Formation
Sandar are found in glaciated areas, such as Svalbard, Kerguelen Islands, and Iceland. Glaciers and icecaps contain large amounts of silt and sediment, picked up as they erode the underlying rocks when they move slowly downhill, and at the snout of the glacier, meltwater can carry this sediment away from the glacier and deposit it on a broad plain. The material in the outwash plain is often size-sorted by the water runoff of the melting glacier with the finest materials, like silt, being the most distantly re-deposited, whereas larger boulders are the closest to the original terminus of the glacier.
An outwash plain might contain surfacial braided stream complexes that rework the original deposits. They may also contain kettle lakes, locations where blocks of ice have melted, leaving a depression that fills with water. The flow pattern of glacial rivers across sandar is typically diffuse and unchannelized, but in situations where the glacial snout has retreated from the terminal moraine, the flow is more channelized.
Sandar are most common in Iceland, where geothermal activity beneath ice caps speeds up the deposition of sediment by meltwater. As well as regular geothermal activity, volcanic activity gives rise to large glacial bursts several times a century, which carry down large volumes of sediment.
The Gaspé Peninsula that makes up the essential part of southern Quebec (Lower St-Lawrence and Gaspé areas) also contains several example of paleo-sandar, dating from the Pleistocene ice melt.
Read more about this topic: Outwash Plain
Famous quotes containing the word formation:
“Out of my discomforts, which were small enough, grew one thing for which I have all my life been gratefulthe formation of fixed habits of work.”
—Elizabeth Stuart Phelps (18441911)
“The moral virtues, then, are produced in us neither by nature nor against nature. Nature, indeed, prepares in us the ground for their reception, but their complete formation is the product of habit.”
—Aristotle (384322 B.C.)
“... the mass migrations now habitual in our nation are disastrous to the family and to the formation of individual character. It is impossible to create a stable society if something like a third of our people are constantly moving about. We cannot grow fine human beings, any more than we can grow fine trees, if they are constantly torn up by the roots and transplanted ...”
—Agnes E. Meyer (18871970)