Why might a major volcanic eruption lead to cooler temperatures of earth's surface?

Read these sentences from the text. near the equator, the tropics receive the most rain on a consistent basis. as a result, the fresh water falling into the ocean decrease the salinity of the surface water in that region. [. .] . . as the salt content of sea water increases, so does its density. what can you infer about how rain affects the density of surface water near the equator?

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In chile, the deepest earthquake occurred at 61.7°w longitude at a depth of 540 km. if the rocks at the focus began subducting 10 million years ago and are now 1000 km from their original position, what is the average rate of subduction in cm/yr?