AboutDr Thomas Bell Expertise I can answer questions regarding surface earth processes and the chemical transformations that sediments and rocks undergo with burial. I can also answer questions regarding deep time, the evolution of the elements, and the last 4.5 billion years of earth history. I specialize in metallic ore forming processes, the major geologic time periods when they were produced and what they tell us about the evolution of our planet. Learn more about my professional interests at Stratamodel.com.
Experience I am a professional consulting geologist with a background in the petroleum, mining, environmental, and geotechnical industries with over 25 years of experience.
Education/Credentials Ph.D., Geology, University of California at Berkeley, 1984
M.A., Geology, University of California at Berkeley, 1980
B.S., Geology, San Jose State University, 1978
Expert: Dr Thomas Bell Date: 5/22/2008 Subject: Grand canyon strata composition
Question Someone told me that the Grand Canyon, from top to bottom, is composed of
sedimentary rock (limestone and sandstone), but at the base this abruptly
changes to igneous rock (granite and schist) I understood from HS science
that the Canyon was formed both by uplift of the Colorado plateau and by
erosion caused by the Colorado river. What does this mean in terms of its
effect on the strata? It would seem logical that uplift occur suddenly
beforehand. But what really caused this and how did it happen?
Answer Teri,
You have most of the story right and I am glad to see someone was paying attention during HS science class. The strata of the Grand Canyon where solid rock hundreds of millions of years before the Colorado Plateau began it's vertical journey. The area now covered by the Colorado Plateau, an immense area of uplifted crust, is very similar to the Tibetan Plateau. This chunk of crust was elevated by the same plate collision(s) that produced the Rocky Mtns, the Sierra Nevada, and all of the mountain ranges and valleys of the Basin and Range Province in Nevada over the course of the last 35 million years. As the Rockies grew, streams draining the west flank found zones of weakness and relatively lower topography to drain all the way to the Gulf of California cutting a massive canyon right across the Colorado Plateau.
