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Coastal Landscapes

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Geography

The coastline of the United Kingdom is an incredible 31,368 km long (this includes all the main islands). It varies from the jagged coastal landscapes of Cornwall to the low-lying muddy estuarine coast of The Wash; from the sandy beaches found in Bamburgh, Northumberland, to the almost tropical-looking Luskentyre in the Outer Hebrides.

Coastal Landscape Bedruthan Steps StudySmarterBedruthan Steps, North Cornwall. wikipedia.org

To explain coastal landscapes fully let's break them down into the different sections of the coast.

The wider coastal landscape

The coastal landscape is changing constantly through the effects of wind, waves, currents, and tides, as you will see.

The littoral zone

The littoral zone is the area of the shoreline from the sea to the land, which is subjected to wave action. It can be divided into four subzones; backshore, foreshore, nearshore, and offshore. The littoral zone is classed as a zone rather than a line because of the effects of the waves, tides, and storms. The zone is therefore constantly changing. It is a dynamic landscape and varies because of short term (individual waves, daily tides, and seasonal storms) and long term factors (such as changes in sea levels or climate change). The subzones are:

Backshore: the area of the beach above the high tide mark. It is the area immediately adjacent to the cliff face and is only affected by wave action during major storm events.

Foreshore: the area above water level at low tide but underwater at high tide. In other words, the area within the tidal range. It is also the area commonly known as the seashore.

Nearshore: the area of shallow water beyond the low tide mark, within which friction between the seabed and the waves distort the waves sufficiently, causing them to break. Also known as the breaker zone, it extends from the foreshore to the offshore.

Offshore: the area of deeper water beyond the influence of the waves. In other words, it is the zone that extends seawards.

The diagram below illustrates the zones.

Coastal Landscapes Littoral Zone StudySmarter

Littoral zone, commons.wikimedia.org

Coastal systems

A coastal landscape is generally considered to be an open system. It has input sediment brought in through various ways, and energy from waves, wind, tides, and currents. Its output includes sediment leaving through the action of waves, deposition, and transportation. Its flows/transfers refer to erosion, weathering, transportation, and deposition. Finally, it has stores/components, which are the landforms that store sediment, such as spits.

Coasts themselves are classed as high or low-energy.

A high-energy coast receives inputs from powerful destructive waves. Consequently, it has higher rates of erosion than deposition. A low-energy coast, on the other hand, is subjected to more gentle waves known as constructive waves. As a result, it has a greater rate of deposition than erosion.

Sources of energy

The interaction between the wind and the waves helps shape the coastline. Waves provide the energy for the coastal systems, tides spread that energy over a larger area, while currents spread and redistribute the energy and sediment along the coastline.

As we have seen, there are two types of waves, constructive and destructive.

  • Constructive waves are low-energy waves. They have a strong swash, which carries sediment up the beach, and a weak backwash.
  • Destructive waves are high-energy waves. They have a high downward force and strong backwash. They are responsible for some striking coastal features.

For more information on the wider coastal landscape please refer to Wider Coastal Landscape.

Coastal classification

Coastlines can be classified according to their formation process ( primary and secondary coasts); as a result of sea-level changes (submergent and emergent coasts); and as a result of plate activity (active and passive coasts). However, it is important to remember that each classification system overlaps and complements the others.

Formation processes

  • Primary coasts are formed as a result of land-based processes such as plate tectonics and erosion sedimentation.
  • Secondary coasts have been significantly changed by marine processes after the sea level stabilised. This allowed erosion and deposition processes to dominate the landscape.

Sea level changes

Submergent coasts occur where the sea level rises relative to the land. This may be due to tectonic subsidence or when sea levels rise due to a glacier melt. The sea submerges (drowns) the existing coastline. This process creates the following coastal features:

  • Rias coast: a drowned river valley with long fringes of water stretching a long way inland.
  • Glacial coast: more commonly known as fjords: glacial valleys that have been drowned as a result of sea levels rising at the end of the last ice age.
  • Concordant coastline: This is a band of differing rock types that run parallel to the coast, and the harder rock provides a barrier for the softer rock behind.
  • Discordant coastline: differing rock types run perpendicular to the coast. The different resistance levels of the rocks allow for the formation of headlands and bays.

Plate activity

  • Active coast: a coastal landscape that is characterised by mountain-building activities, such as earthquakes, volcanic activity, and tectonic motion. Active coasts are located near a plate boundary, near the tectonic activity. An example of an active coast is the rugged Pacific Coast, which is characterised by narrow beaches, steep cliffs, headlands, and sea stacks.Passive coast: They occur at the transition between the oceanic and continental crust, a non-active plate boundary. They are usually subsiding. Passive margins are characterised by wide beaches, barrier islands, and broad coastal plains. Offshore passive margins typically have a wider and flatter continental shelf and slope. Examples of passive coasts are the Atlantic and Gulf Coasts.

For more information on coastal classification, refer to Coastal Classification.

Formation of coasts

There are two main types of coasts.

Rocky / cliffed coastlines: these have cliffs varying in height from a few feet to hundreds of meters. The cliffs are made of rock. However, the hardness of the rock varies.

Coastal plains: the land gradually slopes towards the sea across an area of deposited sediment. Sand dunes and mudflats are the most common examples. If the coastline is a sandy coast it will be composed of sands, shingles, and cobbles. If it is estuarine (alluvial) it will be composed of mud (clays and silts).

Rocky coasts

Coasts with a steep cliff face can be found in high-energy environments where the waves pound the face of the cliff throughout the year. A gentler cliff profile tends to indicate a low-energy environment. There are two main cliff types.

Marine erosion dominated: these cliffs tend to be steep and unvegetated, with little rock debris at the base, because any debris is quickly broken up by the waves and carried away. Cliffs that are not actively eroded away at their base by waves will have shallower, curved profiles and low relief.

Sub-aerial processes dominated: as we see in Coastal Formations, the sub-aerial processes of surface runoff, erosion and mass movement (landslides), slowly move rock and sediment downslope. Limited marine erosion means that it will not be removed.

Features found on a rocky coast:

  • Headlands.
  • Cliffs.
  • Wave-cut platform (shoreline platform).

Coastal plains

Sandy coastlines are generally found in low-energy environments. These coasts are relatively flat, low-relief areas adjacent to the sea. These coasts are where the rate of deposition exceeds that of erosion. Dune vegetation plays a critical role in stabilising the coast and preventing erosion. Beaches are made of a gradual build-up in and across bays of either sand or shingle, or a mixture of both.

There are two types of beach:

  • Swash-aligned waves break in line (parallel) with the coast. The swash and backwash move material up and down the beach.
  • Drift-aligned waves break at an angle to the coast. Material is transported by longshore drift.

Features associated with a sandy coastline:

  • Ripples.
  • Spits and tombolos.
  • Bars and barrier beaches.
  • Offshore bars.
  • Sand dunes.

Estuarine coastlines are found at the mouths of rivers. The flow of water from the river meets with the incoming tides and waves from the sea. This causes the water flow to virtually cease and causes the water can no longer carry its sediment in suspension.

For more information on this topic please refer to Formation of Coasts.

Geological structure

The geological structure has an important influence on the morphology and erosion rates in a coastal landscape. There are three key elements to geological structure.

  • Strata: the different layers of rocks within an area, and their relation to each other.
  • Deformation: the degree to which rock units have been deformed, either by tilting or folding or by tectonic activity.
  • Faulting: the presence of major fractures that have moved rocks from their original position.

Strata

The strata influence geological structure by producing two dominant types of coasts.

  • Concordant - Here beds, or layers, of differing rock types are folded into ridges that run parallel to the coast. The outer hard rock (ie granite) provides a protective barrier to erosion of the softer rocks (ie clays) further inland. Concordant coasts are also known as Dalmatian coasts, after the Dalmatian region of Croatia, or Pacific coasts, after the coastline of Chile in South America.
  • Discordant - These occur when bands of different rock run perpendicular to the coast. The differing resistance to erosion of the rocks leads to coastlines dominated by headlands and bays. Part of the Dorset coastline, north of Durlston Head, is a clear example of a discordant coastline. Discordant coasts are also known as Atlantic coasts, after the Cork coastline in the Republic of Ireland.

Deformation and faulting

Cliff profiles are influenced by different aspects of geological structure but certain characteristics are dominant.

  • Where the rock is resistant to erosion.
  • The dip of the strata in relation to the coastline. This means the angle of the rock strata in relation to the horizontal. Sedimentary rocks are formed in horizontal layers but can be tilted by tectonic forces. When this is exposed on a cliff coastline it has a dramatic effect on the profile of the cliff.
  • Joints are fractures in rocks created without displacement. They occur in most rocks, often in regular patterns, dividing rock strata up into blocks with a regular shape.
  • Faults are major fractures in the rock created by tectonic forces, with the displacement of rocks on either side of the fault line. They represent a major weakness within the rock layer.

Fissures are much smaller cracks in the rocks, often only a few centimetres long. However, they still represent a weakness that erosion can exploit.

For more information, please refer to Geological Structure.

Lithology

Lithology refers to the physical properties of a rock. The lithology at the coast affects the speed at which it erodes or recedes.

Most cliffed coasts are not made from only one rock type. They are composite cliffs with different rock layers, sometimes from different geological periods. As a result, a complex cliff profile is produced. The resistance of the cliff to erosion will be influenced by its weakest rock type, and also its permeability.

There are three major rock types; igneous, sedimentary, and metamorphic.

  • Igneous rocks like granite, basalt, and dolerite erode very slowly, at a rate of less than 1mm per year. They have few joints, and have few weaknesses, and are crystalline.
  • Metamorphic rocks like slate, schist, and marble are also crystalline and resistant to erosion. They erode faster than igneous rocks, though; at the rate between 1mm-10cm per year.
  • Sedimentary rocks like sandstone, limestone, and shale are clastic. As with shale, they have many bedding places and fractures and are vulnerable to erosion, from 10cm-several metres per year.

For more information, refer to Lithology and Vegetation.

Coastal Landscapes - Key takeaways

  • The coastal landscape is constantly changing through the effects of wind, waves, currents, and tides.

  • The littoral zone is the area of shoreline from the sea to the land. It is constantly subjected to the actions of waves. This zone is divided into four zones, the backshore, foreshore, nearshore, and offshore.

  • A coastal landscape is generally considered to be an open system. This is because it has input, outputs, flows/transfers, and store/components.
  • Coasts themselves are classed as high or low-energy.
  • There are two types of waves: constructive and destructive.
  • Coastlines can be classified according to their formation process, as a result of sea-level changes and through plate activity. Each of these processes overlaps and complements each other.
  • Submergent coasts occur where the sea level rises relative to the land.
  • Active coasts are those that are located near a plate boundary, near the tectonic activity.
  • Passive coasts occur at the transition between the oceanic and continental crust.
  • There are two main types of coasts: rocky/cliffed and coastal plains.
  • There are three key elements to geological structure: strata, deformation, and faulting.
  • Lithology refers to the physical properties of a rock. The lithology at the coast affects the speed at which it erodes or recedes.

Coastal Landscapes

A coast is an attractive place for humans to live, visit (for tourism), and work (in fishing, for example). But this has a lot of detrimental effects on the natural ecosystems of the coast. Among other things, humans on the beach cause issues by leaving their rubbish behind them, walking over natural vegetation, and disturbing breeding birds.

A coastal landscape is formed by waves via a combination of the following processes: erosion, deposition, and transportation. The force of the waves depends on which of these processes is dominant.

A section of coastline that has a variety of coastal features created either through erosion or deposition. It can be distinguished from other coastlines by which process is dominant.

It is important because it helps us understand natural events and sea-level changes. For example, sand dunes are important for monitoring the impact of changes in sea level, because they erode quickly when the sea is rising.

It depends upon whether erosion or deposition is the dominant process, the lithology of the rocks present, and which sub-aerial processes are operating on the rocks.

Final Coastal Landscapes Quiz

Question

What features can be found at an Emergent Coast?

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Answer

Raised Beaches, Wave cut platforms., Relic cliffs, Sea cliffs, Stacks, Tombolo and 

caves

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Question

What features can be found at a Submergent Coast?

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Answer

Rias Coast, Glacial Coasts- Fjords, Concordant coastline, and Discordant coastline

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Question

Describe where you would find an Active Coast?


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Answer

In a coastal region characterised by mountain-building activity, including earthquakes, volcanic activity, and tectonic motion resulting from the movement of tectonic plates. Active coasts are those located near a plate boundary and thus near tectonic activity.

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Question

Describe where you would find a Passive coast?


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Answer

 In areas where the transition between oceanic and continental crust which is not an active plate boundary. Passive margins are characterised by wide beaches, barrier islands, broad coastal plains.

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Question

Coastlines can be classified by what?


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According to their formation processes, Primary and Secondary Coasts. Sea-level changes, waves, and plate activity.

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Primary coasts are formed by what processes?


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 They are formed by land-driven processes like plate tectonics, land erosion, and sedimentation rather than ocean processes.

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 Secondary coats have been significantly changed by what processes?


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Answer

These are coasts that marine processes have significantly changed after the sea level has stabilised.


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As a result of marine processes, what has been allowed to occur on secondary coasts to shape them?


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Answer

Erosional and depositional processes dominate the shaping of the landscape.

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Question

 How is a raised beach formed?


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Answer

Raised beaches are formed when the fall in the sea level leaves beaches above the high tide mark. Over time, beach sediment becomes vegetated and develops into the soil. 


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What feature is formed when sea arches collapse?


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Stacks.

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Question

 What is a rias coast?


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They are drowned river valleys with long fringes of water stretching a long way inland, including their tributary valleys. They are at their widest and deepest nearest to the sea and get progressively narrower and shallower inland. Tidal changes will often reveal extensive areas of mudflats.

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 What is a glacial coast, fjords, and how is it formed?


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These are like Rias, but they are glaciated valleys that rising sea levels have drowned at the end of the ice age. They are relatively straight and narrow, with very steep sides. They have a shallower mouth caused by a raised bit of ground, called a threshold, formed by the deposition of material by the glacier. They have the typical steep-sided and deep cross profile.


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Question

 Describe a low energy coast?


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These coasts are those that are sheltered from storms and swells by adjacent topographical features (barrier island, reef, embayment, shoal, headland), also by their position concerning prevailing wind direction, their place in a climatic belt, by gentle offshore topography, or by a combination of all these factors.

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Describe a high energy coast?


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High energy coasts are usually characterised by strong wave action, especially during the winter months, and where the rate of erosion exceeds the amount of material deposited. The main features are big cliffs and.

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Question

What are Active coast characterized by?


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Answer

It is characterised by mountain-building activity, including earthquakes, volcanic activity, and tectonic motion resulting from the movement of tectonic plates

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 Steep cliffs are generally found in what type of environment?

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Steep cliffs are generally found in high energy environments.

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Gently, cliffs are generally found in what type of environment?

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They are generally found in a low-energy environment.

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There are two main types of cliffs: what are they?


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They are marine erosion and sub-aerial processes dominated.

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Explain what a Marine erosion-dominated cliff is.


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These cliffs tend to be steep, unvegetated and there is little in the way or rock debris at the base of the cliff; this is because it is quickly broken up by the waves and carried away. Cliffs that are not actively eroded at their bottom by waves will have shallower, curved profiles and low relief.

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Question

Explain what a sub-aerial dominated cliff is.


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Answer

On these cliffs, the sub-aerial processes of surface runoff erosion and mass movement (landslides) slowly move rock and sediment downslope; the limited amount of marine erosion means that it will not be removed.

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Question

What features can be found on a rocky coastline?


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Headlands, Cliffs, Wave cut platform (Shoreline platform).

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There are two types of beaches. What are they?


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Swash Aligned Coasts and Drift aligned coasts.

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Names some of the features associated with a sandy coastline.


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Spits and tombolos, Bars and barrier beaches, Offshore bars, and Sand dunes.

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Complete the following sentence. Offshore bars are where deposits of sand and shingle have situated some distance from a coastline; these usually lie ……… sea level, becoming visible only at …...... tide.


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Offshore bars are where deposits of sand and shingle have situated some distance from a coastline; these usually lie below sea level, becoming visible only at low tide.

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Describe what a spit and tombolos are.


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 Spits and tombolos are long, narrow stretches of sand or shingle that protrude into the sea or across an estuary.

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Name three critical elements of geological structure.

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Strata, deformation, and faulting.

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Strata refer to what?

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Answer

The different layers of rocks within an area and how they relate to each other.


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Add the missing words. Deformation is the degree to which rock units have been deformed, either by _____ or folding, by _____ activity.


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Answer

Deformation is the degree to which rock units have been deformed, either by tilting or folding, by tectonic activity.

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Geological structure types produce two dominant types of coasts. What are they?


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Answer

Concordant and discordant coasts.

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Complete the sentence. Concordant coasts form if the rock layers are running _____ to the coast.


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Answer

Concordant coasts form if the rock layers are running parallel to the coast.

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A concordant coast is also known as what?


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Pacific coast.

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What is a haff coast?

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Haff coasts are another type of concordant coast, e.g., the southern fringes of the Baltic Sea. Long sediment ridges topped by sand dunes run parallel to the coast just offshore, creating lagoons (haff) between the ridge and the shore.

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Question

Complete the sentence. Where bands of different rock types run _____, you will see a discordant coastline.


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Answer

Where bands of different rock types run perpendicular to the coast, you will see a discordant coastline.

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What is another name for a discordant coast?


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Atlantic coast.

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Question

What is a prominent feature of a discordant coastline, and why?


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Headlands and bays. This is due to the rocks’ differing resistance to erosion. A hard rock type, which is resistant to erosion, will create a point of land that extends out into the sea, a promontory. A softer rock type is easily eroded, creating a bay.

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Question

What does dip mean when referring to a cliff profile?

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Answer

When referring to a cliff profile, dip means the angle of the rock strata in relation to the horizontal. For example, sedimentary rocks are formed in horizontal layers but can be tilted by tectonic forces.

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What are joints? 


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Fractures in rocks created without displacement. They occur in most rocks, often in regular patterns, dividing rock strata into blocks with a normal shape.

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Explain what faults are.

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Major fractures in the rock caused by tectonic forces; the rocks on both sides of the fault line will be shifted due to tectonic forces. They represent a significant weakness within the rock layer. 

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Question

What does lithology refer to?

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Lithology refers to the physical properties of a rock

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How many different rock types are there?

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There are three main rock types.

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Name the three main rock types?


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Igneous, sedimentary, and metamorphic.

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What rocks fall within the sedimentary category?

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Limestone, sandstone, chalk, and shale are sedimentary.

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Why is chalk porous?


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It has air spaces between the particles, which make it porous.

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What are the characteristics of sedimentary rocks?


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They have been compacted and hardened over time by lithification, are more susceptible to erosion and weathering, cover 75% of the earth's surface, and are generally not crystalline. They also have a fast erosion rate of about 2-6 cm per year. 

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Which rocks are igneous?


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Basalt, granite, and dolerite are igneous rocks.

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What are the characteristics of igneous rocks?


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They are crystalline; they have interlocking crystals that make them very strong. They are resistant to erosion and weathering and are impermeable. The crystals in the rock increase its strength – reducing the lines of weakness which can be exploited.

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Which rocks are metamorphic?

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Slate, marble, and schist are all metamorphic rocks.

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What is foliation?

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This is where all the crystals originate in one direction – this produces weaknesses.



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Which of the three main rock types erode the quickest?


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Sedimentary rocks erode very quickly – about 2-6 cm per year.

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Question

What is unconsolidated sediment?


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Answer

This is material such as sand, gravel, clay, and silt, which has become compacted and cemented to become sedimentary rock. It has not undergone the process of lithification (compacted and hardened). It is loose and easily eroded.

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