The thermal output of the earth melts a thin film of water on the glacier bottom, and the ice slides on that, too. Thrust sheets made of rock also slide on water. The lower part of a glacier is plastic, the upper part brittle-like the earth’s moving plates and the plastic mantle beneath them. Where the brittle glacier surface bends, it cracks into crevasses, into fracture zones, as does the brittle ocean crust (the Clarion Fracture Zone, the Mendocino Fracture Zone). Such fractures are everywhere in the rock of continents, too. In fact, the ridged-and-valleyed surface of almost any flowing glacier is remarkably similar to the kantoor huren per uur eindhoven sinuous topography of the deformed Appalachian mountains. The continental ice sheet moves toward the equator and keeps on going until it cannot stand the heat. At the latitude of New York City, generally speaking, the ice melts as fast as it advances, and thus it goes no farther, and leaves on Staten Island its terminal moraine. Ocean temperatures will have dropped because of the cold, and therefore the oceans are providing less snow to feed the ice. On all fronts, the ice retreats-not necessarily to disappear. The climate warms. The oceans warm. The snow pack thickens in the Great North Woods. A glacier spreads again. Once the pattern is set, the rhythm is relatively steady. For us, the ice is due again in ninety thousand kantoor huren per uur haarlem years.
We ran on through Ohio on the bed of the great former lake, Kelleys Island far behind us. Where there had been sand spits reaching into the water, with sandy hooks at their tips, there were farm buildings standing on the dry spits-the high prime ground, a few feet higher than the surrounding fields. Now, at spring plowing time, these things were visible as they would not be for a year again.