Earth science

21. magma tends to rise towards earth's surface primarily because
a. water is abundant in magma
b. rocks become less dense when they melt
c. silica is abundant in magma
d. rocks become more dense when they melt

23. the igneous activity in yellow stone national park is associated with what tectonic setting?
a. divergent plate boundary
b. convergent oceanic-oceanic plate boundary
c. intraplate setting
d. convergent oceanic-continental plate boundary

24. earth's rigid outer layer, consisting of the crust and uppermost mantle, is called the

25. the type of plate boundary where plates move apart, resulting in upwelling of material from the mantle to create new seafloor, is referred to as a(n) plate boundary

26. which of the following is the origin of the heat that moves earth's tectonic plates?
a. the formations of earth
b. active volcanoes
c. the sun
d. electromagnetic radiation