Hydraulic fracturing receives much press and is taking place in many parts of the United States. Just a quick review: Fracking is a process of drilling into the earth, then injecting a high-pressure water mixture into the rock to release the gas inside. The water mixture includes sand and chemicals. The gas then flows to the well's head.

Several issues tend to be noted regarding fracking. These include its water use, the earthquake increase in a number of areas in which fracking has taken place, and whether or not alternative industries should be favored for energy production.

The U.S. Geological Survey in 2015 published this map of human-induced earthquakes, after noting that the common fracking-related practice of injecting dirty water back into the earth, and some other industrial uses, had caused earthquakes in eight states.

This is a map of "shale play" locations, or places where fracking or other means of extraction of gas from under shale layers could possibly take place, with the exception of states that have outlawed fracking.

Nature World News has widely covered fracking. In a recent piece, we talked about a Duke University study that found that fracking does not use more water than other energy-extraction methods. However, the study also notes that the scientists remain concerned by the fact that fracking leaves its waste water in a toxic state.

On that note, in fall 2014, the American Chemical Society published a study noting that water released by fracking was still toxic after having been treated.

In spring 2015, a study published by the University of Montana pointed out that landscapes in which oil and gas extraction takes place are forever changed in many cases.

In fall 2014, a group of Stanford University scientists published a study about the pros and cons of fracking. One of them, environmental scientist Robert Jackson, said: "Society is certain to extract more gas and oil due to fracking. The key is to reduce the environmental costs as much as possible, while making the most of the environmental benefits."