Have you ever looked at a rocky section of mountain and noticed the striped layers of different colors? If you did, you studied geology. How did the layers get there and where did they come from? What materials make the different colors? Are the different colors all the same age or are some of them older? These are some of the questions geologists answer.
Geologists predict the future. By studying past earthquakes, landslides, volcanoes, and tsunamis, geologists can predict where this activity might happen in the future. When they discover why these events happen, we can avoid putting people in places where they might happen again.
Geologists work to find new sources of water, oil and natural gas. Geologists have learned that oil is usually located in the ocean near the margins of continents or in shallow seas on the continents. They have learned what types of rocks are usually located near these off-shore sites. By studying the earth formations around deposits of these natural resources, they can use this knowledge to find the best new places to drill.
By trying out these simple experiments, you can do a little geology on your own or with friends. These experiments can be done at home or school using materials available around the house.
HOW WATER HELPS FORM MINERALS
Fill a one gallon jar half full of water. Add handfuls of different materials to the water like sand, gravel, soil, powdered clay, a shell and a dead bug or two.
Tighten the lid on the jar and shake it about 20 times. Set the jar down and don’t disturb it. Look at it several times throughout the day. Watch how the different materials settle into layers. This is like the sediment that might form at the bottom of the ocean, a lake, or a river.
Don’t disturb the jar. Keep checking it until the water is clear. When it’s done, notice how the layers of different colors and sizes of material. What you see is sort of like the natural materials that settle on the ocean floor, a new layer each year. They lay there, one on top of the other, undisturbed for thousands of years.
How do you think nature decides which materials to settle on the bottom and which ones will be on top? What happened to the shell and the dead bugs? Are they on the bottom?
MAKE YOUR OWN QUICKSAND
Quicksand is a thick mixture of sand and water that appears to be a dry hard surface. It looks solid enough to walk on, but people have been known to be swallowed up in quicksand.
Work on a large sheet of newspaper (this can be messy). Combine 1 cup of cornstarch, and 1 cup of water in a bowl using a spoon until the mixture forms a thick paste. Lightly sprinkle 2 tablespoons of coffee grounds evenly over the top to give it a dry and even look.
Make a fist and lightly pound on the surface. Notice what happens and how it feels. Next, “walk” your fingers onto the quicksand, lightly pushing them down into the mixture.
What happened? When you use your fist, the mixture seems to be firm, but when you use your fingers, they sink to the bottom of the bowl. This is because the large molecules of quicksand swell and hook together, behaving more like a solid than a liquid. Also, the coffee grounds give the appearance of a smooth dry look, much like real quicksand.
This is an outdoor project that will demonstrate how water erodes soil.
Prepare a long U-shaped cardboard trough or a clear plastic tube. Fill the tube with course sand. Hold the tube at a slanting position with the end over a pan. Pour water a little at a time into the far end of the tube.
Watch how the water carries grains of sand as it flows out the end of the tube. Notice how the smaller grains of sand are carried out by the water but the larger grains are left behind. Notice the shape of the sand that flowed out the end of the tube. Did it form a half-circle pattern? This is called an “alluvial fan”.
Now repeat the experiment again, only this time add some small pebbles or stones into the sand. Pour the water in slowly and watch how the sand erodes away. What happens to the pebbles? Experiment by holding the tube at different angles to see the effect of a more steeply sloping hill on erosion.
Pour the water in faster and watch how the larger grains of sand and even the pebbles are carried out by the water.
Gather some more sand and make a small hill using your hands to pat it down hard. Use a spade or other tool to make a creek that meanders down the side of the hill. In places where the creek curves, add some softer sand. Add some pebbles as “boulders” along the edges of the creek.
Take a watering can and water the top of the hill. Watch how the water from the “rain” flows down the creek. What happens at the curves and boulders? Create a harder rain by pouring water out of the can faster. Notice the effects of erosion on your mountain.
An excellent Internet resource about geology with pictures and stories from around the world is geology.com. Kids and adults will enjoy learning about everything from the mysterious Sliding Rocks of Racetrack Playa to the making of the Grand Canyon.