Continental crust is formed by ________
A) recycling of material in giant lava lakes in the early earth history
B) plumes of hot igneous material that rise from the core-mantle boundary to form hot spots
C) partial melting of mantle rocks
D) melting and differentiation of oceanic crust at subduction zones
E) the original planetary accretion that also led to the formation of the earth's other layers
C
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Arctic air masses
A) have about the same temperature characteristics as cP air masses. B) are typically several kilometers thick. C) frequently blanket much of the eastern United States in winter. D) produce little precipitation. E) do not affect North America.
Which of the following ecosystems has the highest average net primary productivity?
A) Algae beds and coral reefs B) Estuaries C) Freshwater swamp and marsh D) Open Ocean E) Upwelling zone
Advection fog:
A) is responsible for the Tule fog of the Central Valley of California. B) occurs when warm air passes over a cool surface. C) rarely travels more than 100 meters from its point of origin. D) is the result of adiabatic cooling.
When it appears that it is no longer profitable to continue fishing as a result of overfishing, the fish populations are said to be ____ extinct.
A. locally B. commercially C. economically D. biologically E. ecologically