Describe the Younger Dryas period, the evidence for its existence, and the hypothesis for its origin
What will be an ideal response?
The Younger Dryas is a 1300-year-long cold snap that started about 13,000 years ago and interrupted the overall trend of warming after the peak of the last ice age. Evidence for the Younger Dryas includes changes in temperature-sensitive vegetation in successive layers of sediment, proxy measurements of ocean temperature, and proxy measurements of air temperature over Greenland. The most widely held hypothesis for the Younger Dryas points to a period without conveyor-belt-style ocean circulation in the North Atlantic Ocean, which decreased the efficiency of ocean currents to distribute heat away from the equator to higher latitudes. The conveyor-belt circulation may have temporarily ceased when large volumes of freshwater from the melting of ice-age glaciers decreased the salinity of surface water in the North Atlantic so that the sinking part of the conveyor belt could not exist.
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Glacial till is:
a. any sediment deposited as a result of glacial activity. b. boulders transported long distances and deposited by glaciers. c. an elongated, spoon-shaped hill that has been shaped by an overriding glacier. d. unstratified sediment deposited directly by a glacier. e. a lake within an outwash plain.
Volcanic activity generally does NOT occur
A) along sea-floor spreading centers. B) in association with plutons. C) along subduction boundaries. D) in association with hot spots over plumes in the mantle.
In terms of running the Earth's atmospheric processes, significant energy comes from the Sun and ________
A) the Moon B) the next closest star C) the reflection from Venus D) the Earth's interior E) no other source
All of the following large-fish fisheries are being over fished except
A. marlin. B. albacore tuna. C. yellowfin tuna. D. bluefin tuna.