photo (50 ft): second-year ice under pressure; numerous ridges; snow (Environment Canada)
Where the ice is subjected to pressure its surface becomes deformed. In New ice and Young
ice this may result in rafting as one ice floe over-rides its neighbour; in thicker ice it directs to
the formation of Ridges and Hummocks according
to the pattern of the convergent forces
causing the pressure. During the process of ridging and hummocking, when pieces of ice are
piled up above the general ice level, large quantities of ice are also forced downward to
support the weight of the ice in the ridge or hummock. The draught of a ridge can be three to
five times as great as its height and these deformations are thus major impediments to
navigation. Freshly formed ridges are normally less difficult to navigate than older Weathered
and consolidated ridges.
