One billion years ago, in the Precambrian period, the Grenville orogeny (the name for a mountain-building event) was a major force in this area. This event turned the rocks into the gneisses (sedimentary rock that has been subjected to great heat and pressure and has metamorphosed into a very hard rock) and granites that we see today, in the Hudson Highlands. The only other New York sites for this ancient rock, which has successfully resisted erosion, are in the Adirondacks. The Taconic orogeny, 450 million years ago created rock that is brittle, mostly sedimentary shale.

Two more orogenies, the Acadian, 410 to 380 million years ago, and the Alleghanian, 320-280 million years ago continued to shape the building of the continent.

Between 250 million and 235 million years ago, the supercontinent Pangaea began splitting apart. It was during this period of land splitting apart, in the Mesozoic, that the Palisades were formed and it left a gap the Hudson would eventually fill.

26,000 - 13,000 years ago the Hudson Fjord is created by the Wisconsin Stage of the last Glacial age.

The White Mountains of New Hampshire-
Southern Appalachians