Hobbies And Interests
Water
Most land erosion is caused by water. To demonstrate this, place a pile of mud outside the school and bring the students outside to observe the experiment. Once assembled, turn a water hose on the pile, effectively demonstrating how rivers, waves and rain erode the land. Have the students try experiments of their own. They could build a dirt pile in their gardens at home and observe the effect of rainfall, or perform an experiment on the ability of grass to keep soil in place. They could also fill a tilted baking tray with soil and make a path for water to trickle down, then observe how the path changes until the water finds the most direct route.
Wind
Although wind is a considerably weaker erosive force than water, it is still an effective one. Usually strong winds, including tornadoes and hurricanes, will blow particles of sand and rock around, which in turn grind against larger rocks to wear them down. To replicate this in the classroom, have the children pour sand into a baking tray then blow on it as hard as they can. Alternatively, place an electric fan in a sand pit. Over time a ravine will appear in the sand, which is how sand dunes are formed.
Ice
Glaciers are the slowest-moving eroding force, but can easily be replicated in the classroom. Ask students to pour sand into a baking tray to make a hill; they may need to dampen the sand slightly. Now pour sugar on top of the hill. Observe how the sugar expands down the side of the sand as you keep pouring. When a glacier forms it is because snow has fallen on top of a mountain. As the snow continues to fall it squeezes the air out of the snow underneath, making the ice incredibly hard; this gradually moves down the mountainside, tearing up rocks and trees as it moves. Another experiment to show the strength of ice could be to fill a container with water and place a lid on top. If the children then place the container in a freezer the water will expand and lift the lid.
Chemicals
The past two hundred years has seen a huge increase in pollutants entering the atmosphere, which has contributed to an effect known as acid rain. In this case, rain water carries with it various other chemicals which can erode rocks. To observe this in the classroom, use a piece of limestone and either submerge it in hydrochloric acid, or drop hydrochloric acid onto it at regular intervals. Observe how the limestone erodes as it reacts to the acid. Ask the children to think of why this might be a problem; an example would be limestone buildings.