Did you know that some people have a job where they study rocks? These people are called geologists, and they study the Earth, which includes all the rocks. This science is called geology. Geologists explore how our Earth is made and how it changes over time. They look at valleys, mountains, rivers, and lakes to understand how they were formed.
Geologists study many things like rocks, landslides, earthquakes, and volcanoes. They also learn about how humans and the Earth can help each other so we don’t run out of natural resources. It’s important to study the Earth to know how it changes and how we can keep it healthy for a long time. This is called being sustainable.
Today, let’s focus on one part of a geologist’s job: studying rocks. You might have seen many rocks, but did you know they are not all the same? Rocks are different based on how they were formed. There are three main types of rocks: sedimentary, metamorphic, and igneous.
Sedimentary rocks are made from tiny pieces of sand, shells, pebbles, and other materials. These pieces are called sediment. Sediment forms when rocks break down into small bits. Over time, layers of sediment pile up and press together to form a rock. Sedimentary rocks are usually soft and can crumble easily. They are also the only rocks that might have fossils, which are imprints of plants or animals from long ago. Examples of sedimentary rocks include limestone, shale, sandstone, and chalk.
Metamorphic rocks are formed deep under the Earth’s surface. It takes millions of years, along with a lot of heat and pressure, to create these rocks. They often have ribbon-like layers and shiny crystals. These crystals form as minerals grow slowly over time. You might have a metamorphic rock in your kitchen! Marble, slate, and quartz are common metamorphic rocks often used for countertops. If you have one, look closely to see the layers and crystals.
Igneous rocks form when magma cools and hardens. Magma is hot, melted rock found deep inside the Earth, like in a volcano. When magma erupts from a volcano, it is called lava. As lava cools quickly, it can form rocks that look shiny or glass-like. Sometimes, gas bubbles get trapped inside, leaving tiny holes in the rock.
There are two types of igneous rocks: intrusive and extrusive. Intrusive igneous rocks form when magma cools slowly inside the Earth, allowing large crystals to form. Granite is an example of this type. Extrusive igneous rocks form when lava cools quickly on the Earth’s surface, leaving little time for crystals to form. Basalt, andesite, and pumice are examples. Sometimes, lava cools so fast that no crystals form, creating obsidian, a beautiful rock!
Let’s get rockin’!
Well done, everybody! We’ve learned that not all rocks are the same. They have different features and processes that make them unique. Remember, sedimentary rocks are soft and crumble easily, metamorphic rocks have layers and shiny crystals, and igneous rocks are volcanic and can be shiny or have tiny holes. Keep being a geologist! The next time you pick up a rock, see if you can tell if it’s sedimentary, metamorphic, or igneous. Doesn’t geology rock?
Rock Collection Adventure: Go on a rock hunt in your backyard or a nearby park. Collect a few different rocks and bring them home. With the help of an adult, try to identify if they are sedimentary, metamorphic, or igneous rocks. Use a magnifying glass to look for layers, crystals, or tiny holes. Draw a picture of each rock and write down what type you think it is and why.
Rock Cycle Story: Imagine you are a rock going through the rock cycle. Write a short story or draw a comic strip about your journey. Start as a piece of sediment, then become a sedimentary rock, transform into a metamorphic rock, and finally melt into magma to become an igneous rock. Share your story with your classmates or family.
Kitchen Geologist: With an adult’s help, explore your kitchen for items made from rocks. Look for countertops or tiles made of marble, granite, or slate. Use a magnifying glass to observe any patterns or crystals. Discuss with your family how these rocks might have formed and why they are useful in the kitchen.
**Geology and Rocks for Kids**
Did you know there are people who study rocks for their job? A person who studies the Earth, which includes all the rocks, is called a geologist, and this type of science is called geology. Geologists look at the structure of our Earth, how it was made, and how it has changed over time. They examine valleys, mountains, rivers, and lakes to understand how they came to be.
Geologists study things like rocks, landslides, earthquakes, volcanoes, and many other elements of the Earth. They also explore the interaction between humans and the planet, learning ways that the Earth and humans can support each other so that we do not run out of natural resources. It’s important that we study the Earth so that we know how it has changed or could change over time and what we can do to help keep it sustainable. Sustainable means we are trying to keep something working for a long time.
Today, we will focus on just one job of a geologist: studying rocks. You have probably looked at many rocks in your lifetime. Even though they may look alike, rocks are not all the same. The type of each rock is determined by how the rock formed over time. There are three main types of rocks: sedimentary, metamorphic, and igneous.
**Sedimentary Rocks**
A sedimentary rock is formed from particles of sand, shells, pebbles, and other pieces of material. All these particles together make up something called sediment. Sediment is the result of material broken down by weathering or erosion. If you break apart a rock, the small pieces of dust from that rock become sediment. Sedimentary rocks are soft, crumble easily, and are made up of other tiny rock pieces. Over long periods, sediment gets pressed into more sediment, which creates layers. Eventually, all those layers harden, making a rock. Sedimentary rocks are usually the only type of rock that contains fossils, which are imprints of dead animals or plants from long ago. Examples of sedimentary rocks include limestone, shale, sandstone, chalk, and more.
**Metamorphic Rocks**
Metamorphic rocks are formed under the surface of the Earth. It takes millions of years, as well as intense heat and pressure, for a metamorphic rock to be formed. The rocks that result from this very long process often have ribbon-like layers and many shiny crystals in them. The crystals are formed by minerals that grow slowly over time on the surface of the rock. You might even eat your breakfast off a metamorphic rock each morning! Common metamorphic rocks include marble, slate, and quartz, which are often used for kitchen, bathroom, and other countertops. If your countertop is made of a metamorphic rock, take some time to study that slab of rock and see if you can see the layers of crystals in it.
**Igneous Rocks**
Igneous rocks form when magma cools and hardens. Magma is molten rock deep within the Earth; it’s the material inside a volcano. Sometimes this magma cools inside the Earth; other times, it erupts onto the surface of the Earth from a volcano. When magma leaves the volcano, it is called lava. Lava cools very quickly, and when it does, the rocks it creates look shiny and glass-like. Sometimes gas bubbles get trapped inside the rock during the cooling process, leaving tiny holes and spaces inside the rock.
Igneous rocks are divided into two groups: intrusive igneous and extrusive igneous. Intrusive igneous rocks, sometimes called plutonic rocks, are formed when magma slowly cools inside the Earth over a long period of time. Since they cool very slowly, it allows large crystals to form inside of them. Granite is an example of this type of rock. You’ve probably seen granite before; many countertops are made of granite too. On the other hand, extrusive igneous rocks are formed when molten lava cools very quickly on the surface of the Earth. Because these rocks cool very fast, it doesn’t leave much time for crystals to form. Rocks like basalt, andesite, and pumice result from this process. Sometimes the lava cools so fast that no crystals form at all, and obsidian rock is formed. That’s a beautiful rock!
**Ready for a Little Review?**
Let’s get rockin’!
– **True or False:** Geologists study the Earth.
– **True**
– **What are the three different kinds of rocks?**
– Sedimentary, metamorphic, and igneous.
– **True or False:** There’s only one type of igneous rock.
– **False** (There are two types: intrusive and extrusive.)
– **Fill in the blank:** Marble is a type of ______ rock.
– Metamorphic.
– **What’s one example of a sedimentary rock?**
– Limestone, shale, sandstone, chalk.
Well done, everybody! We’ve put our geologist hats on and learned that not all rocks are the same. They have different characteristics and processes that shape how they are made. Remember that sedimentary rocks are soft and crumble easily, metamorphic rocks are layered, dense, have shiny crystals in them, and are made deep inside the Earth, and igneous rocks are volcanic, shiny or glass-like, and they might have tiny holes or spaces in them. Keep being a geologist! The next time you pick up a rock, inspect it closely and decide if it’s sedimentary, metamorphic, or igneous. Doesn’t geology rock?
