It's easy to find rocks - they're just about everywhere in nature! If you live near mountains or rocky shores, you can easily find small pieces of rocks that have broken away from large boulders or cliffs. If you live near an ocean, lake, or stream, you can find pebbles and other stones. You can even find interesting rocks on a gravel road, driveway, or at a park! (Important Note: it is illegal to take anything - including rocks - from national parks, monuments, and most state parks. Be sure to ask for permission before taking rocks from someone else's property.)
Collect some of the rocks you see that you like best. Look for ones with interesting shapes and colors. Store them in a box or bag until you get home, then rinse them off and dry them. Notice how much different they look when they're wet instead of dry. The water cleans dirt off of them, but also helps them reflect light so the colors and features inside are easier to see.
Do you notice any interesting patterns, lines, or colors in your rocks? Get a closer look at crystals, cracks, and other features of your rocks with a magnifying glass. Sort your rocks by their color, size, or texture. An empty egg carton makes a great place to store your collection - you can put one rock in each cup or put several similar ones together.
To learn more about the rocks you find, visit this website and see if you can identify any of them. (Click on "Play," then "Geology," and then "In the Field: Rock Sherlock.")
Buy this convenient Rock Study Kit to learn about rocks!
Learn more about each type of rock with the activities below.
Igneous rocks are formed when melted rock, called magma or lava, cools. As it cools, it becomes hard. You can see how melted rock can cool into igneous rock with this simple (and tasty!) activity. You will need a bowl of ice cream and some hot fudge sauce that will harden (not chocolate syrup).
Pour some chocolate sauce over the ice cream. Watch what happens. Does the chocolate start to look different after a minute or two? When it comes into contact with the very cold ice cream, it cools down quickly.
In this example, the ice cream represents the earth and the hot fudge sauce represents lava (melted rock from inside the earth). As the lava spills onto the earth from inside a volcano, it starts to cool down and quickly hardens back into rock.
Sedimentary rocks are formed when dirt, sand, and small bits of rocks (also known as sediment) settle down and stick together, often at the bottom of a lake. To see how this works, fill a clear jar with water and add a few handfuls of different sediment such as sand, dirt, soil, leaves, or pebbles. Screw the lid on the jar and shake it up well, then set the jar on a table and watch as the sediment starts to settle to the bottom of the jar. The largest pieces fall to the bottom fastest, but eventually most of the sediment will settle. In nature, sediment settles in layers. Over a long period of time, more sediment forms new layers on top of the last one. Eventually, the layers stick together and become rock.
You can use some aluminum foil to represent a sedimentary rock. Tear a piece about 12" long and crumple it up. The shape you end up with will be your "rock." If you look closely the crumpled foil, you'll notice tiny folds going in all different directions. Sedimentary rocks are made of lots of particles that can stick together in all different directions. There are also spaces in your "rock" because sedimentary rocks often have holes called pores in them.
A metamorphic rock is formed when an old rock, which could be either igneous or sedimentary, is exposed to a lot of heat and a lot of pressure. The heat changes the minerals that the rock is made of and crystals are allowed to grow in the spaces left in sedimentary rocks. The very strong pressure that presses down on the rock flattens it together. The changes from the heat and pressure together make a brand new rock!
You can show how this works by flattening your foil sedimentary "rock" with a rolling pin or hammer. First, flatten it a little by pressing it hard against a wall or table. Then use a rolling pin or hammer to see if you can get it any flatter and take a look at it. Does it look a lot different from before you flattened it? Most of the little folds of foil should be going the same direction now. All that pressing made the folds line up on top of each other. The hammer or rolling pin represents the pressure that the rock would be exposed to over time when it turns to a metamorphic rock. Of course, this does not include the heat that helps change rocks to metamorphic ones, but you can see how pressure is important to change them.
To learn more about roots and minerals, visit this Teaching Tip.