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Experts in science & technology provide insightful commentary and informed perspective.

Shipwrecks are as old as seafaring humans.

There are 59 national parks in the United States.

Glaciers are giant rivers of ice.

Coral reefs support entire ecosystems of animals.

Endangered species are those in danger of extinction.

Lightning is basically a giant spark of static electricity.

Caves can range in size from single rooms to miles-long passageways.

Most of Earth's volcanoes are located along the Pacific Ring of Fire.

Earth's atmosphere is about 78 percent nitrogen, 21 percent oxygen, with trace amounts of water, argon, carbon dioxide and other gases.

The Arctic is largely an ice-covered ocean.

Deserts can be hot and dry, like the Sahara, or cold and dry, like Antarctica.

Tsunamis can be created by earthquakes, underwater landslides and volcanic eruptions.

El Niño and La Niña are parts of a climate cycle that has implications for weather around the planet.

Two million species are known on Earth, millions more remain undiscovered.

Conservation efforts aim to save both individual species and entire ecosystems.

Coral reefs and rainforests are some of the most biodiverse places on Earth.

Invasive species, introduced by accident or on purpose, can wreak havoc on native ecosystems.

Earth's four seasons are caused by the yearly revolution of the planet around the sun and its tilt.

Earth's interior consists of it's mantle, outer core and inner core layers.