The region of the Northern San Juan Mountains is a geologist’s dream. In addition to the wealth of gold, silver, copper, lead and zinc mined out of this area over the past 130 years, there are a myriad of rock formations, some that date back more than 1.5 billion years ago to Precambrian times. Thirty miles north of the park, the awe-inspiring Black Canyon of the Gunnison has carved out a deep, narrow canyon through hard schist, gneiss and granite formations. At its deepest point at Painted Wall, the gorge is 2,300 feet deep (nearly twice as high as the Empire State Building).
In more recent geological times fire and ice created the spectacular San Juan Mountains to the south of Ridgway State Park. Volcanic fury produced a thick layer of igneous rock over 35 million years ago. Then, nearly 5 million years ago the time of the volcanoes ended and the ice ages began. Huge glaciers covered the San Juans and acted like giant bulldozers scouring the mountains to carve breathtaking valleys and peaks, including majestic Mount Sneffels (elevation 14,150 feet).
Here at Ridgway State Park we also have a wealth of geological treasures that predate the volcanic period. Upper Jurassic sandstones of the Morrison, Entrada and Wanakah formations laid down over 150 million years ago are present along both sides of the Uncompahgre Valley, as are exposures of Upper Cretaceous Dakota sandstone dating back 100 million years. Lower Cretaceous sedimentary rocks from 145 million years ago are exposed on the western side of the valley, particularly the Burro Canyon Formation sandstone and claystone. Along the eastern park boundary are deposits of Upper Cretaceous Mancos shale from over 65 million years ago that are highly alkaline calcareous rocks.
The park contains an excellent example of the Morrison Formation, the most renowned dinosaur bearing geologic formation in the world. The Morrison Formation, deposited 145-155 million years ago, is of great paleontological importance with an extensive fossil record of vertebrates, invertebrates, plants and trace fossils.