The economies of ghana, sierra, leone, the ivory coast, and other nations depend largely on the export of a. petroleum products b. uranium c. cash crops d. gold

Mantle convection is the process that drives plate tectonics. the theory of plate tectonics states that the crust is divided into plates that float on the semi molten mantle below. the circular motion of the magma as it slowly rises and falls or move though convection cells drags the plates along causing them to move. the heat source in the lamp would represent the earth's core. the core is the source of energy that drives convection in the mantle. the lava represents molten magma under the earth's surface. if the lava lamp had floating pieces they would move as the circular motion of the lava in the lamp as it rises and falls would move them along the surface. these floating pieces would represent pieces of the earth's crust. 

The investiture controversy began as a power struggle between pope gregory vii (1072–85) and henry iv, holy roman emperor (1056–1106).[2] a brief but significant struggle over investiture also occurred between henry i of england and pope paschal ii in the years 1103 to 1107, and the issue played a minor role in the struggles between church and state in france, as well.by undercutting the imperial power established by the salian emperors, the controversy led to nearly 50 years of civil war in germany, and the triumph of the great dukes and abbots. imperial power was finally re-established under the hohenstaufen dynasty. historian norman cantor:

Climate change to earth function human can't reduce climate