The picture above shows a very hard piece of rock about six inches across,in the Grand Canyon.The surface of the rock looks rather different from the surfaces of many otherrocks.What made this oddlooking surface? A fault, which dropped old rocks so that they were preserved in DeathValleytype valleys and so were not eroded away.A glacier; the high plateaus adjacent to the canyon had iceage glaciers thathelped carve the canyon.
11/1/2018 RockOn #10: GEOSC 10 Fall 2018, Merged 12/15 The river, which blasted the rock with sand and siltladen water during floods;this shows that even hard rocks can be eroded by rivers.The wind, which has been primarily responsible for carrying away sand bars,and which sandblasts rocks with the sand.The river; because the rocks are still there, this shows that rivers cannot reallyerode hard rocks and thus that the river could not have carved the canyon.The Canyon was carved by the Colorado River. Glaciers have notbeen there, and while wind and faults can change the appearance ofrocks, none makes something like this riverpolished rock, as you sawin one of the Grand Canyon VTrips. ! 1 / 113In the two pictures above, I and II, show traces of former life in rocks from theGrand Canyon. Each is "typical";the rocks near sample I contain fossilssimilar to those shown in sample I, and the rocks near sample II containfossils similar to those shown in sample II.It is likely that:!
11/1/2018 RockOn #10: GEOSC 10 Fall 2018, Merged 13/15 Sample I is from high in the cliffs of the Canyon, and sample II is also from high in the cliffs of the Canyon. Sample I is from low in the cliffs, near the river, and sample II is also from low in the cliffs, near the river. Sample I shows the President's desk, and sample II is the sole of the Speaker of the House's shoe. Sample I is from lower, nearer the river, and sample II is from higher in the cliffs of the Grand Canyon. Sample I shows reptile tracks from the fossil sand dunes of the Coconino far up the side of the Canyon, and thus shows the presence of complex creatures. Sample II includes algalmat deposits (stromatolites) from the Precambrian Chuar Group of the Grand Canyon Supergroup, deep in the Canyon near the river, from a time when biology was not a whole lot more diverse than algal mats. 1 / 1
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- Spring '99
- Sedimentary rocks