When mantle rocks near the radioactive core are heated, they become less dense than the cooler, upper mantle rocks. These warmer rocks rise, while the cooler rocks sink. This movement of warmer and cooler mantle rocks creates pockets of circulation within the mantle called _, which are thought to be the force behind the movement of tectonic plates over the asthenosphere.

d

Explanation:

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a is your answer!

world war i had a devastating effect on german-americans and their cultural heritage. up until that point   german-americans, as a group, had been spared much of the discrimination, abuse, rejection, collective mistrust experienced by so many different racial and ethnic groups in the history of the united states. indeed, over the years, they had been viewed as a well integrated and esteemed part of american society. all of this change with the outbreak of war.