SURFICIAL GEOLOGY of the
Catskill Mountain Region
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The majority of the surficial geology of the Catskills was determined during the last 1.6 million years. Four ice ages inundated this area, most recently the Wisconsin advance. The Wisconsin glaciers finished retreating from this area only approximately 14,000 years ago. As seen on this map, the majority of the region is composed of glacial till. Till (material deposited by a glacier) is unstratified, unsorted, and is made up of a wide range of sizes. For this reason, glacial till generally acts as an aquifer, holding large amounts of groundwater. As you can see from this map, the high peak regions are entirely comprised of bedrock. These sandstone and conglomerate mountaintops were scoured and scraped by glaciers moving around and over their summits, leaving virtually no loose material.