Physical: Formation Flashcards
Explain the formation of a corrie?
Snow gathers in shallow, north facing hollows, high up in the mountains, where it is sheltered from the wind and sun.
The snow does not melt in spring as it is too cold.
After many years, the snow becomes compacted and turns to ice as the air is squeezed out.
Gravity causes to ice to slide downhill out of the hollow.
The ice erodes to bottom and back of the hollow as it moves by plucking and abrasion
Plucking is when the ice freezes to rocks and tears them from the ground
Abrasion is when rocks in the ice wear away the land like sandpaper.
Freeze thaw weathering also causes rocks to break up in the corrie.
After the ice age, a much deeper bowl shaped hollow is left behind.
Sometimes the bottom of the hollow fills with rain and meltwater to form a corrie loch.
Explain the formation of an arete
An arete is a steep knife edged ridge which forms between two corries.
Describe corrie formation
The steep ridge between the two corries is the arete
It becomes rugged due to frost shattering
This is when water gets into cracks in rocks and freezes at night
The water expands and after many repetitions this process can break the rock up to make the arete look very rugged.
Explain the formation of a pyramidal peak
A pyramidal peak is a rugged hilltop where 3 or more aretes meet
arete formation
The pyramidal peak is the highest point where 3 or more aretes meet
Explain the formation of a U shaped Valley
Before the ice age, there is a small V shaped valley which has been eroded by a river
During the ice age, a huge river of ice called a glacier flows into the valley from surrounding corries.
The glacier bulldozes through the valley, eroding the sides and bottom of the valley by plucking and abrasion
Plucking is when the ice freezes to rocks and tears them from the land
Abrasion is when rocks in the ice wear away the land like sandpaper
The valley gets deepened, steepened, widened and straightened by erosion
Freeze thaw weathering also causes rocks to break up on the valley sides
After the ice age, a much bigger, wider and deeper U shaped valley is left behind.
The original river now looks too small and out of place, so is called a misfit river.
Explain the formation of a ribbon loch
formation of a U shaped valley
Sometimes a deep part of the valley gets flooded with rain and melted ice. This forms a long narrow loch/lake called a ribbon lock/ lake.
Explain the formation of a truncated spur
Formation of U-shaped valley
The sides of the valley which have been straightened and steepened by the ice are called truncated spurs.
Explain the formation of a hanging valley
A hanging valley is a smaller U shaped Valley which is formed by a tributary Glacier.
U shaped valley formation
The hanging valley joins the main U-shaped Valley high above from the side.
Sometimes a waterfall forms where the two valleys meet.
Explain the formation of bays and headlands
A coastline has bands of hard and soft rock which are at right angles to the coast.
The areas of soft rock are eroded rapidly by the sea
The sea erodes these areas by:
-Hydraulic action which is the pounding of the waves and compressed air against the rocks
-Abrasion: the sand blasting effect when sand and rocks in the sea wear away the rock as they are thrown against the coast by waves.
-Solution: When chemicals such as salt in the sea dissolve the rocks.
These areas of soft rock form bays.
The areas of hard resistant rock as left sticking out into the sea as headlands.
Often sand gets deposited by weather waves in the sheltered bay to form a beach.
Explain the formation of a wave cut platform
The waves erode the bottom of the cliff to create a Wave Cut Notch as shown. The following processes erode the base of the cliff:
Hydraulic action: which is the pounding of the waves and compressed air against the rocks
Abrasion: the sand blasting effect when sand and rocks in the sea wear away the rock as they are thrown against the coast by waves
Solution: when chemicals such as salt in the sea dissolve the rocks
Eventually the cliff above collapses, the collapses material forming a rocky beach called a wave cut platform. This process continues and erodes the cliff further and further inland.
Explain the formation of a sand spit and bar
A sandy beach is deposited by small constructive waves.
Sometimes the waves approach the beach at a sideways angle, due to the prevailing wind direction and then come back out to sea at right angles due to gravity
This pushes sand sideways along the beach.
This causes the whole beach to get pushed sideways in a process called longshore drift.
The coastline suddenly changes direction at a bay.
The waves don’t have enough energy to push the sand round the corner into the bay so the sand gets deposited in open water across the bay. This creates a spit.
If the spit grows across to the other side of the bay it forms a bar
The sea trapped behind the bar is called a lagoon
The lagoon may eventually dry up to form a salt marsh.
