City - Sechelt State - BRITISH COLUMBIA Country - Canada
About
The southwest coast of British Columbia, Canada, was formed glacially, with boulders pushed in front of south-moving glaciers over and over through millenia. These residual boulders eventually break down when subjected to freeze-and-thaw cycles over centuries. Here is the evidence, in a textural and compositional smorgasbord.
This process is also called frost shattering. These boulders are quite often called radicals, because of the distinct difference in rock composition compared to the other specimens in the area. The rock breaks down, because water infiltrates the small cracks of the rock and then freezes. When water freezes, it expands by roughly 8 percent. To better understand what is happening, imagine driving a wedge into a piece of wood. :) This particular type of rock looks like granite, or some type of volcanic deposit. Further evidence of this process is the presence of scree or a talus slope. Talus, or scree, is a fairly large pile of loose wedge shaped rock of the same material as the rock undergoing erosion present all the way around the deposit. This process can also occur in desert regions, because it has a large diurnal temperature range, which results in the expansion contraction of the rock.
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