WEBVTT

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Earth holds a fixed amount of water.

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Ninety-seven percent of this water is salty ocean water.

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Only three percent of Earth's water is fresh water.

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Only one percent of this fresh water is accessible on the surface.

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Step one begins when the sun heats the ocean surface.

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Liquid water absorbs this heat and transforms into invisible gas.

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Eighty percent of all water vapor comes from our oceans.

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This warm gas rises high into the sky.

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Step two is transpiration, where plants release water vapor.

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First, roots pull liquid water up from the soil.

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Then, leaves release this water through tiny pores.

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One single oak tree releases forty thousand gallons of vapor every year.

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Step three is condensation, where rising vapor cools down.

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The temperature drops three point five degrees Fahrenheit for every thousand feet.

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This cold air forces the rising vapor to clump together.

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The vapor turns into liquid droplets to form clouds.

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Step four is precipitation, when clouds get too heavy with water.

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Gravity pulls this stored water back down to the ground.

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Above thirty-two degrees Fahrenheit, water falls as liquid rain.

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Below thirty-two degrees Fahrenheit, water freezes into snow.

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Step five is collection, which divides water into two main paths.

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Path one is runoff, where water slides into rivers.

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Path two is infiltration, where water sinks deep into the soil.

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Both paths eventually empty back into the ocean.

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Let us review the five steps of the water cycle.

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First, water evaporates from oceans and transpires from plants.

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Second, the rising vapor cools and condenses into clouds.

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Third, precipitation falls and collection returns it to the sea.

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This same water has recycled for four billion years.