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Rock Types

Author: Mary MacDonald


These are some definitions that you may want to remember from class that will help you with understanding this lesson

  • Magma- molten liquid state of rock
  • Lava- magma that rises to earths surface
  • Sediments- a bunch of mineral particles formed by weathering of rocks, that are found at low areas that are under pressure
  • Compaction - pressure from layers that lie above
  • Cementation- binding of particles by precipitation of dissolved minerals which act like glue
  • Precipitation - separation of solids from a solution

3 Types of Rocks

Rocks come in many size, shapes, and colors! No two rocks are the same and many people like to collect rocks. There are three types of rocks that geologist like to classify by the way that they were formed.

  • Igneous
  • Sedimentary
  • Metamorphic

Igneous Rock Formation

Igneous rocks form when magma or lava cools.
There are two types of Igneous rocks
-These igneous rocks form below earths surface and the magma cools slowly. This leads to the rocks having larger mineral crystals.
- These igneous rocks form from molten rock that is ejected from volcanos and then it cools rapidly at earths surface. This leads to the rocks having small mineral crystals.

Sedimentary Rock Formation

Sedimentary rocks are formed from compaction and cementation of sediments. This video helps to explain the process in a simple way.

Metamorphic Rock Formation

Metamorphic rocks are rocks that are transformed by heat and pressure deep underground. The rocks go through bending, compression, and streching. They are not completely melted back into magma. An example of this would be slate or marble.

Rock Cycle

The rock cycle is the slow transformation of rocks by heating, melting, cooling, breaking down, and reassembling. Any type of rock, through a process, can become any other type of rock. A rock is any solid arrangement of minerals.

Click on the picture above to explore a website that will help further explain the rock cycle!

Rock Cycle

Here is a short video that helps to visualize the rock cycle!

Overview Assessment

Take this short quiz to see if you understood the concepts taught in this lesson.


The rock cycle is a model of creation and transformation of rocks from one form (sedimentary, igneous, or metamorphic) to another. Rock families are determined by the origin and transformations of the rock.


Distinguish physical properties of sedimentary, igneous, or metamorphic rocks and explain how one kind of rock could eventually become a different kind of rock.