Discuss the origin of Earth’s earliest granitic crust. What processes were important in forming this crust?c What will be an ideal response?
The accretion of island arcs formed the first continental cores. Partial melting of basaltic
oceanic crust yields an intermediate andesitic island arc. The continued partial melting of
andesitic rocks of these island arcs can result in granitic magmas. During Earth’s early
history, the rate of plate tectonics was probably faster, encouraging this process.
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Alkaloid salts are not very soluble in the organic solvent diethyl ether. What might happen to the free-base form of caffeine dissolved in diethyl ether if gaseous hydrogen chloride, HCl, were bubbled into the solution?
A. A second layer of water would form. B. Nothing, and the HCl gas would merely bubble out of solution. C. The acid/base reaction would release heat, which would cause the diethyl ether to start evaporating. D. The diethyl ether insoluble caffeine salt would form as a white precipitate.
Marine animals are unable to break down water molecules to acquire oxygen, but marine plants can
produce enough carbon dioxide to support its own metabolism. Indicate whether the statement is true or false.
Today, Antarctic ice shelves are ________
A) tiny B) gone C) disintegrating D) bigger than in Pleistocene time E) extending close to South America
An active galactic nucleus
A) is a place of intense star formation. B) arises from the gigantic black hole at the center of a galaxy. C) is a supermassive supergiant star that resides at the center of larger galaxies. D) is a giant dust cloud at the center of a galaxy.