Glaciers (Lake District) Flashcards
What is freeze thaw weathering?
When water seeps into the cracks of the rocks and freezes over night, expands, and breaks pieces of load off of the mountain/ glacier.
What is plucking?
When meltwater surrounds a piece of load and freezes around it, as the glacier moves forward, the load gets plucked off of the glacier floor into the glacier.
What is abrasion?
When the force of the ice and it’s sediments beneath it start to grind along the glacier,, wearing it down.
Name types of erosion that occur in a glacier?
- abrasion
- plucking
- freeze thaw weathering
Name the two type of glacial movement:
- rotational slip
- basal sliding
What is rotational slip?
when a glacier moves in a circular motion that may erode hollows in the landscape forming corries
What is bulldozing?
when the glacier’s snout gathers ground till as it advances down the glacier, eventually when it reaches the bottom of the glacier it leaves ridges of till at the bottom as the glacier retreats again.
How is a corrie formed?
snow gathers in depression on a mountain side, more often on the north facing side due to the lack of sunlight hitting it. Over time, the snow compresses itself to form ice crystals under its own weight, and eventually turns into ice. As the glacier becomes more denser it becomes heavier, and the bottom of the glacier starts to slightly melt into meltwater, and because of gravity, helps the glacier to move by rotational slip. Plucking can occur at the bottom of the corrie, where parts of the glacier floor get surrounded by this meltwater, freezes and gets pulled away from the rock into the glacier. Freeze thaw weathering also occur on the steep back wall where water expands into cracks of the wall breaking pieces off. The broken off sediment turns into erosional tools for the glacier to abrade deeper into the corrie. As the glacier moves in the corrie, it starts to leave it, and as it passes over the corrie lip its energy decreases and lots of sediment get deposited there. Over time the glacier will melt in the corrie forming a tarn.
What is till?
Unsorted sediment with a range of sizes and shapes.
What percentage of ice covered the earth in the last ice age?
32% covering the earths land and 30% covering the seas.
What is basal sliding?
When a glacier forms meltwater beneath itself due to its weight, this lubricates the bottom of the glacier allowing the glacier to move and slide.
What is an arête and how is it formed?
An arête is a ridge of land between two glacier valleys or at the back of a corrie.
It forms due to the erosional processes (abrasion and freeze thaw weathering) occur on two adjacent corries/ glacier valleys. Basal sliding occurs on both corries, meaning that abrasion occurs on the steep back wall, making them more vertical and the corries deeper, which forms the thing ridge.
What is a pyramidal peak?
When three corries or glacier valley’s meet at one point and their arêtes all join up in a single mountain peak. Due to the basal sliding and rotational slip, plucking and abrasion occur making the glaciers deeper and freeze thaw weathering occurs no the back walls making them more vertical and the pyramidal peek pointed and distinguished.
How is a glacial trough formed?
-As a glacier progresses down a V-shaped valley due to gravity, the processes that occur can shape the landscape differently.
-As a glacier collects more snow, it compresses and becomes denser, this increases its erosional power to abrade and pluck away at the valley grinding the floor, making it deeper.
-Over time the glacier will abrade and pluck at the sides of the V-shaped valley, making the walls more vertical and rocky.
-The valley floor also gets abrades downwards by the sediment at the bottom of the glacier making the floor wider and flatter.
-Plucking occurs, breaking pieces of the valley off from the sides and bottom by the meltwater freezing around rocks, which gives the glacier more erosional tools as it gets transported down the glacier.
-When the glacier retreats and melts away it reveals a U-shaped valley, a glacial trough, characterised by its deep vertical sides and its flat valley floor. In the middle is a misfit river, which no longer fits in with the huge disproportionate valley. Above, glacial tributaries have also melted away, leaving hanging valleys which waterfalls fall from into the misfit river below.
-The moraine that the glacier has deposited is fertile, which vegetation can grow from.
What are drumlins and how are they formed?
A drumlin is an egg-shaped mound of glacial till that has collected in groups forming a hill like shape on the glacier floor. They are characterised with a toss end (a steep end) and a tapered end, this is caused when the glacier snout approaches a stickier, well saturated part of the ground, making the till more mouldable. It bulldozes this sediment collecting it in a mound until the glacier starts to progress and climb over the mound, due to the glacier’s weight the mound gets flattened on one side creating the tapered side of the drumlin which is revealed once the glacier melts away.
