1. The Rock Cycle Igneous Rocks Metamorphic Rocks Sedimentary Rocks

2. WHAT IS A ROCK? Rocks are classified as mixtures.
They are mixtures of:
Minerals
Mineraloids
Glass
Organic matter

3. THE ROCK CYCLE The rock cycle shows how one rock changes into another.
The following are processes that change rocks.
Weathering
Erosion
Compaction
Heat & pressure
Cementation
Melting
Cooling

4. THE ROCK CYCLE

5. IGNEOUS ROCKS (Latin ignis meaning “fire”)
Most abundant type of rock on Earth
Magma and lava cool to form igneous rocks
Magma = melted rock below the Earths surface
Lava = melted rock on the surface of the Earth
You classify igneous rock by where it formed (intrusive or extrusive) and by the types of minerals in them.
An igneous rock can be either basaltic, granitic or andesitic

6. INTRUSIVE IGNEOUS ROCKS
Magma is insulated deep inside the Earth so it cools slowly.
When magma cools slowly the atoms have time to arrange into large crystals called mineral grains
Example of intrusive rocks:
Gabbro
Diorite

7. EXTRUSIVE IGNEOUS ROCKS
Lava is on the Earth’s surface so it cools fast.
The quick rate of cooling keeps large mineral grains from forming.
Often the individual grains are too small to be seen without magnification.
Example of extrusive rocks:
Obsidian – smooth glass
Pumice & scoria – glass with holes or pockets that formed as air & other gasses escaped the cooling rock

8. BASALTIC IGNEOUS ROCKS
Form from basaltic magma or lava
Dense,heavy, dark colored rocks
Rich in iron and magnesium
Flow from volcanoes in Hawaii
Does this help explain the black sand beaches of Hawaii?

9. GRANITIC IGNEOUS ROCKS
Granitic magma and lava are thick, stiff & contain a lot of silicon and oxygen
Light-colored rock
Lower density than basaltic rock
Granitic magma builds up a lot of pressure that is released during violent volcanic eruptions

10. ANDESITIC IGNEOUS ROCKS
Mineral composition between those of basaltic and granitic rocks
Many volcanoes in the Pacific ocean are andesitic

11. METAMORPHIC ROCK
Rocks that have changed due to temperature & pressure and/or changes in composition
Can be formed from changes to igneous, sedimentary or other metamorphic rocks.
Ex: Grains in granite get flattened and line up when pressure is applied to them forming gneiss
Ex: Grains in shale are arranged into layers when heat and pressure is applied forming slate

12. SEDIMENTARY ROCKS
Form when sediments become pressed or cemented together or when sediments precipitate out of solution.
Erosion moves sediments to a new location
Layer upon layer of sediment build up
Pressure from the upper layer pushes down
If sediment is small they stick together to form solid rock
If sediment is large the pieces get cemented together by minerals dissolved in water

13. CLASSIFICATION OF SEDIMENTARY ROCKS
Clastic – made up of broken fragments of rock, plants or animals
Conglomerate (round sediments) & Breccia (sharp angled sediments) form from large sediments
Chemical – form from minerals precipitated out of solution or left behind from evaporation. Ex: rock salt
Organic – rock form from once living things Ex: fossil-rich limestone (writing with chalk is smearing calcite shells of once living animals)

14. Chapter 4 QUIZ Where are Igneous rocks formed?
How are Metamorphic rocks formed?
How are sedimentary rocks formed?
What is the difference between the formation of intrusive and extrusive Igneous rocks?

15. Answers Please!

16. Chapter 4 QUIZ How are Igneous rocks formed?
In magma or lava
How are Metamorphic rocks formed?
A change takes place
How are sedimentary rocks formed?
Build up of sediments that get compressed
What is the difference between the formation of intrusive and extrusive Igneous rocks?
Intrusive - formed inside volcano in magma
Extrusive - formed outside volcano in lava