There are four main mining methods: underground, open surface (pit), placer, and in-situ mining.

Florida Geological Survey's "Sinkhole Questions":

U.S. Geological Survey Volcano Hazards Program FAQs:

From the U.S. Geological Survey Volcano Hazards Program FAQs:

"Definitely. Many stratovolcanoes have a plumbing system of hot acid water that progressively breaks down hard rock to soft, clay-rich material. The volcano is gradually weakened, and large parts may suddenly fail. Resulting water-rich landslides are especially dangerous because they can occur without any volcanic or seismic warning.

There are many different kinds of hazards associated with volcanic eruptions, depending on the type of volcano and eruption. Some volcanoes typically produce highly explosive eruptions, such as in the subduction zones of Alaska and the Pacific northwest, and others produce  less energetic eruptions, such as in Hawaii. Therefore, hazards detailed below are not necessarily relevant to every volcano.

U.S. Geological Survey:

U.S. Geological Survey Volcano Hazards Program FAQs:

The U.S. Geological Survey maintains statistics about the worldwide supply of metal resources, including copper and precious metals like gold and platinum. The USGS also tracks statistics on non-metal, industrial minerals like sand and crushed stone. The Energy Information Administration maintains data on the trade of energy minerals like coal, natural gas, petroleum, and uranium. 

The U.S. Geological Survey (USGS) maintains statistics about the worldwide supply of approximately 90 mineral commodities, including significant industrial minerals such as sand and gravel.

Drew L. Siler, PhD, Geothermal Geologist: