Groundwater Movement Water that accumulates beneath the surface of the Earth is called groundwater. Contrary to popular belief, groundwater does not form underground "rivers," but is actually found in the small spaces and cracks between rocks and other material such as sand and gravel. Groundwater supplies about 38 percent of the water used for agriculture in the United States. Water enters aquifers by soaking down into the ground through a process called "percolation." For water to move in an aquifer, the pores between rock materials and fractures in rock must be connected. The capacity of rock material to transmit water is called "permeability." Water moves through different materials at different rates-faster through gravel, slower through sand, and much slower through clay. Therefore, gravel is more permeable than sand, which is more permeable than clay. If hazardous waste, chemicals, heavy metals, or oil collect on the surface of the ground, rain or runoff percolating into the soil can carry these substances into the groundwater.
The following activity involves learning how water moves through rock
material such as sand, gravel, and clay. Procedure: Ask students to predict how water will move through gravel, sand, and clay. Then have students test their hypothesis by placing gravel, sand, and clay in the three soda bottles or plastic cups. The material should fill the containers to a depth of about 8 cm. Have students look closely at each container (a hand-held magnifying glass works well). To demonstrate how groundwater moves through underground rock formations, pour about 120-240 mL of water (or colored water) into each container and discuss the results. Which container emptied the fastest? (the container with the gravel) Which emptied the slowest? (the one with clay) Ask the students how the different materials would influence water movement in natural systems. Energy Resources Have students compile a list of activities they do that require energy. Then ask the class to break up into groups of three or more students, assign several of the activities from the list to each group, and have each group prepare a report answering the following questions:
Once the report is complete, groups should report back to the entire class. Students should take notes on each group's report. Wind Energy Wind is moving air caused by differences in air pressure. Air moves from areas of greater density (pressure) to areas of lesser density. An area of greater air pressure surrounded by lesser air pressure is called a high. An area of air pressure that is lower than the surrounding area is called a low. Winds blow into a low because the air is less dense there. In locating sites for a possible wind farm (a collection of windmills used to produce electricity), many factors must be considered: the constancy of the wind, its velocity (speed), the distance to carrier lines, and accessibility. As with any energy source, wind energy has advantages and disadvantages. It does not cause air pollution and it will never be used up. On the other hand, hundreds or even thousands of wind turbines are necessary to produce significant amounts of energy. This takes up a lot of space, and some people do not like the appearance of so many turbines on the landscape. In the following activity, students imagine that they are planning a wind farm. To select a site for the wind farm, students construct anemometers to measure wind speed and compare measurements of average wind speeds. Materials: You will need three plastic cups (about 8 oz), three knitting needles, a large cork, a wooden pole or 1/2"-3/4" dowel, a hammer, a nail 3 cm longer than the cork, two metal washers, and a bright-colored marker. Procedure:
Shelly Fischman Extend the activity with the following discussion ideas:
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