General Knowledge of Glaciated Landscapes Flashcards
What are ice sheets?
Can be over two miles thick and cover whole continents. They are an example of an unconstrained glacier, where they cover the underlying topography. Like ice caps, they often have valley glaciers coming off the sides and have ice streams moving ice through the sheet. 96% of the world’s ice is found in 2 ice sheets - Antarctica and Greenland.
What are ice caps?
Ice caps cover entire mountainous regions. They are up to 50000km2, any larger than this then they become an ice sheet. For example Vatnajokull in Iceland.
What are piedmont glaciers?
Valley glaciers that have spilled out into lowland regions. A type of unconstrained glacier. For example areas in Antarctica.
What are valley glaciers?
Tongues of ice confined within valleys in mountainous regions. They are an example of a constrained glacier, it’s path and form determined by the landscape. For example the Aletsch Glacier in Switzerland.
What are cirque glaciers?
Small glaciers that occupy a bowl shaped hollow at the head of a glacial valley. An example of a constrained glacier. For example the Lower Curtis Glacier in USA.
How long does diagenesis take?
30-1000 years.
How far down do you have to go to find glacier ice?
100m.
What is the movement of a glacier like?
The movement of glaciers is uneven. Different areas move at different speeds, for example the middle section of the glacier moves faster than the edge sections. This is probably due to the friction caused by the bedrock valley walls.
How does relief affect flow?
As a glacier flows over a steep slope it can’t deform quickly enough and so stretches and fractures forming crevasses. This is known as extending flow. As the gradient of the slope decreases the ice thickens and compresses closing the crevasses. This is known as compressing flow.
Describe the flows of energy in a glacier.
The energy driving the glacial system ultimately originates in the global hydrological cycle from solar energy, as snow falls at altitude and then turns into glacier ice by diagenesis it acquires gravitational potential energy. Once the glacier becomes sufficiently large to flow down the valley the gravitational potential energy is converted to kinetic energy. It is this kinetic energy in the movement of the glacier which erodes bedrock to shape the landscape. Solar energy then melts the glacier ice to produce meltwater which again converts gravitational potential energy into kinetic energy to transport material down the valley in streams to create new landforms. Solar energy also drives physical weathering processes which are important in shaping glacial valleys. In the post-glacial period vegetation converts solar energy into chemical energy by photosynthesis and then into kinetic energy as roots penetrate into bedrock causing biological weathering modifying glacial landforms.
What is accumulation?
The accretion of snow and ice onto a glacier. Occurs at high latitude and altitudes where temperature prevents melting.
What is ablation?
The loss of ice mass due to melting and sublimation (small contribution).
What is a mass balance?
The annual mass balance (budget) of a glacier is the difference between accumulation and ablation over one year.
What is the equilibrium line?
Where accumulation = ablation.
What is a dynamic equilibrium?
Glaciers exist in a state of equilibrium when the inputs are perfectly balanced with outputs. Dynamic equilibrium is the idea of a system adjusting to bring itself back to equilibrium if either the inputs or outputs change and equilibrium is disturbed. It does this through negative feedback loops to counteract the change.
