1. Rocks

2. How Rocks Form
Using color, texture, and mineral composition, geologists can classify a rock according to its origin (how it was formed)
Geologists classify rocks into three major groups:
Igneous
Sedimentary
Metamorphic

3. Igneous Rocks

4. What is an Igneous Rock? Any rock that forms from magma or lava
Three ways to classify
Origin
Texture
Mineral composition

5. Origin May form ON or BENEATH Earth’s surface
Extrusive rock – igneous rock formed from lava that erupted onto Earth’s surface
Think “exterior” – meaning on the outside
Example – Basalt
Intrusive rock – igneous rock formed when magma hardened beneath Earth’s surface
Think “interior” – meaning on the inside
Example - Granite

7. Texture cont… Extrusive & Intrusive Rocks have different textures
Intrusive = larger crystals/ coarse grained
Extrusive = small crystals/fine grained or glassy

8. Mineral Composition Lava low in silica = dark colored rock
Magma high in silica = light colored rock
The formula for silica is: SiO2 (Silicon + Oxygen)

9. Uses of Igneous Rocks Largely used for tools and building materials
Statues
Bridges
Paving streets
Counter tops
Good for cleaning
pumice

10. Sedimentary Rock

11. What is a sedimentary rock?
Sediment – small, solid pieces of material that come from rocks or living things
may include shells, bones, leaves, stems
Formed when sediment is deposited by water and wind
Formed through a series of processes
1. erosion
2. deposition
3. compaction
4. cementation

12. 1. Erosion Forces constantly weathering rocks on earth’s surface
Heat, cold, rain, waves, grinding ice
Forces form sediment
In Erosion (1) running water, or ice loosen and carry away fragments of rock 1

13. 2. Deposition
Moving water, wind, or ice slow and deposit sediment into layers
Sediment will sink to bottom
Deposition (2) is process by which sediment settles out of the water or wind carrying it 2

14. 3. Compaction
Compaction (3) – the process that presses sediments together
Thick layers eventually build up
Heavy layers press down on layers beneath
Weight of new layers further compacts sediments, squeezing them tighter together
Layers remain visible in rock 3

15. 4. Cementation
While compaction occurring, minerals in rock slowly dissolve in water
Cementation (4) – process in which dissolved minerals crystallize and glue particles of sediment together
Dissolved minerals seep into the spaces between particles then harden 4

16. Types of Sedimentary Rock

17. Organic Sedimentary Rock
Form where the remains of plants and animals are deposited in thick layers
“organic” = once living

18. Chemical Sedimentary Rock
Chemical rocks form when minerals are dissolved in a solution and crystallize

19. Uses for Sedimentary Rock
Building materials
Cement
steel
Tools
Arrow heads

20. Metamorphic Rocks

21. What is a Metamorphic Rock?
EVERY metamorphic rock is a rock that has changed its form
HEAT and PRESSURE deep beneath Earth’s surface can change any rock into metamorphic rock (MR)
When rock changes into MR its appearance, texture, crystal structure, and mineral content change
Can form out of igneous, sedimentary or metamorphic rock

22. How can the rocks change?
Collisions between Earth’s plates can push rock down toward heat of mantle
Pockets of magma rising through crust provide heat
Deeper rock is buried in crust, greater the pressure
When under great pressure and temperature, minerals in rock can be changed creating a metamorphic rock

23. Types of Metamorphic Rock
Foliated Rocks
Grains arranged in parallel layers or bands
May split apart along bands
Example
Shale  Slate

24. Types of Metamorphic Rock cont…
Nonfoliated rocks
Grains arranged randomly
Do not split into layers
Example
Sandstone  Quartzite

25. Uses of Metamorphic Rock
Building
Flooring
Roofing
walkways
Sculpture
Use marble (Lincoln Memorial)

26. The Rock Cycle What is it?
Forces deep inside the earth and at the surface produce a slow cycle that builds, destroys, and changes the rocks in the crust