HW
52
NAME:
DATE:
SECTION:
Reading About Rock Types
DIRECTIONS: Read the article and follow these instructions:
 Before you read, you should look at the questions that are at the end of the
article. Keep the questions in mind so that you can find the answers as you are
reading.
 While you are reading, use a highlighter to highlight the areas of the article where
you found the correct answers to the questions.
 After you read, use full sentences to answer the questions.
There are three main types of rocks:
Sedimentary rocks are layers of rock fragments that were compressed and cemented together.
They often contain fossils.
Sedimentary rocks are formed when eroded1 fragments of old rocks and dead organisms2 settle
(usually in seas or rivers) to form what is called sediment. Over millions of years, layers of
sediment build up and are buried one on top of the other. They are compressed3, and their weight
squeezes out the water. Eventually the pieces of rock in the sediment become stuck together to
form sedimentary rocks.
Sedimentary rocks have a layered appearance. They may contain fossil remains of animals and
plants that were trapped as the rocks formed. These fossils can be used to tell how old the rock is.
Limestone, sandstone and mudstone are examples of sedimentary rocks.
Eroded: broken up
Organisms: living things
3 Compressed: pressed together
1
2
TURN OVER
Igneous rocks are molten rock (called magma) that cools and solidifies. They do not contain
fossils.
Igneous rocks contain randomly4-arranged crystals. The crystals are large if the molten rock cooled
slowly, and small if it cooled quickly.
Granite and basalt are examples of igneous rocks.
Metamorphic rocks are formed when igneous or sedimentary rocks are compressed and heated
without melting. This often happens at the edges of tectonic plates, where there are very high
temperatures and pressures as mountains are being formed.
Metamorphic rocks usually contain regularly-aligned5 crystals, and they may be shiny and hard.
They sometimes flake into layers.
Marble, slate, and gneiss are examples of metamorphic rock.
4
5
Random: not in any kind of order
Aligned: in a line
HW
52
NAME:
DATE:
SECTION:
QUESTIONS:
Make sure you answer in a complete sentence!
1. There are three types of rocks. What are they?
2. What two types of rocks are formed by smaller bits of rock being compressed?
3. What type of rock is formed from sediment?
4. What type of rock can contain pieces of dead organisms?
5. What two types of rocks contain crystals?
6. Which type of rock contains regularly-aligned crystals?
7. Metamorphic rocks can be made from two other types of rocks. What are they?
8. Give three examples of sedimentary rock.
9. Give two examples of igneous rock.
10.
Give three examples of metamorphic rock.