During Tuesday’s presidential debate between former President Donald Trump and Vice President Kamala Harris, the topic of fracking as a method of drilling for fossil fuels was a heated discussion, with Harris’ positions on the issue coming under scrutiny.

While Trump has repeatedly called for all possible tactics to increase drilling and production capacity in the United States, Harris’ stance on fracking in particular has been called into question. These concerns can be traced back to her 2020 presidential campaign.

The situation is explained below.

What is fracking?

Fracking, also known as hydraulic fracturing, involves breaking apart shale rock formations using pressurized fluid containing water and other chemicals.

According to the BBC, these cracks allow fossil fuels such as natural gas and oil to flow more freely.

Has Harris’ position on fracking changed?

During the 2020 presidential campaign, Harris said several times that she would support banning the practice to address issues related to climate change.

“There’s no question that I support a ban on fracking and that we need to start doing what we can do on public lands on day one,” she told CNN at a 2019 climate change meeting.

Her stance on the issue has changed over the next five years. During an interview with CNN’s Dana Bash, she discussed the reasons behind changes in her policy positions, and on the topic of fracking, she emphasized that she voted to extend fracking leases when she was vice president.

Trump lashed out at Harris for her about-face on the issue.

“She has at least 12 and probably 14 or 15 different policies listed,” he said.

Why is fracking so controversial?

According to the BBC and other publications, fracking can cause vibrations in the Earth’s surface. In addition, the practice uses huge amounts of water, which must be transported to the site of use.

According to Yale researchers, the process also produces a huge amount of wastewater and releases greenhouse gases, such as methane, into the atmosphere. The release of chemicals poses health risks.

Proponents of fracking say the U.S. should use the technology to increase production of oil and other fossil fuels and become less dependent on other countries. Groups like the American Petroleum Institute point to thousands of jobs directly or indirectly linked to the energy sector that depend on technologies like fracking.