1. Rocks!!!
Ch. 3

2. What is a rock?
Any solid mass of mineral or mineral-like matter that occurs naturally as part of our planet
3 types
Igneous
Sedimentary
Metamorphic
Do you think that the minerals we need in our diets are the same as the minerals that make rocks? No, rock minerals are naturally occurring inorganic minerals
What does the word Sedimentary tell you about how the rock is formed?

3. The rock cycle
Interactions among Earth’s water, air, land, and living things can cause rocks to change from one type to another
A continuous process

4. Igneous Rocks Forms when lava or magma hardens. Lava: Magma:
Molten rock on the surface of the Earth
Magma:
Molten rock beneath Earth’s surface.

5. Igneous Rock Formation
Igneous rocks are formed by the cooling of molten rocks and the crystallization of minerals.

6. Types of igneous rocks
Intrusive Igneous rock: forms when magma hardens beneath Earth’s surface
Extrusive Igneous Rock: forms when lava hardens on the surface of the Earth

7. Classifying igneous rocks
Igneous Rocks are classified based on their texture and composition.

8. Texture classification
Texture: size, shape, and arrangement of interlocking crystals.
Course Grained: slow cooling, large crystals.
Fine Grained: rapid cooling, small interconnected mineral grains.
Glassy: looks like glass, extrusive igneous rocks. Ex. Obsidian
Porphyrite: large crystals embedded in a matrix of much smaller crystals.

9. Composition classification
Composition: based on proportions of light to dark minerals
Basaltic Composition
Contains many dark silicates minerals and plageoclase feldspar
Rich in magnesium and iron
Ex: basalt and gabbro
Granitic Composition
Made almost entirely of light-colored silicate minerals like quartz and feldspar
0 to 25% dark minerals
Biotite and amphibole

10. Composition classification
Andesitic Composition
Between basltic and granitic composition
At least 25% dark minerals
Ultramafic Composition
Composed mainly of iron and magnesium rich mineral
Almost entirely dark minerals

11. Igneous chart Composition and Texture Granite Andesitic Basaltic
Ultramafic
Coarse
Diorite
Gabbro
Peridotite
Fine
Phyolite
Andesite
Basalt
Kematite
Porphyritic
Inside any given rock
Uncommon
Glassy
Obsidian, Pumice

12. What is a Sedimentary rock?
Forms when existing rocks are broken down into sediment then compacted and cemented together
Processes
Cementing
Compaction

13. How do they form?
Weathering: Any process that break rocks into sediments
Erosion : The removal of weathered rocks
Deposition: when an agent of erosion (water, wind, ice, or gravity) loses energy, it drops the sediment
Compaction: is a process that squeezes or compacts sediments together
Cementation: takes place when dissolved minerals are deposited in the tiny spaces among the sediments

14. Classification of sedimentary rocks
Classified by the way they form
Clastic or chemical

15. Clastic sedimentary rocks
Made of weathered bits of rocks and minerals
Grouped according to the size of the sediment.

16. Clastic sedimentary rocks
Texture
Sediments
Name of Rock
Coarse
(over 2 mm in size)
Gravel - rounded
Conglomerate
Gravel- angular
Breccia
Medium (2mm to 1/6 mm)
Sand
Sandstone
Fine (1/16 to 1/256 mm)
Silt
Siltstone
Very Fine (< 1/256 mm)
Mud
Shale/mudstone

17. Chemical sedimentary rocks
Form when dissolved minerals precipitate from water solution
Biochemical Sedimentary Rock: made from once living organisms (like shells and skeleton remains)
Ex: limestone, chalk, conquina, rock salt, and bituminous coal

18. What is a metamorphic rock?
Form when existing rocks are changed by heat and pressure Metamorphism: means “change form”

19. What causes metamorphism?
Heat: provides the energy needed to drive chemical reactions which causes existing minerals to recrystallize Pressure: applied in all directions on a rock which causes spaces between mineral grains to close Hydrothermal Solutions: hot, water based solutions that promote recrystallization by dissolving original minerals and then depositing new ones

20. Classification of Metamorphic Rocks
Classified by texture and composition
Foliated
Rock with layered or banded appearance
Ex: Gneiss
Nonfoliated
No layered or banded appearance
Contains only one mineral
Ex: Marble

21. Classification of foliated metamorphic rocks
Name
Texture/Grain Size
Parent Rock
Slate
Very fine
Shale, mudstone
Phyllite
Fine
Schist
Medium to course
Gneiss
Coarse
Schist, granite

22. Classification of non-foliated metamorphic rocks
Name
Texture/grain size
Parent rock
Marble
Medium to coarse
Limestone
Quartzite
Quartz, sandstone
Anthracite
Fine
Coal