Rocks and Earth Materials
Earth's surface is made of rocks and minerals that form through different processes and can be classified by their properties and origins.
What You Need to Know
Key Concept Diagram
Igneous rocks form when magma (molten rock) cools and solidifies; they can be intrusive (granite) or extrusive (basalt)
Sedimentary rocks form when layers of sediment are compressed over time; they often contain fossils (e.g. sandstone, limestone)
Metamorphic rocks form when existing rocks are changed by heat and pressure deep inside the Earth (e.g. marble, slate)
The rock cycle describes how rocks are continuously transformed from one type to another over millions of years
Key Vocabulary
Igneous rock
Rock formed from cooled and solidified magma or lava
Sedimentary rock
Rock formed from compressed layers of sediment such as sand, mud, or shells
Metamorphic rock
Rock that has been changed by extreme heat and pressure within the Earth
Rock cycle
The continuous process by which rocks are formed, broken down, and reformed over time
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
Which type of rock is most likely to contain fossils?
Question 2
Marble is formed when limestone is subjected to extreme heat and pressure. What type of rock is marble?
Question 3
Lava from a volcanic eruption cools quickly on the Earth's surface. What type of rock does it form?
Key Concepts Summary
- ●Igneous rocks form when magma (molten rock) cools and solidifies; they can be intrusive (granite) or extrusive (basalt)
- ●Sedimentary rocks form when layers of sediment are compressed over time; they often contain fossils (e.g. sandstone, limestone)
- ●Metamorphic rocks form when existing rocks are changed by heat and pressure deep inside the Earth (e.g. marble, slate)
- ●The rock cycle describes how rocks are continuously transformed from one type to another over millions of years