We also enjoy protection from Earth's magnetic field, generated by our planet's rotation and its iron-nickel core. Ninety percent of Earth's atmosphere lies within just 10 miles of the planet's surface. But for all that our atmosphere does, it's surprisingly thin. The atmosphere not only nourishes life on Earth, but it also protects it: It's thick enough that many meteorites burn up before impact from friction, and its gases-such as ozone-block DNA-damaging ultraviolet light from reaching the surface. This extra heat has altered Earth's weather patterns in many ways. In the last two centuries, humans have added enough greenhouse gases to the atmosphere to raise Earth's average temperature by 1.8 degrees Fahrenheit. On average, Earth's surface temperature is about 57 degrees Fahrenheit without our atmosphere, it'd be zero degrees. Much like a greenhouse, this blanket of gases absorbs and retains heat. Protective fields and gasesĮarth's atmosphere is 78 percent nitrogen, 21 percent oxygen, and one percent other gases such as carbon dioxide, water vapor, and argon. When plates of continental crust collide, mountain ranges such as the Himalaya are pushed toward the skies. Many volcanoes form as seafloor crust smashes into and slides beneath continental crust.

Earthquakes rumble as these plates snag and slip past each other. As these plates collide, tear apart, or slide past each other, they give rise to our very active geology. These bodies of water contain 97 percent of Earth's volcanoes and the mid-ocean ridge, a massive mountain range more than 40,000 miles long.Įarth's crust and upper mantle are divided into massive plates that grind against each other in slow motion. But unlike its rocky siblings, almost 70 percent of Earth's surface is covered in oceans of liquid water that average 2.5 miles deep. Like Venus and Mars, Earth has mountains, valleys, and volcanoes. On land, the continental crust is an average of 19 miles thick, but the oceanic crust that forms the seafloor is thinner-about three miles thick-and denser. Beyond the outer core lies the mantle, a 1,800-mile-thick layer of viscous molten rock on which Earth's outermost layer, the crust, rests.

The inner core is surrounded by the outer core, a 1,400-mile-thick band of iron and nickel fluids. Over time, Earth's interior-which is made mostly of silicate rocks and metals-differentiated into four layers.Īt the planet's heart lies the inner core, a solid sphere of iron and nickel that's 759 miles wide and as hot as 9,800 degrees Fahrenheit. Many layers, many featuresĪbout 4.5 billion years ago, gravity coaxed Earth to form from the gaseous, dusty disk that surrounded our young sun. On two specific dates each year-called the equinoxes-both hemispheres get illuminated equally. In the spring and fall, each hemisphere receives similar amounts of light. Whichever hemisphere is tilted closer to the sun experiences summer, while the hemisphere tilted away gets winter. This axis of rotation is tilted 23.4 degrees away from the plane of Earth's orbit around the sun, giving us seasons. Astronomers define this distance as one astronomical unit (AU), a measure that serves as a handy cosmic yardstick.Įarth rotates on its axis every 23.9 hours, defining day and night for surface dwellers. During this circuit, our planet is an average of 93 million miles away from the sun, a distance that takes light about eight minutes to traverse. Though we can't feel it, Earth zooms through its orbit at an average velocity of 18.5 miles a second. Since our calendar years have only 365 days, we add an extra leap day every four years to account for the difference. Our dance around the sunĮarth orbits the sun once every 365.25 days. Find out the origins of our home planet and some of the key ingredients that help make this blue speck in space a unique global ecosystem. Earth is the only planet known to maintain life.

Earth in motion fitness