1. Rocks
Chapter 4

2. What is a rock?
Rock
Mixture of minerals, rock fragments, volcanic glass, organic material, or other natural materials.

3. What is a rock?
Rock Cycle
Cycle that demonstrates the three types of rock and the processes that create and change them.

4. What is a rock?
Matter and the Rock Cycle
Changes that occur in the rock cycle never create or destroy matter.
Elements that form the rocks are simply redistributed.

5. Formation of Igneous Rocks
Form when magma cools and hardens.

6. Formation of Igneous Rocks
Magma
Forms when heat and pressure in the interior of the earth melt rock.
Temps of magma range from 650 to 1200 degrees Celsius
Because magma is less dense than surrounding solid rock it is forced upward.
Magma that has erupted to the surface of the earth is called lava.

7. Formation of Igneous Rocks
Intrusive Rocks
Igneous rocks that form beneath the surface of the earth.
Cool very slowly which results in large mineral grains (coarse-grained).

8. Formation of Igneous Rocks
Extrusive Rocks
Form when lava cools on the surface of the earth.
Cool rapidly resulting in small mineral grains (fine-grained).
Volcanic glass is a type of extrusive igneous rock with no to few mineral grains
Very rapid cooling

9. Classifying Igneous Rocks
Classification
Classified as intrusive or extrusive
Classified into three families based on composition of magma from which they formed.
Basaltic
Granitic
Andesitic

10. Classifying Igneous Rocks
Basaltic Rocks
Dark-colored, dense
Form from magma low in silica and high in magnesium and iron
Examples: Hawaii, moon

11. Classifying Igneous Rocks
Granitic Rocks
Light-colored, lower density
Form from magma rich in silica

12. Classifying Igneous Rocks
Andesitic Rocks
Form from magmas in between felsic (granitic) and mafic (basaltic).

13. Metamorphic Rocks Metamorphic Rocks
Rocks that have been changed by high temperature, high pressure, or hot fluids.
The rock from which the metamorphic rock formed is called the parent rock.

14. Classifying Metamorphic Rocks
Classification
Classified according to mineral composition and texture.
Foliated
Mineral grains of the rock are arranged in parallel layers.
Nonfoliated
Mineral grains of the rock are not arranged in layers.

15. Formation of Sedimentary Rocks
Form when sediments are pressed and cemented together or when minerals form from solution.
Sediments are loose materials such as rock fragments, mineral grains, and organics (bits of shell, etc).
Come from rock that has been eroded.

16. Classifying Sedimentary Rocks
Classification
Classified by the type of sediments in the rock and how the rock formed.
Detrital
Chemical
Organic

17. Detrital Sedimentary Rocks
Formation
Formed from pieces of other rock that have been compacted or cemented together.
When exposed to the air, water, and wind rock is broken down through the process of weathering.
Sediments can be moved through erosion to new locations where they are deposited.

18. Detrital Sedimentary Rocks
Compaction
As sediments are deposited, sediment layers on top put pressure on sediment layers below them, eventually pressing the sediments into rock.

19. Detrital Sedimentary Rocks
Cementation
As water moves through rocks, minerals are dissolved in the water.
The water carries the dissolved minerals through cracks in rock.
These minerals (such as quartz, calcite, or hematite) can be deposited between pieces of sediment, cementing them into rock.

20. Detrital Sedimentary Rocks
Further classification
Detrital sedimentary rocks are further classified by the shape and size of sediments that form them.

21. Chemical Sedimentary Rocks
Formation
Form when dissolved minerals come out of solution.
Limestone
Calcium carbonate is dissolved in ocean water and precipitates out as calcite, forming limestone.
Rock Salt
Water rich in salts leave the mineral halite when the water evaporates, forming deposits of rock salt

22. Organic Sedimentary Rocks
Formation
Rocks that are made from the remains of once living things
Fossil-rich limestone
Chalk
Consists of microscopic shells.
Coal
Formed from plant remains buried in swamps.
The plant remains are changed into coal by microscopic organisms and pressure.