The fact that volcanic rock has often been found early in the rock record but less frequently in later rock layers suggest to scientists the following conclusion about early earth: <span>volcanic activity was more common in the past than it is today.
</span>Besides volcanic activity in general, also huge volcanic eruptions<span> were much </span>more common than today<span>.</span>
Answer: Mining and quarrying can be very destructive to the environment. They have a direct impact on the countryside by leaving pits and heaps of waste material. The extraction processes can also contaminate air and water with sulfur dioxide and other pollutants, putting wildlife and local populations at risk.
. Be international
. Consider multiple viewpoints
. Deal with multiple uses for resources
The entire United States and the rest of the world serve as the hinterland for all of the following cities except Tucson.
