What is another name for the circum-pacific belt?
a. pacific ring of fire
b. mediterranean belt
c. mount pinatubo
d. mount vesuvius

The famous Ring of Fire, that consists of basically the entire Pacific oceangoing along California, up over Alaska and Russia, and then back down, along Japan.  More of a horseshoe than a ring, reallybut that's nitpicking. 80-90% of the earth's earthquakes and volcanic activity take place along this ringhence the name.

Geothermic gradient is the rate of increasing temperature with respect to increasing the depth in the earths interior. away from tech tonic plates boundaries, it is about 25-40 c/km (72-87 degrees f/mi) of depth near the surface in most of the world.