Fracking, the latest craze in the quest to produce oil and gas, has been blamed for environmental problems ranging from flammable tap water to minor earthquakes. Now a new risk is emerging: sand mining.

To squeeze hydrocarbons out of shale through hydraulic fracturing of the rock -- the process known as fracking -- producers need to pump an enormous amount of sand and other materials into the ground.

Obtaining the sand for this requires removing the top layer of earth over a sandstone deposit and using heavy equipment and large amounts of water to produce the fine grains.