How much water is on Earth and how does it circulate between the ocean, the atmosphere, and the land?
About 1.37 billion cubic kilometers (329 million cubic meters) of water exists at Earth's surface, the vast majority (approximately 97%) in the ocean. About 1.8% is bound in glaciers and the great ice caps of Greenland and Antarctica. Only about 0.64% is fresh, temporarily residing in rivers, lakes, wetlands, and below the surface as groundwater. Water is in constant motion, circulating between the ocean, the atmosphere, and the land.
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This water cycles continuously. The hydrologic cycle, as the process is called, is powered by solar radiation (with a small assist from geothermal energy). Water vapor rising from the sea surface condenses into clouds and forms rain and snow. About 80% of this precipitation falls back into the ocean, and the 20% that falls on land eventually finds its way there after spending various amounts of time moving through plants, masses of ice, sediments, and streams.
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B) it contains abundant organic matter.
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