Glacial Landforms Flashcards
All 17 cards in this deck
What are the steps in the formation of a corrie?
e.g. Cwm Idwal, Snowdonia- Snow collects in a hollow on a mountainside and compacts into ice.
- Rotational slip and abrasion deepen the hollow; plucking and freeze-thaw steepen the back wall.
- Thinner ice at the front leaves a rock lip, so a tarn fills the hollow after melting — e.g. Llyn Idwal.
True or false? In the UK, corries are most often found on south-facing slopes.
False. They are usually north- or north-east-facing, because these shaded slopes kept snow and ice longest.
What is an arête and how does it form?
A narrow, steep-sided knife-edge ridge, formed where two corries erode back to back.
What is a pyramidal peak and how does it form?
A sharp, pointed mountain summit, formed where three or more corries erode back to back around a mountain.
What is a glacial trough and how does it form?
A straight, steep-sided, flat-floored U-shaped valley, formed where a glacier widened and deepened a former V-shaped river valley by abrasion and plucking.
What is a truncated spur and how does it form?
A steep, blunt-ended cliff on a valley side, formed where the glacier cut off (truncated) the ends of interlocking spurs that stuck into the valley.
Give two characteristics of a ribbon lake.
It is long and relatively narrow, and it occupies the floor of a glacial trough.
How does a ribbon lake form?
The glacier eroded a deeper hollow where the rock was softer (or a moraine dammed the valley), and the hollow later filled with water.
What is a hanging valley and how does it form?
A smaller tributary valley left high above the main glacial trough, because the tributary glacier was smaller and eroded less deeply; a waterfall often drops from it.
What is an erratic?
A large boulder transported by ice and deposited in an area of a different rock type.
Describe the shape of a drumlin.
An elongated, egg-shaped or oval low rounded hill of till, with one side steeper than the other.
On a drumlin, which end shows the direction the ice came from?
The steeper, blunter end faces the direction the ice came from; the gently tapering end points the way the ice was moving.
What is lateral moraine?
A ridge of material along the sides of a glacier, built up from freeze-thaw debris falling from the valley sides onto the ice edges.
What is medial moraine?
A line of material running down the middle of a glacier, formed when two glaciers merge and their lateral moraines join.
What is terminal moraine?
A ridge of till deposited across the valley at the furthest point the glacier snout reached.
Give two pieces of evidence on an OS map or photograph that an upland area was glaciated.
A long narrow ribbon lake, and a steep-sided glacial trough with a flat valley floor. (Also moraine/till deposits or corries with tarns.)
Name one landform of erosion and one of deposition found in Snowdonia.
Erosion: the corrie Cwm Idwal (or the ribbon lake Llyn Ogwen). Deposition: moraine ridges on the floor of the Ogwen valley.