ENSENADA: CHARACTERISTICS, TRAINING AND EXAMPLES - ENVIRONMENT - 2025

A cove is an oval or circular landform with a narrow entrance. In general they are small in size and can be present on the shores of oceans, rivers and lakes.

The inlets are formed on concordant coasts, which present a layer of material very resistant to erosion facing the sea and internally layers of softer rocks.

Lulworth Cove. Source: www.pixabay.com

When the waves hit the harder layer, they generate narrow entrances. The concavity is then formed internally, because the softer layers erode quickly.

The inlets are considered of great scenic beauty and have been of great importance for the establishment of human settlements, because they are highly protected and their waters tend to have little waves.

Archaeological remains dating back more than 7000 years have been found in Ferriter Inlet in Ireland. Similarly, many inlets off the coast of England and in the Caribbean Sea served as havens for pirates.

Among the best known inlets we have Lulworth on the Dorset coast in England. In addition, MccWay Inlet on the California coast and Sydney Creek in Australia stand out.

characteristics

Morphology

The inlets are generally oval or circular in shape. They can form on the coastline of oceans, rivers, or lakes. They are small in size, up to approximately 1000 meters wide.

They present a protected entrance, which is formed by the headlands or ledges. These headlands are made up of rocks more resistant to erosion, so the openings tend to be narrow.

Internally, the inlets present a wider inlet made up of softer rocky materials.

Wave and sediment movement

The sediments that make up the beaches are moved to and from the continent by the wind. While the waves are responsible for their longitudinal movement.

In the case of the inlets, the entrance is quite closed. Therefore, the movement of the waves can be very slow. This characteristic has the advantage that it generates a calm water area that can be used in different activities.

However, when the entrance to the inlet is extremely narrow, the waves hardly move and do not carry sediment. So these end up accumulating and affecting the quality of the water within the cove.

Factors that influence the formation of inlets

To understand the process of formation of the inlets, one must know some factors that influence the morphology of the coasts.

Among some aspects of interest we have:

-Types of rock

The type and characteristics of the rocks can define the landforms that can be formed on a given coastline. Due to its hardness we have the following:

Strong or hard rocks

Igneous rocks are considered among the most resistant to erosion. These are formed by cooling and solidification of magma. Some examples are granite and basalt.

Moderately resistant rocks

They are of the sedimentary type. They are formed by accumulation and compaction of eroded materials from the earth's surface. Among others we have sandstones, chalk and limestone.

Poor or soft rocks

They are unconsolidated materials of tertiary age. They can also be deposits of glacial rocks. Some types are clays and slates.

-Chemical composition

Some rocks such as sandstones and quartzites are made almost entirely of silica. This compound is chemically inert, so it has greater resistance to erosion.

On the other hand, iron found in some sandstones and feldspars can rust. This makes them more vulnerable to marine erosion. Likewise, in limestone rocks carbonation (chemical weathering) is accelerated by salty water.

-Types of coasts

Depending on the direction and way in which the types of rock are arranged on a coast, two types can be differentiated:

Concordant costs

They present alternating layers of hard and soft rocks. They are arranged parallel to the coast. The hard rocks act as a barrier that prevents the erosion of the softer rocks.

Discordant shores

The alternating layers of hard and soft rocks are arranged perpendicular to the coast. In this way, soft rocks are quickly subjected to the erosive action of waves.

Formation phases of a cove

Inlets form when a concordant shoreline erodes. In this case, there is a layer of hard rocks facing the sea, followed by layers of less resistant rocks. Subsequently, a layer of hard rock appears towards the continent.

The waves are eroding the weakest points of this layer. It can occur in small joints or cracks in the cliff. Due to the hardness of the material, the entrance that is formed tends to be narrow.

Formation of a cove. Source: Red

In addition to the impact of the waves, there are other elements that intervene in the rupture of the hard layer. Among these we have the chemical composition of the rocks, the impact of rain and the growth of plants. All of this can contribute to faster wear of these materials.

Subsequently, the waves impact on the softer rock layers. Erosion in this area is very fast and the concavity opens. Due to the presence of a hard rock layer towards the interior, the shape of the inlets tends to be circular.

On the Jurassic coast of Dorset (southern England) there is a system of inlets. In this area, the phases of their formation have been studied. These are:

First phase

When the inlet begins to form, the first thing that happens is the erosion of the most resistant material. This is located in front of the sea, so the waves can impact on its weak points.

On the Jurassic coast of Dorset, we have the area known as Stair Hollow, where only the erosion of the harder outer layer is seen. The site is narrow, so the less resistant inner layers have not yet eroded.

Second stage

Once the opening forms, the waves can impinge on the inner layers. As they are made up of rocks that are less resistant to erosion, the concavity begins to form.

This is the case of Lulworth Inlet, which is almost perfectly circular in shape.

Third phase

This can occur on a coastline where several continuous inlets are formed. In this case, the waves continue to erode the rock layers for a long time. The headlands that define the inlets can be worn away, causing them to merge.

It has been suggested that Worbarrow Bay may have formed in this way. Indicating that the outermost hard layer formed by Portland stone was completely removed.

Examples of inlets in the world

The inlets have had great relevance in the distribution of prehistoric human settlements. In the case of freshwater inlets, there was safe access to drinking water and for hygiene. While in those of the marine type, there was great availability of food such as fish and other animals.

In Ferriter Inlet (southwest Ireland), archaeological remains of approximately 7000 years old have been found. They apparently belonged to a fishing community that inhabited the cove during the summer.

Among some of the best known inlets in some regions, we have:

Australia

In the famous Sydney Bay (Australia) is the Sydney Creek located on its southern shore. In this place the English prison was created that gave rise to the city of Sydney.

Mediterranean

In the Mediterranean area the inlets are known as coves. Some of the highlights are Santa Galdana on the island of Menorca and Caló des Moro in Mallorca (Spain). The coves of the Blue Coast are also known as Cala de Port-Miou or Cala de Morgiou.

In the Aegades Islands (Sicily) there is Cala Rossa, which owes its name to the blood shed by the Carthaginians in the first Punic war.

Caribbean Sea

Inlets are common both on islands and on mainland. In the cove of Baracoa in the province of Guantánamo (Cuba) the first European settlement was established on the island in the year 1511.

During the seventeenth century many inlets were the ideal refuge for pirate ships that roamed in search of cargo ships. Buccaneers such as the famous Blackbeard took refuge in the inlets of the island of Grand Cayman. An example is Smith's Cove.

USA

MacWay Inlet in California is famous for its waterfalls that fall directly into the sea.

UK

One of the best known inlets is Lulworth on the UK's Jurassic coast. It is frequently used as an example of the formation of this geographical feature. It has an almost perfectly circular shape, with a narrow mouth carved in limestone.

References

1. Burton J (1937) The origin of Lulworth Covem Dorsetshire. Geological Magazine 74: 377-383.
2. Davis RA (1985) Beach and Nearshore Zone. In: Davis RA (eds) Coastal Sedimentary Environments. Springer, New York, NY pp 379-44.
3. Warn S (2001) The impact of structure and lithology on coastal landforms. Geo Factsheet 129: 1-5.
4. Yasso WE (1982) Headland bay beach. In: Beaches and Coastal Geology. Encyclopedia of Earth Science. Springer, Boston, MA.
5. Zanella A, PR Cobbold and T Boassen (2015) Natural hydraulic fractures in the Wessex Basin, SW England: widespread distribution, composition and history. Marine and Petroleum Geology 68: 438-448.