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geosc5 - 1 Chemical weathering of a continental rock such...

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1. Chemical weathering of a continental rock such as granite in a climate such as that of Pennsylvania produces: A. Feldspar and dark-mineral grains, that do not wash away easily, and dissolved quartz that does wash away easily B. Clays that dissolve and wash away easily C. Clays and rust, that do not wash away easily, and soluble ions, that do wash away easily D. Soluble ions that do not wash away easily, and clays and rust that wash away easily E. Salt-laden soils (also called pedocals) Weathering of granite in Pennsylvania makes some things (clay, rust, and quartz sand) that stay behind to contribute to soil, and other things (soluble ions) that dissolve and wash away very quickly. In dry climates, not very much rainwater percolates downward and through rocks to streams; most rain soaks in a little bit, but is evaporated back to the atmosphere before soaking way down in soil. Very soluble things (sodium ions, for example) may wash away in the little water that reaches streams, but slightly less soluble things (which would wash away in Pennsylvania) such as calcium will be released from rocks but then accumulate in spaces in the soil as water evaporates. These give rise to pedocals, calcium-laden soils. But these are not expected in rainy Pennsylvania, and this isn’t a subject introduced in the course, so you really shouldn’t worry about it. Points Earned: 1/1 Correct Answer: C Your Response: C 2. Calcium released by chemical weathering is transported by streams to the ocean, where much of it: A. Is used by clams, corals, etc. to make their shells B. Builds up in the water, making the ocean saltier C. Evaporates from the ocean and rains back out on the land
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D. Is subducted back into the mantle at the mid- ocean ridges E. Is extracted from the water by marine dairy cows to add to milk Most common shells seen at the beach are calcium carbonate, and the calcium is provided by weathering of rocks on land. Calcium ions do not evaporate easily, and are not very common in the atmosphere. A little bit of sea salt, and anything else small in the sea, does escape in spray (stand by the sea on a windy day and you’ll get spots on your sunglasses), but most of the calcium reaching the sea is used there. The “saltiness” of the ocean is a quite different chemical, not calcium. Some shells are subducted, many more are scraped off downgoing slabs at subduction zones, but subduction does not occur at mid-ocean ridges, which is where sea floor is made, not where sea floor is consumed. Calcium in milk is a good thing, and helps build strong bones and teeth, but dairy cows rarely go to the beach to go swimming, and wouldn’t enjoy drinking the water to get their calcium. There is a little bit of calcium in grasses, and cows get some of their calcium from there.
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