The Hydrologic Cycle
As the name implies, The Hydrologic cycle has to do with water, and what happens with water on the planet. All life depends on water. Without it, nothing can live. This is why Astronomers and other scientists search for signs of water when investigating other planets and moons. If there is water, there may be life.
The heat of the Sun causes water to evaporate, turning liquid water into a gas (water vapor). Because water vapor is warm (because of the Sun), it rises into the atmosphere (Warm air is lighter than cold air). This causes humidity. Temperature and atmospheric pressure determine how much water vapor the air can hold. The higher the temperature and pressure, the more water vapor. Did you know that about 80% of evaporation comes from the worlds oceans? This is because about 71% percent of the planet is covered by water! The other 20% of evaporation comes from lakes and rivers and from the ground and vegetation (plants and trees).
As water vapor rises in the atmosphere, it begins to cool. When the atmosphere cools to the point where it can no longer hold the water vapor it condenses back into liquid water in the form of microscopic droplets. But condensation cannot happen without something for the water vapor to condense on. Water vapor will condense onto dirt, dust, and even bacteria floating in the air. As more water vapor condenses, the droplets get bigger and soon begin to cling together. This is how clouds are formed. The water vapor in the air along with clouds, is then spread over land by the wind (Transportation).
The next step in the Hydrologic cycle is precipitation. Precipitation can come in the form of rain, snow, sleet, or hail. When clouds begin to have more water than they can hold, the water falls back to Earth as precipitation and the cycle begins again.
It is amazing to think about how all these processes happen in order to sustain life on this planet and how any disruption can cause problems. This is why we need to take care of the Earth and all it contains, so life will continue!