Natural gas cannot flow out of some shale deposits naturally when the rock has low permeability. In this situation, a method called hydraulic fracturing can be used to extract natural gas. Shale is shattered by pumping fluids (water + chemicals + sand) into the gas-bearing shale unit. The pressure from the incoming fluid fractures the shale, sand grains prop the fractures open as the fluid is then pumped out of the ground, and then the gas can flow freely.

Hydraulic fracturing, also called "fracking," is controversial because:

1. preexisting faults can be reactivated, which can cause small-sized earthquakes;

2. chemicals in the injected fluids can get into groundwater that is used for drinking water; and

3. the wastewater is environmentally hazardous and can leak into soils; etc.

Most of the wastewater produced by fracking is pumped back to the surface where it is stored in artificial ponds. Wastewater is diluted with fresh water and pumped back into the ground to shatter more shale. After several uses, the water can no longer be used and is sent to specialized treatment facilities. This process uses millions of gallons of fresh water each year, often in regions where water availability is already a problem.

Select all statements that apply to the process of hydraulic fracturing, or "fracking."

A). Wastewater from hydraulic fracturing is absorbed into the shale indefinitely.
B). Hydraulic fracturing allows geologists to capture natural gas stored in the pore spaces of shale.
C). Some large magnitude historic earthquakes can be traced to the use of hydraulic fracturing.
D). Hydraulic fracturing threatens the supply of other natural resources.
E). Once the shale is shattered, fractures remain open due to the inherent strength of the shale.