And water vapor gets into the atmosphere from plants, too, which is called transpiration.īecause air is cooler at higher altitude in the troposphere, water vapor cools as it rises high in the atmosphere and transforms into water droplets by a process called condensation. Snow and ice can also turn into water vapor, which is a process known as sublimation.
Water at the surface of the ocean, rivers, and lakes can become water vapor and move into the atmosphere with a little added energy from the Sun through a process called evaporation. Water in oceans and lakes is typically liquid but it is solid ice in glaciers, and often invisible water vapor in the atmosphere. Clouds are tiny droplets of liquid water or small ice crystals. Only a small fraction of the water on Earth (0.03%) is in lakes, wetlands, and rivers.Īs it moves through the water cycle, water often changes from a liquid, to a solid (ice), to a gas (water vapor). Most of the remaining 1% of Earth’s water is underground, in shallow aquifers, as soil moisture, or deep underground in rock layers. Most of the ice is in Antarctica, a smaller amount in Greenland in the Arctic, and a tiny fraction in mountain glaciers around the world. Sometimes the ice on Earth is included in the hydrosphere and sometimes it's seperated into a special part of the Earth system called the cryosphere. About 2% of the water on Earth is frozen in ice sheets near the poles and in glaciers. Of all the water in the hydrosphere, the vast majority, about 97% of it, fills the ocean. If you could put all that water together – like a gigantic water drop – it would be 1,500 kilometers (930 miles) across. It includes the water that’s in the atmosphere as clouds and vapor. It includes frozen water in snow, ice, and glaciers, and water that’s underground in soils and rocks. There are about 1.4 billion km 3 of water (336 million mi 3 of water) on Earth. That includes liquid water in the ocean, lakes, and rivers. It moves from place to place through the water cycle. Water is in the atmosphere, on the land, in the ocean, and underground. And the water you see in a river or stream may have been snow on a high mountaintop.
Rain falling today may have been water in a distant ocean days before. All of the water on Earth makes up the hydrosphere.
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