Geology/Dating Mountains
Dating by radioactive isotopes can be a wonderful thing. The rate of disintegration of elements used in dating are, to the best of our knowledge, unaffected by natural processes on earth. That is, earthly levels of temperature, pressure, exposure to light, et cetera, neither speed up nor slow down the rate of transformation of a radioactive element to its daughter substance. Thus the ratio between a parent element and its daughter product plus the knowledge of the rate for a given system tells us the elapsed time.
Among things that can be dated in this manner are cave formations: stalactites and stalagmites. As the formation grows, radioactive materials may be incorporated, isolating the substances from additions or losses. Dating of cave formations in the Guadalupe Mountains, for example, tells us when a particular cave system was elevated above the water table, allowing cave formations to grow. Caves at different elevations allow us to determine the rate at which the mountains were uplifted, and the time at which growth basically ceased, data otherwise difficult to come by.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
