The hydrosphere is all of earth's water. This water is constantly circulating throughout the biosphere in a process called the hydrologic cycle. (See our page about the water cycle, which is another name for the process).Energy can be obtained from water as it makes its way downwards, back to the oceans (5) under the influence of gravity ... we use hydroelectric dams to extract some of this energy. The whole cycle is powered by the sun, which supplies the energy to evaporate (1) trillions of tons of water every day, from all bodies of water. Because the earth rotates, and is tilted on its axis, and because some areas of the surface warm more than others, different regions of the atmosphere will heat at different rates. Some areas will be warmer than others. This creates convection currents, which cause the air to move around. The moving air takes the water vapour with it. As this air moves around, it may move upwards, or it may encounter an area of low pressure, or it may do both. When it does, it expands and cools. The water vapour will condense, forming liquid water droplets. Lots of these droplets make clouds. If water droplets are lifted to great heights by a storm, where it is very cold, or if the falling droplets encounter a cold layer of air, the water may solidify to become snow. Snowflakes occur when water turns to a solid under conditions which allow the molecules to build on one another in a crystalline pattern. Why are they always 6-sided? Find out here. The hydrologic cycle is supposed to be a closed loop. That means that the amount of water circulating through the biosphere is a fixed amount ... it doesn't change. Humans have inserted themselves into this loop, drawing off some of the water for our own purposes, and then returning it to the cycle. We see it as a renewable resource, one that keeps replenishing itself after we use it.  Unfortunately, our demand for water is increasing all the time, and we sometimes don't put back the water we've used in the same condition it was when we took it. It's dirty, polluted, hot, and sometimes even radioactive. The result is that, even though the water cycle is constantly renewing our water supply, the available supply of clean water is getting smaller and smaller. We've heard it said that there is not a single square mile on any of the oceans where you can't see garbage floating. Most rivers in the world are polluted by human fecal matter and bacteria that get there from sewage pumped into the water.  Some North American waterways and lakes are reported as having 'safe levels' of these materials ... which just means that the levels that exist are too small to make you sick ... we hope.Only by ensuring that the people you elect to government care at least as much about the environment as they do about the companies who pollute it in the name of profit, will the problem get solved. |