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Today, weβre exploring high rocky coasts. Can anyone describe how these coasts look?
They have steep cliffs that drop straight into the water!
Exactly! The hillsides drop sharply, creating a dramatic landscape. Why do we think these coasts are so indented?
Is it because of erosion from waves?
Thatβs correct, Student_2! The waves erode the cliffs, causing them to retreat and shape the coastline. Remember, we often describe these features as having fjords.
What happens to all the materials that are eroded?
Good question! The materials break down into smaller fragments, which can eventually end up offshore. This process is essential for forming underwater features.
So, the coast changes over time, right?
Yes, precisely! Over time, erosion changes the coast, creating features like wave-cut platforms. Let's summarize: High rocky coasts have steep cliffs, are highly indented, and primarily experience erosional processes.
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Now, letβs dive deeper into what happens when waves hit these cliffs. What forces do you think are at work?
Waves hit really hard against the rocks, which must cause a lot of wear and tear!
Exactly! The immense force of the waves leads to significant erosion. This makes cliffs recede and creates features like wave-cut platforms at their bases. Can anybody explain what happens to materials as they get eroded?
They get broken down into smaller pieces and get smoother over time, right?
Correct! These smaller fragments may move offshore due to longshore currents. What role do those currents play in shaping coastal landscapes, do you think?
They must help deposit those materials somewhere along the coast!
That's right! In summary, waves cause strong erosion on high rocky coasts, leading to cliff retreat and the formation of platforms, with materials transported and deposited by underwater currents.
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Letβs talk about wave-cut platforms. Who can define what that is?
I think itβs a flat area at the base of a cliff, created from the waves hitting the rock?
Spot on! Wave-cut platforms form when waves erode the base of cliffs. Why do you think this is an important feature in coastal geography?
Maybe because they show how much the coastline has changed over time?
Exactly! They are indicators of erosion history. If we look closely, we can see the gradual retreat of the cliffs. Can anyone summarize how these features impact the overall coast?
They help transform harsh coastlines into smoother ones over time.
Well said! Wave-cut platforms are essential as they illustrate the erosion process and its effect on the coast.
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Finally, let's discuss what happens after erosion. What types of sedimentary features can form?
Could it be beaches or barriers?
Yes! As the coastline becomes smoother, materials deposit as beaches, barrier bars, and spits. What leads to the formation of these features?
I guess itβs the sediment carried by longshore currents?
Correct! The balance of erosion and deposition results in diverse coastal landscapes. Can anyone reiterate the importance of understanding these coastal processes?
It helps us see how coastlines evolve and adapt to changing environments.
Exactly! To summarize, while high rocky coasts start with strong erosion, they eventually contribute to forming various depositional features, enhancing the coastline's resilience.
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Along high rocky coasts, intense wave action results in steep cliffs, wave-cut platforms, and minimal deposition. The coastline features deep fjords, and as erosion progresses, materials from cliffs erode and contribute to offshore deposits, gradually shaping the landscape.
High rocky coasts are defined by their sharply indented shorelines where rivers appear to be inundated. The hillsides face steep drops into the water, leading to the formation of glacial valleys known as fjords. Erosion dominates this landscape, resulting in minimal deposition initially. As waves aggressively strike the rock faces, they sculpt the cliffs, causing them to retreat over time, leading to the formation of wave-cut platforms at their bases.
Materials eroded from these cliffs are gradually broken down into smaller fragments and may become rounded pieces found offshore. With the progression of erosion, as the coastline smooths out, the material contributes to the creation of wave-built terraces in front of these cliffs. Eventually, this erosion generates a significant quantity of sediment that can be deposited as longshore currents transport it along the coast, forming beaches and bars. Thus, while the high rocky coasts are primarily erosional due to their geographic features, they can also lead to unique depositional phenomena such as barrier bars and spits, following the reduction of cliff irregularities.
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Along the high rocky coasts, the rivers appear to have been drowned with highly irregular coastline. The coastline appears highly indented with extension of water into the land where glacial valleys (fjords) are present. The hill sides drop off sharply into the water. Shores do not show any depositional landforms initially. Erosion features dominate.
High rocky coasts are defined by their steep and irregular contours. The rivers found in these areas seem submerged, creating a rugged appearance known as an indented coastline. This occurs because, in the past, glaciers have carved out deep valleys (fjords) that extend inland, leading to sharp drops where land meets the sea. At these coasts, you wonβt see many areas where sediments are built up to form new land (depositional landforms) due to the overwhelming force of erosion.
Think of a giant sandwich where each layer is distinct and layered at an angle. Now imagine the top of the sandwich is missing, exposing the fillings underneath. This is similar to how high rocky coasts look; steep cliffs drop into the water below, resembling the sharp drop of an exposed sandwich filling.
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Along high rocky coasts, waves break with great force against the land shaping the hill sides into cliffs. With constant pounding by waves, the cliffs recede leaving a wave-cut platform in front of the sea cliff. Waves gradually minimize the irregularities along the shore.
The power of waves crashing against cliffs shapes high rocky coasts significantly. Over time, as waves continuously hit the steep cliffs, they erode the base of the cliffs, causing them to retreat. This process creates a flat area at the water's edge called a wave-cut platform. As the waves continue to wash against the land, they smooth out the edges, making them less jagged.
Imagine repeatedly pushing a rock with a basketball. Each push wears down the bottom of the rock, making it flatter until it resembles a table surface. This is like how waves constantly attack cliffs, smoothing them out over time until they form a flat area in front.
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The materials which fall off, and removed from the sea cliffs, gradually break into smaller fragments and roll to roundness, will get deposited in the offshore. After a considerable period of cliff development and retreat when coastline turns somewhat smooth, with the addition of some more material to this deposit in the offshore, a wave-built terrace would develop in front of wave-cut terrace.
As cliff erosion continues, bits of rock and sediment break away from the cliffs. These fragments are worn down by waves and currents and eventually settle in deeper water offshore, creating new landforms. Over time, as the cliffs continue to erode and the offshore areas build up with sediment, they can form a wave-built terrace, which is like a sloped shelf extending into the sea.
Think of how a sculptor carves a statue from a large stone block. As the sculptor works and chips away at the stone, small pieces fall away. Eventually, those small pieces might pile up at the base, creating a platform that builds up over time. Similarly, the erosion of cliffs allows materials to accumulate offshore, forming terraces.
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As the erosion along the coast takes place, a good supply material becomes available to longshore currents and waves to deposit them as beaches along the shore and as bars (long ridges of sand and/or shingle parallel to the coast) in the nearshore zone. Bars are submerged features and when bars show up above water, they are called barrier bars. Barrier bar which get keyed up to the headland of a bay is called a spit. When barrier bars and spits form at the mouth of a bay and block it, a lagoon forms. The lagoons would gradually get filled up by sediments from the land giving rise to a coastal plain.
Erosion not only shapes the cliffs but also produces large amounts of sand and gravel. These materials are moved by ocean currents and waves to form beaches and submerged ridges known as bars along the coastline. When these bars extend above the water, they become barrier bars. If they connect to the land, particularly to a headland, they form spits. Over time, if these spits block water bodies like bays, lagoons form. Eventually, these lagoons can fill in with sediment, altering the landscape into flat coastal plains.
Consider a riverbank where sand and pebbles are pushed to one side by flowing water. After a while, this buildup creates a small island or sandbar. Similarly, on high rocky coasts, as waves move materials from the cliffs, they create beaches and other features along the shoreline.
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Key Concepts
Erosion: The process by which rocks and sediments are worn down and removed from a surface.
Coastal Features: Includes cliffs, platforms, beaches, and bars formed through the interactions of waves and sediment.
Transport of Sediment: Longshore currents play a crucial role in moving sediment which can lead to depositional features.
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The coastline of Norway features many fjords, characterized by steep cliffs and deep waters.
California's Big Sur showcases wave-cut platforms and cliffs resulting from the relentless wave action.
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Cliffs so steep, where waters leap, erosionβs song, they sing along.
Imagine a mountain standing proud, waves crash, and slowly it bows, revealing secrets in each erode, a fjordβs beauty starts to unfold.
C.R.E.E.P. - Cliffs Retire, Erosion Expands, Platforms emerge!
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Review the Definitions for terms.
Term: Fjord
Definition:
A steep, narrow inlet of the sea between cliffs, often formed by glacial erosion.
Term: WaveCut Platform
Definition:
A flat area at the base of a cliff that has been eroded by wave action.
Term: Cliff Retreat
Definition:
The gradual recession of the cliff face due to the erosive action of waves.
Term: Longshore Currents
Definition:
Currents that move parallel to the shoreline, responsible for transporting sediment along the coast.
Term: Barrier Bar
Definition:
A long ridge of sand or shingle lying parallel to the coast that can develop from deposition.