9.1: The Water Cycle
The Water Cycle
How many times a day do you take water for granted? Do you assume the tap will be flowing when you turn on your faucet? That the shower will turn on, the toilet will flush, and you’ll have water to cook your meals? Not only is water necessary for many of life’s functions, it is also a considerable geologic agent. Water can sculpt the landscape dramatically over time, by both carving canyons and depositing thick layers of sediment. Some of these processes are slow and result in landscapes worn down over time; others, such as floods, can be dramatically fast and dangerous.
Figure 9.1: Earth's water is always in movement, and the natural water cycle (hydrologic cycle), describes the continuous movement of water on, above, and below the surface of the Earth. Water is always changing states between liquid, vapor, and ice, with these processes happening in the blink of an eye and over millions of years. (Public Domain, Howard Perlman and John Evans/USGS Links to an external site.)
What happens to water during a rainstorm? Imagine that you are outside in a parking lot with grassy areas nearby. Where does the water from the parking lot go? Much of it will flow across the surface and eventually join a stream. What happens to the rain in the grassy area? Much of it will infiltrate, or soak into the ground. Water is continually recycled through the atmosphere, to the land, and back to the oceans. This movement of water through the Earth System is referred to as the hydrologic (water) cycle Links to an external site. (Figure 9.1). At Earth’s surface, this cycle, powered by the sun, operates easily since water can change form from liquid to gas (or water vapor) quickly. The majority of water is found in oceans, but freshwater can be found in lakes, rivers and trapped away in glaciers and ice sheets. Additional water resources are also found in the ground, and will be discussed in another chapter (Figure 9.2).
Figure 9.2: Most of the Earth’s water is found in oceans and is therefore saltwater. Earth’s freshwater sources are mostly locked within glaciers and ice caps and as groundwater. Rivers and lakes make up only a small fraction of Earth’s freshwater resources. (Public Domain, USGS Water Science School Links to an external site.)
Those who study water, water resources, or the landforms made by water, may have many titles, including hydrologist, hydro-geologist, geomorphologist, or geochemist to name a few. Like many other geoscientists, working with other disciplines is common, with a heavy influence from both math and technology. Many are employed by universities where they teach and/or do research, and state and federal agencies, including geological surveys, like the California Geological Survey Links to an external site. or United State Geological Survey (USGS) Links to an external site.. Additional career pathways are available in the private sector including in mining and natural resource extraction or in hazard mitigation and assessment. Many of these career options require a college degree and postgraduate work. If you are interested, talk to your geology instructor for advice. We recommend completing as many math and science courses as possible. Also, visit National Parks Links to an external site., CA State Parks Links to an external site., museums, gem & mineral shows, or join a local rock and mineral club. Typically, natural history museums will have wonderful displays of rocks, including those from your local region. Here in California, there are a number of large collections, including the San Diego Natural History Museum Links to an external site., Natural History Museum of Los Angeles County Links to an external site., Santa Barbara Museum of Natural History Links to an external site., and Kimball Natural History Museum Links to an external site.. Many colleges and universities also have their own collections/museums.