Cave Formation: Biogeochemical Cycles

This video segment adapted from NOVA chronicles the discoveries that led to a radical new theory in which living organisms, not just geological processes, play an active role in cave formation.

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Cave Formation: Kane Cave

This video segment adapted from NOVA describes a simple experiment that confirmed the idea that microbes can accelerate the biogeochemical process of cave formation.

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Caves and Karst

This interactive resource adapted from the National Park Service presents the key concepts of cave and karst systems, including how and where they form, different types, and various cave environments.

Caves: Extreme Conditions for Life

This video segment adapted from NOVA raises the provocative idea that if life can exist in the most extreme environments on Earth — such as in dark, toxic caves — then perhaps living things can also survive in harsh environments on other planets.

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Dating Lava Flows on Mauna Loa Volcano, Hawaiʻi

In this video segment adapted from NOVA, scientists search for carbonized remains of plants preserved in lava flows to find out how long it has taken rain forests on Hawaiʻi to regenerate after a volcanic eruption.

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Deep-Sea Vents and Life's Origins

Deep-sea vents are home to life forms that do not rely on the Sun's energy. They depend instead on energy from volcanoes on the ocean floor. This video segment adapted from NOVA hypothesizes that life on Earth may have begun in this extreme environment.

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Everyday Radiation

How much radiation are we exposed to every day? Find out in this video segment adapted from FRONTLINE.

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Global Warming: The Physics of the Greenhouse Effect

This video segment adapted from NOVA/FRONTLINE examines the greenhouse effect, its role in keeping Earth habitable, and the industrial changes that have led to an increase in the planet's average temperature.

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A Hole in the Sky

This video segment adapted from Interactive NOVA profiles two scientists who were surprised in 1984 to discover a hole in our atmosphere's ozone layer as big as the United States.

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How Caves Form

This interactive activity from NOVA Online shows four different ways in which caves are formed: by rainwater, waves, lava, and bacteria.

Lava Sampling on Kilauea Volcano, Hawaiʻi

In this video segment adapted from NOVA, scientist Mike Garcia draws lava samples at the foot of the active Kilauea volcano to see if it is related to its neighboring volcano, Mauna Loa.

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Life Before Oxygen

This Interactive NOVA: "Earth" video segment looks at ancient organisms that lived anaerobically, the origins of photosynthesis, and the new forms of life this process made possible.

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Mars Dead or Alive: Mars Up Close

NASA scientist Steve Squyres narrates this visual tour from NOVA Online of the most revealing discoveries made by the Spirit and Opportunity rovers on Mars.

Mount Pinatubo: Predicting a Volcanic Eruption

This video segment adapted from NOVA relates the dramatic story of vulcanologists trying to predict the timing of the cataclysmic eruption of Mount Pinatubo in the Philippines.

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Radiometric Dating

In this video segment from A Science Odyssey: "Origins," scientists explain how Earth's age was determined by radiometric dating.

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Radon Radiation

The biggest source of environmental radiation might be in your home. Find out more in this video segment adapted from FRONTLINE.

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Sources of Radiation

This interactive activity from the NOVA Web site explores sources of radiation, both harmful and beneficial, natural and manmade.

Taking the Earth's Temperature

This video segment from FRONTLINE/NOVA: "What's Up with the Weather?" depicts research efforts to record Earth's past and present temperatures shifts.

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Virtual Cave

This interactive resource adapted from The Virtual Cave by Dave Bunnell, presents images of various features found in solution caves and includes detailed information on how these features are formed and where they occur.

Water Vapor Circulation on Earth

This simulation from the National Center for Atmospheric Research portrays annual patterns in water vapor and precipitation across the globe, illustrating general circulation patterns as well as seasonal and regional variation.