Earth is the third planet from the sun, after Mercury and Venus, and before Mars. It is about 150 million kilometers (about 93 million miles) from the sun. This distance, called an astronomical unit (AU), is a standard unit of measurement in astronomy. Earth is one AU from the sun. The planet Jupiter is about 5.2 AU from the sun—about 778 million kilometers (483.5 million miles).

The hydrosphere is composed of all the water on Earth. Nearly three-fourths of Earth is covered in water, most of it in the ocean. Less than three percent of the hydrosphere is made up of freshwater. Most freshwater is frozen in ice sheets and glaciers in Antarctica, the North American island of Greenland, and the Arctic. Freshwater can also be found underground, in chambers called aquifers, as well as rivers, lakes, and springs. planet earth illustration surrounded by hands, Earth Overshoot Day Earth Day, Earth, globe, hand, recycling png 800x800px 806.28KBplanet Earth illustration, Atmosphere of Earth Atmosphere of Earth Space, Galaxy Universe, blue, atmosphere, computer png 2576x3307px 4.67MB Earth and the rest of the solar system formed about 4.6 billion years ago from a huge, spinning cloud of gas and dust. Jupiter, Saturn, Uranus, and Neptune all have atmospheres made mostly of hydrogen and helium. These planets are called gas giants, because they are mostly made of gas and do not have a solid outer crust.

Plate tectonics are also responsible for landforms such as geysers, earthquakes, and volcanoes. Tectonic activity around the Pacific plate, for instance, creates the Ring of Fire. This tectonically active area includes volcanoes such as Mount Fuji, Japan, and earthquake-prone fault zones such as the west coast of the United States. Eventually, Earth began to cool and its materials began to separate. Lighter materials floated upward and formed a thin crust. Heavier materials sank toward Earth’s center. Eventually, three main layers formed: the core, the mantle, and the crust. city and ocean themed earth animated, Earth, Earth, Green Earth, environmental protection, material Taobao, globe, environmental, green Vector png 3288x2849px 5.82MB Earth has one natural satellite, the moon. Earth is the only planet in the solar system to have one moon. Venus and Mercury do not have any moons, for example, while Jupiter and Saturn each have more than a dozen.The atmosphere has a layered structure. From the ground toward the sky, the layers are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. Up to 75 percent of the total mass of the atmosphere is in the troposphere, where most weather occurs. The boundaries between the layers are not clearly defined, and change depending on latitude and season. earth planet, Earth Environmentally friendly Natural environment, Earth,protect the Earth, globe, environmental, recycling png 5512x5499px 29.96MB All living or once-living materials contain carbon. These materials are organic. Plants and other autotrophs depend on carbon dioxide to create nutrients in a process called photosynthesis. These nutrients contain carbon. Animals and other organisms that consume autotrophs obtain carbon. Fossil fuels, the remains of ancient plants and animals, contain very high amounts of carbon. Each journey around the sun, a trip of about 940 million kilometers (584 million miles), is called a revolution. A year on Earth is the time it takes to complete one revolution, about 365.25 days. Earth orbits the sun at a speedy rate of about 30 kilometers per second (18.5 miles per second). Magnificent. The commentary is great, really thoroughly researched; the pictures are stunning."—Tom Shippey, author of The Road to Middle-earth and J.R.R. Tolkien: Author of the Century

Accompanied with numerous genealogical tables and a unique Chronology of the First Age, it will provide an indispensable aid to every reader’s discovery of Tolkien’s world. Coupled with numerous genealogical tables and a unique Chronology of the First Age, it will provide an indispensable aid to every reader’s discovery of Tolkien’s world.Earth’s physical environment is often described in terms of spheres: the magnetosphere, the atmosphere, the hydrosphere, and the lithosphere. Parts of these spheres make up the biosphere, the area of Earth where life exists. As organisms die and decompose, they release carbon into the ocean, soil, or atmosphere. Plants and other autotrophs use this carbon for photosynthesis, starting the carbon cycle again. Daytime Atmosphere of Earth Computer, The vast sky, starry night, watercolor Painting, texture, studio png 1616x1215px 4.07MB