Lithosphere Flashcards
Explain the conditions and processes which encourage the formation of landslides (6)
- These occur on slopes that of 15 degrees or more
- These occur where there is no vegetation binding rocks together
- These occur where the bedding planes run parallel to the angle of the slope
- They are caused by wave action undercutting a cliff
- They are further caused by heavy rain entering cracks and lubricating the rock
- The slabs of rock then slide over one another
Explain the conditions and processes which encourage the formation of scree slopes (rockfalls) (6)
- It occurs on slopes greater than 40 degrees
- It occurs where there is little or no vegetation
- The rocks must first be loosened by freeze thaw weathering, so well jointed rocks suffer most
- These then fall under gravity and accumulate at the foot of slopes as scree slopes
- They come to rest at angles between 25 to 30 degrees
- The larger particles however travel further, so the scree slope is graded
Explain the conditions and processes which encourage the formation of landslumps/landslips (6)
- These occur on slopes of 15 degrees or greater
- These occur where there is no vegetation binding the rocks togethher
- These occur where the bedding planes run horizontally
- These occur where hard rock overlies soft rock
- They are caused by wave action undercutting the soft rock at the base of the cliff
- They are further caused by heavy rain entering cracks and lubricating the rock
- They are further caused by soft rock collapsing under the weight of the hard rock, causing rocks to suddenly slump downwards along a curved sheer plane
Explain how a corrie is formed (6)
- A corrie usually begins as a small hollow on the coldest part of the mountain high up and facing North
- During the Ice Age snow collected in the hollow, turned into ice, filled up the hollow and moved down-valley as a glacier
- The back of the hollow was worn back by freeze-thaw weathering, where meltwater enters the crack, freezes, expands by 9% and forces the crack wider until rock breaks off
- The back of the hollow is also eroded by plucking, where the glacier freezes onto the rock and then plucks away loose rock as it moves downwards
- The base of the hollow is eroded by abrasion, where the pieces of rock eroded from the back of the hollow are embedded in the bottom of the ice and the glacier scrapes and wears down the rock underneath
- The hollow becomes deeper and steeper and forms a corrie
Explain how an arête is formed
EXPLAIN HOW A CORRIE IS FORMED
• If there are multiple corries being worn back and steepened next to each other, a steep knife-edge ridge is formed separating the two corries
Explain how a pyramidal peak is formed
EXPLAIN HOW A CORRIE IS FORMED
- When several corries on the same mountain are worn back and steepened and form aretes separating them, a peak is formed at the top
- This peak is then sharpened by frost action
Explain how a U-Shaped valley is formed (6)
- These are formed when a glacier moves down a regular V-Shaped valley
- The glacier plucks and abrades the base and sides of the valley, changing it to a U shape
- The greater erosive power of a glacier also over-deepens the valley
- The slopes above the glacier are not steepened and are called benches
- After glaciation, weathering causes scree to collect at the base of the valley sides
- Rivers then take over, meandering across a valley far too big for them to have eroded called misfit streams
Explain how a limestone pavement is formed (8)
- Limestone pavement is a bare limestone surface, made up of clints separated by grykes
- Clints are separate blocks of limestone, and the grykes are the deep fissures in between
- The surface is bare because glaciers have scraped the surface clean of soil
- It is also bare becaue the soil has only formed very slowly since the ice age
- The grykes have formed by chemical weathering, where rain picks up carbon dioixide as it fall from the atmosphere
- The rain becomes a weak carbonic acid and dissolved the calcium in the limestone
- As the rain runs down the cracks in limestone it dissolves the sidesm widening the cracks to make them fissures called grykes
- The grykes also form by freeze-thaw weathering, where the frozen water in the fissure expands and widens crack
Explain how stalagmites and stalactites are formed (6)
- They are columns of calcium in a limestone cave
- Rainwater passes though limestone and dissolves much calcium carbonate
- Water drips from cave ceiling, some drops and despots on floor or stays on celing and despits there
- Grow upwards or dowwards slowly
- Forms stalactites from ceilings, and stalagmites from floor
- if they grow more, they meet in middle and form a column
Explain how a headland is formed (6)
- When alternating bands of hard and soft rock
- Less resistant rock eroded more quickly
- More resitant rock sticks out
- Once formed, resistant takes most of wave energy, whereas bay is sheltered
- The resistant rock is eroded by the waves
- Eventually the hard rock recedes to the bay level and process is repeated
How are sandspits formed? (8)
- It’s an extension of the beach into open water
- occurs along beach coastlines which have long shoredrift from one main direction
- it also occurs where coastline abruptly changes direction
- it eventually builds up above sea-level to form an extension to the the beach
- once formed, lsd continues to move material along it, and so sandspit extends into open water
- water gets deeper, so sandpit extended less
- the wind from another direction is strong enough to hook sandspit round