Are all rocks the same? No way! Rocks can be different shapes, sizes, textures, and colors. There are 3 different types of rocks that can affect what a rock looks and feels like. The three types of rocks
are sedimentary, igneous, and metamorphic.
Sedimentary rocks are a mixture of dirt, rocks, mud, shells, and other materials that are on the bottoms of oceans and other bodies of water, and get compacted together over many years. Sometimes you can even see different layers in sedimentary rocks. These types of rocks feel grainy, like sand, and are easier to crumble than other types of rocks. Sometimes sedimentary rocks will have plant or animal imprints!
The second type of rock is the igneous rock. These rocks are created from magma that cools and hardens. Many rocks start out as igneous rocks.
Igneous rocks have glass crystals filled with minerals in them. They do not usually have layers, and are very smooth.
The third type of rock is the metamorphic rock. These rocks are formed when the other types of rocks are subjected to intense heat and pressure to change them. Metamorphic rocks are hard and smooth, like igneous rocks.
Just like plants and animals have a life cycle, rocks can go through a rock cycle! Many rocks start from magma or lava, so they are igneous rocks.
The igneous rocks could get broken up in a river or stream and settle to the bottom of a lake. Over thousands or millions of years, the broken up rocks could get compacted into a sedimentary rock. The sedimentary rock could get exposed to intense heat, and change to a metamorphic rock. Then the metamorphic rock could get covered by many other rocks and end up deep in Earth’s crust. It may melt and turn into magma, and the cycle could start over again. The rock cycle is different than a life cycle of a plant or animal, though, because a rock doesn’t have to go through the cycle in order, and it may not go through all the stages.
Even though there are only three different types of rocks based on how they’re formed, each type actually has many different subcategories of rock. For example obsidian, granite, and basalt are three types of igneous rocks. This is why there are so many different colored rocks. Many people love to collect rocks because of how different each one can be.
Answer each question:
1. What are sedimentary rocks? Highlight the sentence that has the
answer.
2. What are the three types of rocks?
3. How are life cycles and the rock cycle different?
4. Do you think all sedimentary rocks look the same? Why or why not? Support your answer with evidence from the passage.
5. What else do you wonder about rocks after reading the passage?
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