movement. The debris which collects at the bottom of the cliff during the landslides is removed by the water wave when there is a strong storm. The debris is deposited in a nearby bay by the longshore current to form the sediment. The joints on the headland are usually eroded back to create a cave, which can erode further to create arches.
Caves are formed by erosion and weathering of the band of hard rocks on the already formed headland. The caves form when the waves go through the cracks on the cliff face. The water contains various soft rocks and sand which will grind at the rocks until the initial crack turns into a cave. If a cave is formed on the headland, it might break through to the other side thus creating an arch. The arch will eventually grow bigger until it collapses leaving a stack on one side and the headland on the other. The stack will then be attacked right at the base by the wave, and this will weaken this structure thus collapsing to create a stump.
How Stable Are Headland Bay Beaches?
Beaches are unique geological features which tend to fluctuate between the retreat and advance of the sediments. The fluctuation of the sediments is caused by various natural factors like winds, currents, tides, and waves. Numerous human-made elements like fluid withdrawal and building of dams can also affect the stability of headland bay beaches. Headland bay beaches are usually categorized into three different sedimentation states, including static equilibrium, dynamic equilibrium, and unstable equilibrium.
Static equilibrium refers to a stable beach which never experiences erosion, sediment deposition, or littoral drifts. The waves are diffracted around the headland and also near the beach when it is in a static equilibrium state. The stable beach is made up of stable hard rocks, which cannot be affected by the waves. Therefore no soil or stone is removed when strong waves hit the beach.
Dynamic equilibrium occurs when the sediments on the beaches are eroded and deposited at an equal rate. These beaches are always located near a river which supplies sediments to replace those that have been eroded away, thus maintaining the beach.
Unstable equilibrium refers to an unstable beach, usually caused by human interactions like dammed river or breakwater. The unshaped beaches are usually reshaped by the continuous deposition and erosion on the beach. The continuous deposition and erosion process will continue until a state of stability is reached on the bay. Once it is at static equilibrium, the unstable beaches will stabilize and can no longer be affected by erosion.
Significance of Bays
The wave refraction breaks the wave energy through the bays, and the sheltering effect of the headlands protects the bay from storms. This means that the waves which reach the shores of the bay are weaker than the ones reaching the headland thus creating a perfect condition for various water activities like swimming and surfing.
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