7.Large rivers sometimes have natural levees because: A.Point bars run together to make levees.B.The mud deposited by the river compacts and sinks.C.Water slows and deposits as it leaves the main river channel during floods.D.There are no natural levees.E.Oxbow lakes run together to make levees.The initial slowdown as water spreads into the trees deposits sediment to form natural levees. Sinking mud doesn’t make ridges. Point bars are the sand bars on the insides of meander curves, and oxbow lakes are abandoned meander curves, but neither makes the natural levees that are observed.Points Earned:1/1Correct Answer:CYour Response:C8.Geologically speaking, the water table:
As trees suck up water during droughts, air enters spaces where water once was, so the water table (which is the bottom of the region with some air in spaces) must sink in elevation. Creeks do change inelevation between rain and drought (floods happen…), and while there are random elements in the world, this is surely not one of them. (Whenever someone claims something is random, at least suspect that the person is really saying “I don’t know what I’m talking about, and I’m too lazy to find out.”) And we have not seen the water table in Kern Commons; that would be a really nasty flood!Points Earned:1/1Correct Answer:CYour Response:C 9.Given what you were told in class and the textbook about the formation of caves, it is likely that most large caves are formed: Caves require easily dissolved rock, and water to dissolve that rock. In really dry climates, limestone isa resistant rock that stands in huge cliffs. In wet climates, limestone dissolves to yield caves. Sandstone is not a good cave-former because sandstone does not dissolve easily. (Yes, there are very shallow rock-shelter caves in sandstone, which is why the question specifically notes “large caves”.) And while Diet Pepsi actually would be marvelous at dissolving limestone, Diet Pepsi attacks granite rather slowly and won’t make caves well.
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- Fall '08
- Earthquakes, rocks, Outer core, Death Valley