The mountains originally were considerably higher than the present ones as erosion has stripped off the upper parts and deposited this material in the intervening flats, reducing the relief. Most of this erosion took place in Permian time (some 250 million years ago) and produced extensive gravel deposits. Remnants of these gravels may be seen north of Crater Lake, north of Lake Elmer Thomas, east and south of Lost Lake, and in several other parts of the Refuge. Granite is the dominant rock of the refuge, and the gravels formed by erosion are mainly composed of granite fragments. There are unconsolidated well-rounded boulders 6 to 18 inches in diameter, known as cobblestones, surrounded by yellow-to-brown clay. Below the weathered surface they are well cemented. The main geologic event that has taken place since is the erosion of most of the Permian gravels which once covered this area. In recent times, some newer gravels have been deposited along the small streams and in the flats. These can be seen around Lake Lawtonka, along Sandy Creek, Wolf Creek, and in other areas of the refuge. Boulder slides in the drainage depressions are common on many of the steep slopes. One of the best examples of boulder accumulation is the "River of Boulders" on the south side of Mt. Scott. This information is an excerpt from the C.A. Merrit, School of Geology, University of Oklahoma and the Programs in Geosciences at the University of Texas at Dallas.
Previous | Page 1 of 5 | Next
Follow Us Online
Their songs are derived from a large syllable repertoire, an order of magnitude greater than that of other vireos.