“An Experiment in Weather”
(1) Two plastic jar/lid (jug size)
(2) Brick fragments
(3) Field trip to beach
How rain, wind, temperature (sun) wear on rocks.
1) Fill the big plastic jug half full of water. Place the brick fragments (pieces) in the jug.
2) Four or five times a day one student can shake the jug 50 times. (This will stimulate the action of water erosion.)
3) At the end of the week, drain the water into another container. See how the amount of sediment that has formed in the bottom of the jug. Also examine the chunks of brick to see if the effects of erosion have taken place.
4) As an accompanying experiment, have each student bring in a rock from his/her own yard or neighborhood. Wash the rocks off and place them in the plastic jug and conduct the same experiment as described for the bricks.
5) At the end of the week, see how much sediment has formed. Did the rocks form less than the bricks? If so, why?
Students should begin to see that changes in rocks occur very slowly.
Wind, too, can be a great weathering force. It can pick up fine particles of rock and carry them great distances. It can also hurl these same particles against other rock surfaces thus wearing them away abrasively (by constant rubbing).
Anyone who has walked on any beach has seen the power of wind and waves on beachside rocks. Mounds of smooth, rounded rocks and pebbles abound in certain areas. Once they were sharp, jagged chunks of rock. They (sand mounds) tell of thousands of years of tossing against each other, gradually wearing away to the almost polished looking stones.
EXPERIMENT IN HOW SEDIMENTATION OCCURS
(1) Plastic jar/lid
OBJECTIVE This activity will explore how layers of solid form from a mixture of solids and water.
Moving water carries solids (heavy rocks) as it flows. Heavier and larger solids (heavy rocks) drop to the bottom first. A rocky stream is a rocky stream because the heavier rocks are deposited by the moving water first while the lighter solids are carried along to deltas and swamps where the water is not moving fast.
Solid matter that settles to the bottoms of rivers, streams, lakes, and oceans is called SEDIMENT. Sediment can build up on the bottoms of bodies of water, and under great pressure from the weight of many layers, turns into rock. This type of rock is called SEDIMENTARY rock. A familiar example of sedimentary rock formations once under water is seen in the layers of rock in the Grand Canyon. (It would be good to show a picture of Grand Canyon walls here.)
Slowly add water to the jar until it is almost full, put the lid on tightly and shake the jar until contents are well-mixed.
Have the class observe the layers that form in the first minute. Set the jar aside and observe the results periodically. After 30 minutes, well-defined layers of solids should be seen. The finest solids will take several hours (or even overnight) to settle. Leave the jar untouched to see how long it takes for the water to clear completely.
1) Which layer formed first? What caused that layer to settle first? (The pebbles settled first because they were the heaviest.)
2) Which layer formed last? Why? (The soil settled last because it was the lightest.)
3) If the water had been moving, which solid would have been carried the furthest the fastest? (The soil because it is the lightest and easiest to move.)
(found on New England beaches)
Field trip looking for granite rocks
One of the most common rocks in the world, and certainly in New England, is granite. It is the salt and pepper looking rock most of us can find right in our yards. It can also be pinkish colored and dotted with gray and black. Granite is an example of a “fire rock,” one that is formed from hot, molten rock within the earth’s surface.
The hot, liquid rock comes up to or near the surface of the earth and cools slowly.
Rocks are mixtures of many different minerals. Granite is a mixture of quartz, feldspar, mica, and hornblende.
Quartz is a very hard mineral which is found in granite, and gives granite its durability. Granite is used in buildings and cemetery monuments because it lasts a long time.
Feldspar, the principal ingredient of granite, can be gray, white, or pink and gives granite its color. Tiny sheets of mica give granite its sparkle, and hornblende (or black biotite mica) gives it its black spots.
You can tell how quickly granite cooled under the surface of the earth by how large the crystals of these different minerals are. The quicker it cooled, the smaller the crystals. Granite with big, fat spots of quartz and hornblende cooled very slowly. It might be interesting to compare different granite rocks students bring in to compare the size of the crystals.
ACTIVITY Look through a magnifying glass and seek the various granules in New England sand.
(1) field trip to the beach
(2) magnifying glass
Most of the sandy beaches in New England (our part of the U.S.A.) are a mixture of grains of quartz, biotite, feldspar, mica, and hornblende. That is because these are the ingredients of our most common rock, granite. Quartz makes the clear crystals in the sand, biotite or hornblende are the black grains, feldspar makes the pinkish-beige grains, and mica is the tiny, flat flakes that glisten when the sun shines through the water.
A geologist can look at sand and tell from what kind of earth formations the sand originated. A coral reef (in the state of Florida) will make a different kind of sand than a granite coast. Volcanic rock area will produce a different looking sand than sand created by eroded seashells on a shell beach. Why? (Answer: a shell is not a rock.)
Look closely at the sand samples in this lesson using a hand lens or microscope (if available, or magnifying glass). On your observations sheet, list the colors you can see in the sand. Are they the same colors you can see in the weathered granite rocks? Where do you think the sand began?
AN EXPERIMENT IN MAKING SAND
(1) Enough zip lock bags for your class
(2) Variety of rocks
(3) Magnifying glass
OBJECTIVE Students will learn how erosion (a force moving rock, gradually wear it, in tiny particles, away).
1) Have students bring in 12 rocks that they have collected outside of school. (Try to find a variety of rocks.) Have them shake the bags vigorously (but not too vigorously to break bags). Support the bottom of the bag with one hand.
2) Have students dump the contents of the bags after a few minutes out on the desks keeping the contents in one small area.
3) Using hand lenses, examine the contents carefully to see if any sand was made. If so, see from which rocks the sand was made.
4) If the bags are still in good shape, do the activity again to see if a different kind and amount of sand is made using the remaining six rocks of the students collected.