Ice and Water

Driving west on Route 23 before dropping into the the Hudson River valley proper, one can see last night's snow on the Catskill Mountains, especially in the wind shadows of its peaks. The mountains are very old, remnants of mountain building hundreds of millions of years ago.
As mentioned in Orogeny below, long weathering and three ice ages stripped away the tops down to these remaining mountain roots, which formed the west wall of a great lake created when the last glaciers melted back.
A close look at the far hills shows horizontal lines, the remains of submerged silt terraces revealing successively lower water levels and associated terraces as the great lake drained away in pulses over thousands of years to become the Hudson River Valley today. A similar effect on a smaller scale can be seen in the West's great reservoirs at times of low water.
At the time of that great lake, the modest country home in the foreground would have been hundreds of feet below the surface.