Question

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What activates a convection current, starting the flow of a fluid?

A.
cold temperatures at the north pole

B.
heated liquids at the earth's surface

C.
iron-rich rocks in the mantle

D.
temperature differences in the mantle

Answer 1

@ghuczek

Answer 2

@amistre64

Answer 3

The choices are not very good. It is the temperature differences that initiate the process of convection. Warm fluids (like air or water) become less dense and rise, while the colder ones become more dense and drop. This begins a vertical circulation pattern. The lateral deflections are caused by air being displaced, tidal effects, and in the atmosphere, by the Coriolis Effect.

So, using what I've said, you can rule out choices C and D. Solar energy drives convection at the Earth's surface. See if you can take it from there. I don't like either of the remaining choices, because they both drive convection in the atmosphere and in the Earth's oceans. If choice B were ... heated matter at the Earth's surface, I would jump at that choice. The question is poorly crafted, because one could argue that either A or B are possible answers.

Answer 4

I just thought of something else here ... Choice D could also work, if you are interested in magma circulation in the mantle. What are you studying? Geology or atmospheric science?

Convection currents in the mantle and those in oceans and in the atmosphere are driven by differences in temperature, but solar energy drives those on the Earth's surface.

Answer 5

Hi-- sorry I took so long to answer. I am studying Geology.

Answer 6

A or D

Answer 7

D is for sure

Answer 8

If it's Geology then try D.