Question 7 Answer saved Points out of 1.00 Which is TRUE about clastic rocks? Se

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Question 7 Answer saved Points out of 1.00 Which is TRUE about clastic rocks? Select one: a. They are formed by lithification O b. They include evaporates O c. They are classified by composition O d. They form from crystallization of ions in solution Flag question e. They may form by partial decomposition of biologic material Question 8 Not yet answered Points out of 1.00 The presence or arkosic sandstone indicates Select one: O a weathering of feldspar to clays in wet environment O b. presence of aluminum or iron oxides Flag question c. strong chemical weathering such that only the most stable minerals remain (quartz) d. arid climate or rapid erosion e. cold environment with dominant physical weathering Question 9 Which erosive medium is responsible for moving the most material and can carry ALL clast sizes? Not yet answered Select one: Points out of 1.00 a. gravity b. water c. wind d. ice P Flag question

Explanation / Answer

1)They are classified by composition

Clastic sediments or sedimentary rocks are classified based on grain size, clast and cementing material (matrix) composition, and texture. The classification factors are often useful in determining a sample's environment of deposition.

2)arid climate or rapid erosion

The geological significance of arkose has been much debated. Under normal conditions, most of the feldspar decomposes and is converted to clay minerals during weathering of the source rocks, whereas under conditions of extreme dryness or low temperatures, decomposition of the feldspar is inhibited or greatly retarded. Arkoses were, therefore, presumed to be derived from the erosion of a granitic terrane characterized by an arid or glacial climate. Now, however, it is known that the feldspar may escape destruction and thus be transported and deposited with quartz sands if rates of uplift, erosion, and deposition are great enough. Under such conditions, irrespective of the climate, weathering processes are incomplete and the sands derived from such terrane are high in feldspar content. Arkoses, therefore, may be said to indicate either a climatic extreme or high relief. Most ancient arkose deposits seem to be the product of high relief.

3)wind

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