Pressure ridges
October 25, 1915; Heavy pressure-ridges were forming in all directions....The pack within our range of vision was being subjected to enormous compression, such as might be caused by cyclonic winds, opposing ocean currents, or constriction in a channel of some description. The pressure-ridges, massive and threatening, testified to the overwhelming nature of the forces that were at work. Huge blocks of ice, weighing many tons, were lifted into the air and tossed aside as other masses rose beneath them. We were helpless intruders in a strange world, our lives dependent upon the play of grim elementary forces that made a mock of our puny efforts. Ernest Shackleton, South Ernest Shackleton standing in pressure ridges January 3, 1911: The land of Black (or White?) Island could be seen distinctly behind, topping the huge lines of pressure ridges. Robert Falcon Scott Journals: Captain Sco...