Landforms of glaciofluvial deposition - Varves Flashcards
What is a varve?
A varve is a pair of thin layers of clay and sand of contrasting colour and texture which represent the deposit of a single year (summer and winter) in a lake.
In the past, where did proglacial lakes develop?
In the past, proglacial lakes developed in locations where glacial meltwater occupied depressions at the ice front and the water was unable to drain away.
Why did meltwater streams have more energy to transport larger particles, such as sands, away from the glacier into surrounding lakes in the warmer months of spring and summer?
During the warmer months of spring and summer, the amount of melting would have increased. Therefore, meltwater streams had more energy to transport larger particles, such as sands, away from the glacier into surrounding lakes.
Why was only smaller amounts of finer material carried into the lake in the autumn?
In the autumn, there would have been less water from melting and so the streams would not have been able to transport as much load. Smaller amounts of finer material would thus have been carried into the lake.
Where would the lightest and finest sediments finally settle in the late autumn and winter?
The lightest and finest sediments would finally settle on the lake bed in late autumn and winter as a result of the low energy environment.
Explain how varves are the result of differing rates of transportation in the summer and the winter?
A series of layers are built up: coarser, sandy deposits in the summer followed by finer, clay deposits in the winter.
