Discuss the mechanisms for the formation the first crust on Earth. What will be an ideal response?
The first crust was probably thin and made of mafic rock. Weathering of mafic rocks of island
arcs yielded sediments richer in silica, and some of the magma in the arc also became richer in
silica. Collisions between island arcs eventually formed a few continental cores as silica-rich
materials were metamorphosed. Larger groups of merged island arcs grew faster by accretion.
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What is the ratio of the percentage of gasoline consumed in the U.S. (compared to rest of the world) to the U.S. percentage of the world's population? In other words, take the worldwide % of gas consumed by the U.S. and divide it by the U.S. share (%) of the world's population.
A. ~10:1 B. ~1:1 C. ~5:1 D. ~2:1
A ridge on an upper-air isobaric chart indicates ____
A) higher-than-average heights B) lower-than-average heights C) average heights D) a region with calm winds
Important astronomical forces affecting Earth include all of the following except
A. the Earth is occasionally impacted by comets and meteorites. B. the Sun radiates energy which warms our planet and drives global climate. C. volcanoes produce the Earth's oceans. D. the Moon's gravitational field produces tide currents which carry nutrients.
Which of the following is true about groundwater mining?
A. Water levels in an aquifer never change. B. It is reversible. C. Water levels in an aquifer get progressively lower over time. D. Water levels in an aquifer are recharged during wet seasons.