Why will Africa have the greatest population growth in the next few years

What does the word submerged mean in the following sentence? after it rained for three days in a row, the streets were completely submerged.

Stone mountain was formed during the formation of the blue ridge mountains around 300-350 million years ago and is considered part of the appalachian mountains. it formed as a result of the upwelling of magma from within the earth's crust. this upwelling, or solidified to form the that became stone mountain.

Witch of the following volcano hazards is made up of rocky particles about the size of a grain of sand