Glaciation Flashcards
How were Glaciers and ice sheets formed?
Snow that fell gradually turned to solid ice, the ice began to move slowly to lowland areas under the influence of gravity as great rivers of ice called glaciers.
Some glaciers melted together, while others joined together to form ice sheets. The ice sheets covered huge areas of the earth’s surface, an ice age had arrived.
What were the warmer periods known as during the ice age?
During the ice age, there were warmer periods known as interglacial periods.
What do glaciers do when they move?
What are the two processes of this?
As a glacier moves, it erodes the landscape by two processes, plucking and abrasion
Explain Plucking
As ice moves, friction happens between the ice and the ground below. This friction creates heat, which causes the ice at the base to melt. The meltwater flows into the cracks in the rock. The water then refreezes around the rocks and sticks to the glacier. When the ice moves forward again, it can pull or pluck chunks of the rock out of the ground.
Explain Abrasion
Plucked rocks become embedded in the base of the glacier. As the glacier moves, the rocks abrade - scrape and smooth - the surface over which they pass.
List the features of glacial erosion
Glaciated valley, cirque, tarn, pyramidal peak, arête, paternoster lakes, truncated spur, hanging valley
What is a glaciated valley?
What is a cirque?
What is a tarn?
What is a pyramidal peak?
Glaciated valley: A V-shaped valley straightened and flattened by the movement of a large glacier to become a U-shaped valley. An example is Glendalough, Co. Wicklow.
Cirque: Also known as a corrie, a large hollow on the side of a mountain. It has 3 sides and is the birthplace of a glacier. An example is The Devil’s Punchbowl, Co. Kerry.
Tarn: A lake inside a cirque. An example is Upper and Lower Lough Bray, Co. Wicklow.
Pyramidal peak: Steep-sided pyramid-shaped mountain that was eroded on all sides by many cirques. Carrantouhill in the Mcgillacuddy Reeks in Co. Kerry is an example.
What is an arête? What are paternoster lakes? What is a truncated spur? What is a hanging valley? Give an example of each
arête: A narrow, steep-sided ridge, usually between two cirques. An example is The Devil’s Punchbowl, Co. Kerry.
paternoster lakes: When a long, narrow lake occupies the floor of a glaciated valley, it is called a ribbon lake. When a few ribbon lakes are linked, they are called paternoster lakes. An example is on Brandon Mountain in Kerry.
truncated spur: Originally an interlocking spur that was eroded, having its ‘head’ cut off as the glacier moved through the valley. An example is in Glendalough Valley in Wicklow.
hanging valley: A small tributary valley that hangs above the main glaciated valley. An example is Poulanass waterfall in Wicklow.
Explain the formation of a glaciated valley (2)
- The base of the glacier melts into the underlying rocks due to the heat caused by friction. Then the meltwater froze again, and as the glacier moved on, it plucked chunks of rock out of the ground.
- Plucked rocks became embedded in the base of the glacier. As the glacier moved, the rocks abraded the rock surface that they passed over.
Explain the formation of a Cirque/Corrie (5)
- Snow collects in a mountain hollow high up in the mountain. With repeated snowfalls, the snow compacts to form ice. A glacier is born.
- Through plucking and abrasion, the hollow grows deeper. Freeze-thaw action is also at work here.
- When the glacier is big enough to flow over the edge of the cirque, it then begins its journey down the valley.
- When the glacier melts, a lake called a tarn may be trapped in the cirque hollow.
- When two cirques form back to back, the ridge is known as an arete.
What is supraglacial?
What is englacial?
What is Subglacial?
Supraglacial: Materials found on the surface of the glacier, along the top or sides. Such material is carried along as the glacier moves. This material has usually fallen down the mountain and landed on the sides or top of the glacier.
Englacial: Any regolith (loose material) trapped within the ice, including material that has fallen down cracks in the ice.
Subglacial: Loose regolith trapped underneath the glacier and dragged along in the bottom of the ice.
What are some features of glacial deposition?
Terminal moraine, drumlin swarm, erratic, esker
What are features of glacial deposition?
The features of glacial deposition are mainly seen in lowland areas. As a glacier moves slowly down the valley to the lowland, it carries eroded material with it. When it melts, it begins to deposit its material, creating features.
What is a moraine and what are the four types of them?
A moraine is a mass of rocks and other material carried down and deposited by a glacier.
- Recessional Moraine: A moraine marking a temporary stop in the retreat (moving back) of a glacier.
- Lateral Moraine: Found at the side of the glacier, made of broken rock and soil that fell down the mountain and gathered at the side. This is supraglacial material.
- terminal Moraine: Found at the front of a glacier, made up of material that is pushed ahead of the glacier. A terminal moraine marks the endpoint of the glacier.
- medial moraine: Found in the middle of a glacier when two glaciers combine. Their two lateral moraines join together. This is englacial material.
What are drumlins and how are they formed? (3)
Drumlins are oval-shaped hills that are made of deposited boulder clay (sand and clay mix). They often occur in large numbers known as swarms.
1. Glacial ice deposits boulder clay in irregular heaps.
2.The ice retreats and then advances again. This time it shapes and smooths the boulder clay into rounded oval-shaped hills.
3. The steep slope of the drumlin is the direction from which the ice advanced. The gentle slope points to the direction in which the ice was travelling.
An example is Clew Bray in co. mayo
