Why are there lines, otherwise known as layers, in the walls of the Grand Canyon?

Jafato

The Colorado River has carved the Grand Canyon into four plateaus of the Colorado Plateau Province. The Province is a large area in the Southwest characterized by nearly-horizontal sedimentary rocks lifted 5,000 to 13,000 feet above sea level. The Plateau’s arid climate produced many striking erosional forms, culminating in the Grand Canyon. The Canyon’s mile-high walls display a largely undisturbed cross section of the Earth’s crust extending back some two billion years. Three “Granite Gorges” expose crystalline rocks formed during the early-to-middle Proterozoic Era (late Precambrian). Originally deposited as sediments and lava flows, these rocks were intensely metamorphosed about 1,750 million years ago. Magma rose into the rocks, cooling and crystallizing into granite, and welding the region to the North American continent. http://digital-desert.com/grand-canyon/natural.html Nov 18 08, 5:51 AM

deepakmr

The layers were formed by the Colorado river and it's tributaries over millions of years. http://en.wikipedia.org/wiki/Geology_of_the_Grand_Canyon_area http://www.bobspixels.com/kaibab.org/geology/gc_geol.htm Nov 18 08, 5:55 AM

queproblema

Geologists' interpretations of the evidence varies widely. The above answers are the most generally accepted. Others propose models based on catastrophe rather than gradual erosion or build-up. This link is from a fundamentalist Christian site that is determined to prove correct its model of a young (less than 10,000 yrs. old) earth: http://www.icr.org/research/index/researchp_sa_r02/ This one is from a Christian site that believes astronomy proves the earth must be billions of years old: http://www.answersincreation.org/rebuttal/icr/drjohn/drjohn_156.htm Interestingly, even such a hard-core evolutionist and atheist as Carl Sagan repeatedly presents in his grand work for the layman, "Cosmos," the explosions and collisions he believed account for the formation of the Universe and the origins of life. "Some fifteen billion years ago our universe began with the mightiest explosion of all time." http://www.cooperativeindividualism.org/sagan_cosmos_who_speaks_for_earth.html interpretations vary :-( Nov 18 08, 7:19 PM