Points Earned:1/1Correct Answer:BYour Response:B
12.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 other rocks.What made this odd-looking surface?Points Earned:1/113.The two pictures above, I and II, show traces of former life in rocks from the Grand Canyon. Each is “typical”—the rocks near sample I contain fossils similar to those shownin sample I, and the rocks near sample II contain fossils similar to those shown in sample II. It is likely that:
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 algal-mat 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.Points Earned:1/114.Geological evidence based on several radiometric techniques has provided a scientificallywell-accepted age for the Earth. Represent that age of the Earth as the 100-yard length of a football field, and any time interval can be represented as some distance on the field.
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