Note the two sets of crevasses near the beginning of the Athabasca Glacier (on the Athabasca and Saskatchewan air photo set). How do crevasses form? (Choose the best answer)
a.they are formed in the rigid/brittle upper layer of glaciers, where ice is not able to deform plastically and therefore breaks/fractures when subjected to tensional forces
b.they are formed when two cirques on either side of a ridge erode into each other by plucking, creating a low point in the ridge
c.they are formed when two separate glaciers come together and combine into one, but do not combine perfectly, causing cracks in the new glacier
