The Science Behind Sinkholes and Their Geological Impact

Randall Orndorff from the U.S. Geological Survey discusses sinkholes, focusing on their occurrence in karst terrains, which are areas with soluble rocks like limestone. He explains how rainwater dissolves these rocks over time, leading to underground voids and potential collapses. The video also covers man-induced sinkholes due to urban infrastructure and the importance of geologic maps in assessing sinkhole risks.

Who is the speaker in the video and what is his profession?

• Randall Orndorff, a geologist with the U.S. Geological Survey

• Michael Johnson, an engineer with the Department of Transportation

• John Doe, a meteorologist with the National Weather Service

• Jane Smith, a biologist with the Environmental Protection Agency

What are karst terrains primarily composed of?

• Metamorphic rocks

• Non-soluble rocks like granite

• Soluble rocks like limestone, gypsum, and salt

• Igneous rocks

What percentage of the United States is underlain by karst terrain?

• 10%

• 20%

• 40%

• 30%

Which state is almost entirely underlain by limestone?

• New York

• Florida

• Texas

• California

What are man-induced sinkholes often caused by?

• Natural erosion

• Earthquakes

• Urban infrastructure like pipelines and sewer lines

• Volcanic activity

What happens when cracks develop in aging sewer lines and water mains?

• They improve water flow

• They lead to soil leaking into the voids, causing collapse

• They cause flooding

• They have no significant effect

What tool does the U.S. Geological Survey use to understand where sinkholes occur?

• Weather maps

• Seismic activity charts

• Geologic maps

• Satellite images

Why is it important to map the geology of an area?

• To find oil reserves

• To determine where soluble rocks are located and assess sinkhole risk

• To predict weather patterns

• To locate mineral deposits

Where can you find more information on sinkholes and geologic maps?

• NASA.gov

• USGS.gov

• Weather.com

• EPA.gov