This shore lead is constantly opening and shutting; opening when there are offshore winds, or spring ebb-tides, crushing shut when there are northerly winds or spring flood-tides.

Here the ice is smashed into fragments of all sizes and piled up into great pressure ridges parallel with the shore.
The ice is smashed into these pressure ridges by the sheer and unimaginable force with which the floes are driven against the edge of the glacial fringe, just as farther out the pressure ridges are caused by the force with which the great floes themselves are crushed and smashed together by the force of the wind and the tides.
These pressure ridges may be anywhere from a few feet to a few rods in height; they may be anywhere from a few rods to a quarter of a mile in width; the individual masses of ice of which they are composed may vary, respectively, from the size of a billiard ball to the size of a small house.
Going over these pressure ridges one must pick his trail as best he can, often hacking his way with pickaxes, encouraging the dogs by whip and voice to follow the leader, lifting the five-hundred-pound loaded sledges over hummocks and up acclivities whose difficulties sometimes seem likely to tear the muscles from one's shoulder-blades.
Between the pressure ridges are the old floes, more or less level.

These floes, contrary to wide-spread and erroneous ideas, are not formed by direct freezing of the water of the Arctic Ocean.

They are made up of great sheets of ice broken off from the glacial fringe of Grant Land and Greenland, and regions to the westward, which have drifted out into the polar sea.

These fields of ice are anywhere from less than twenty to more than one hundred feet in thickness, and they are of all shapes and sizes.