Water on Earth
Standard 5 E.S 10
Where is all of the Earth's water?
The ocean holds 97 percent of the Earth's water; the remaining three percent is freshwater found in glaciers and ice, below the ground, or in rivers and lakes.
Of the world's total water supply of about 326 million cubic miles of water, over 96 percent is saline, found in the ocean.
Of the three percent of the water that is not in the ocean, about 69 percent is locked up in glaciers and icecaps. Ninety percent of that frozen water is in Antarctica and about nine percent covers Greenland.
Of the remaining freshwater, 30 percent of it is groundwater, captured below our feet. About 0.3 percent is found in rivers and lakes. This means that the water source we are most familiar with in our everyday lives, rivers and lakes, accounts for less than one percent of all freshwater that exists on Earth.
A very small percentage of water (0.1 percent of all water) is also found in the atmosphere.
A cloud is a large collection of very tiny droplets of water or ice crystals. The droplets are so small and light that they can float in the air.
Click here to watch a video and learn more about clouds
How are clouds formed?
All air contains water, but near the ground it is usually in the form of an invisible gas called water vapor. When warm air rises, it expands and cools. Cool air can't hold as much water vapor as warm air, so some of the vapor condenses onto tiny pieces of dust that are floating in the air and forms a tiny droplet around each dust particle. When billions of these droplets come together they become a visible cloud.
Why are clouds white?
Since light travels as waves of different lengths, each color has its very own unique wavelength. Clouds are white because their water droplets or ice crystals are large enough to scatter the light of the seven wavelengths (red, orange, yellow, green, blue, indigo, and violet), which combine to produce white light.
Why do clouds turn gray?
Clouds are made up of tiny water droplets or ice crystals, usually a mixture of both. The water and ice scatter all light, making clouds appear white. If the clouds get thick enough or high enough all the light above does not make it through, hence the gray or dark look. Also, if there are lots of other clouds around, their shadow can add to the gray or multicolored gray appearance.
Why do clouds float?
A cloud is made up of liquid water droplets. A cloud forms when air is heated by the sun. As it rises, it slowly cools it reaches the saturation point and water condenses, forming a cloud. As long as the cloud and the air that its made of is warmer than the outside air around it, it floats!
How do clouds move?
Clouds move with the wind. High cirrus clouds are pushed along by the jet stream, sometimes traveling at more than 100 miles-per-hour. When clouds are part of a thunderstorm they usually travel at 30 to 40 mph.
Why do clouds form at different heights in the atmosphere?
The characteristics of clouds are dictated by the elements available, including the amount of water vapor, the temperatures at that height, the wind, and the interplay of other air masses.
How is fog formed?
There are many different types of fog, but fog is mostly formed when southerly winds bring warm, moist air into a region, possibly ending a cold outbreak. As the warm, moist air flows over much colder soil or snow, dense fog often forms. Warm, moist air is cooled from below as it flows over a colder surface. If the air is near saturation, moisture will condense out of the cooled air and form fog. With light winds, the fog near the ground can become thick and reduce visibilities to zero.
(Graphic Credit: USA TODAY.)
You need warm air! Southerly winds bring warm, moist air over cold ground or snow.Fog Forms! Moisture condenses into fog as air is cooled from below.
Click here to view pictures of different types of clouds