physical landscapes - glacial landscapes in the UK Flashcards
what is weathering
the breakdown of material where it stands
e.g.freeze-thaw weathering
describe the process of freeze-thaw weathering
•water seeps into cracks in a rock face (may be water from summer rainfall or snow melt)
•water expands by 10% when it turns to ice, this expansion puts pressure on the rock either side of the crack, prising it apart and causing the crack to tear open
•process repeats and over time, large blocks of rock can be shattered apart by repeated cycles of this weathering process
what is the name for the fragments of rock broken away from the mountainside via freeze-thaw weathering
scree
where are glaciers formed
They are formed in areas of high snowfall in winter and cool temperatures in summer. This means that the snow that accumulates in the winter isn’t lost by melting or evaporation during the summer. These conditions occur in polar and high alpine regions. Usually on north facing mountains.
describe plucking
when meltwater beneath a glacier freezes and bonds to the base of the glacier to the rocks below as the glacier moves it plucks these rocks leaving behind a jagged landscape
describe abrasion in glacial erosion
•sandpaper effect caused by the weight of the ice scouring the valley floor
•it leaves a smooth polished surface
•striations (sharp grooves) caused by large rocks beneath the ice can often be seen
what is bulldozing
when a glacier moves forward it can act like a giant earthmover, bulldozing piles of rock debris in front of it to create a high ridge called a moraine, the furthest advance of a glacier is marked by a terminal moraine, this is because the glacier has a huge mass
what’s an arête
an arête is a narrow ridge formed when two corries have eroded back to back making the land between them thinner and thinner
how is a pyramidal peak formed
a pyramidal peak is formed when three or more corries erode back to back to form a single peak where the arêtes meet
describe the contour lines around a corrie
corries have tightly packed contours in the U-shape around then
what are glacial troughs
glacial troughs are flat valleys with very steep sides, there are no contour lines on the bottom of the valley but they’re tightly packed on the sides
what are drumlins
they are egg shaped hills, composed of mounds of till, caused by glacial deposition (ice bulldozed down the valley) and can show the direction the ice was travelling in
what type of lake could you find in a U-shaped valley
a ribbon lake
define lateral moraine
material comes from freeze-thaw weathering of the high valley sides, which is deposited along both sides of the glacier/that runs along edges of a glacial trough
define medial moraine
•these are the ridge of rocks running down the middle of the valley formed by two lateral moraines from two glaciers coming together
define terminal moraine
rocks deposited in a ridge at the maximum advance of the glacier (material builds up if the glacier stays in the same place for a long period of time)
describe how the blunt and tapered end of a drumlin is made
blunt end - glacier meets a bump in land or a big boulder so accumulates and then goes around it
tapered end - some material gets dragged and deposited
what have developed on valley floors - give an example
settlements have developed on dry, flat sections of the area’s wide, U-shaped valley bottoms, an example is Kewick, which the River Derwent now flows into
draw the steps of how a corrie is made
draw three images:
first image - a high mountain peak with a small dip near the top and show a small glacier forming and some snow
second image - zoom into the small glacier from first image and show cracks forming at the back of the glacier and label it with freeze-thaw weathering, show scree falling from the cracks and into the glacier and at the bottom of it, label the glacier with glacier and then label the backwall and plucking next to the backwall label and abrasion at the bottom of the glacier, label the land at the end of it with reduced erosion as the ice is thinner
third image - label a very steep backwall and draw it, label a pile of scree/scree slope at the bottom of the wall and at the start of the curve, then label much deeper rock basin at the bottom of the corrie and finally label the rock lip
describe how corrie is made
can use images
•snow accumulates high up in a hollow and is compressed into ice
•over time the snow becomes glacial ice and there is more ice than the depression can hold and some of it starts to flow to lower levels
•ice becomes frozen to the back of the hollow and plucking occurs as blocks of rock are pulled away as the ice moves downhill. This makes the back wall steeper and these rock fragments become incorporated into the glacier.
• freeze-thaw weathering occurs at the top of the slope producing scree which becomes incorporated into the glacier
• the hollow deepens where the ice is thickest due to abrasion. Rock debris acts as tools to wear away the bottom of the hollow.
• there is less erosion at the front where the glacier leaves the corrie hollow to flow down the valley; a rock lip forms here as a result of less powerful erosion
• When all the ice has melted a tarn (lake) forms
what is a landform
a natural and distinctive feature on earth’s surface caused by geographical processes e.g. erosion or deposition
what are characteristics and formation of landforms resulting from erosion during the glacial period
corries, arêtes, pyramidal peaks, truncated spurs, glacial troughs, ribbon lakes and hanging valleys
how do glaciers move in the summer
meltwater lubricates allowing the glacier to slide downhill, this type of movement can be very sudden and is called basal slip, in hollows high up on the valley sides, this movement is more curved and is called rotational slip
how do glaciers move in the winter
the glacier becomes frozen to the rocky surface, the weight of the ice (glacier) and the influence of gravity causes individual ice crystals to change shape in a plastic way, this is called internal deformation and causes the glacier to move slowly downhill
what is the opposite of glacial periods
interglacial periods