Rocks are a mixture of one or more minerals , glass, or organic material that makes up the Earth’s surface.

1. Rocks Rocks are a mixture of one ormore minerals, glass, or organic material that makes up the Earth’s surface.

2. Classifying Rocks • When studying a rock sample, geologists observe the rock’s color, texture, and determine its mineral composition.

3. Texture and Grain Size Texture- the look and feel of the rock’s surface ( smooth, glassy, rough, chalky) • Grains ( particles of minerals or other rocks) give the rock its texture. • Grain size-fine or coarse grained • Grain shape- ex. Small seeds, shooting stars • Grain pattern-grains • form a pattern • No visible grain- rocks have glassy texture

4. Mineral Composition and Origin • Mineral Composition- geologists look under a microscope to see what minerals a rock contains (test w/ acid, test w/ magnet) • Origin- There are 3 major groups of rocks: igneous, sedimentary, & metamorphic. Depending on which type depends on how it formed.

5. The Rock Divisions • Rocks are classified by how they formed and what they’re made of • There are 3 general classes of rocks • Igneous Rocks…are formed when lava and magma crystallize to form solid rock • Metamorphic Rocks…are formed when an existing rock is partially melted, squeezed, or both • Sedimentary Rocks…are formed when sediments (sand clay, and silt) are compressed and become solid rock

6. How Rocks Form • Geologists classify rocks into three major groups: igneous rock, sedimentary rock, and metamorphic rock.

7. Igneous Rocks • Any rock that forms from magma or lava is an Igneous rock. These rocks are the most abundant rock on Earth. "Fire Rock"

8. Classifying Igneous Rocks • Igneous rocks are classified according to their origin, texture, and mineral composition.

9. Two Types of Igneous Rocks • Extrusive Rock- forms from lava that erupts onto Earth’s surface. • Very small mineral grains • Ex. Basalt, and andesite • Intrusive rocks- forms when magma hardens beneath Earth’s surface. • Large mineral grains • Ex. Granite, and grabbo

10. Mineral Mixture • Granite is a mixture of light-colored minerals, such as feldspar and quartz, and dark-colored minerals, including hornblende and different types of mica. But granite can vary in mineral composition. This affects its color and texture. • Study the circle graph and then answer the questions.

11. Feldspar What mineral is most abundant in granite? Mineral Mixture

12. 10% About what percentage of granite is made up of dark minerals? Mineral Mixture

13. Texture of Igneous Rocks • Texture- depends on the size and shape of the igneous rocks mineral crystals. May be fine grained, coarse grained, glass, or porphyritic. • Rapid cooling- fine grained with small crystals • Slow cooling- coarse grained with large crystals • Porphyritic texture- a rock with large crystals scattered on a background of much smaller crystals. Forms when intrusive rocks cool in two stages.

14. Sedimentary Rocks • Form from particles deposited by water and wind that are pressed together.

15. From Sediment fo Rock • Most sedimentary rocks are formed through a series of processes: erosion, deposition, compaction, and cementation.

16. Formation of sedimentary rocks

17. Formation of sedimentary rocks • Erosion- running water or wind loosen and carry sediments away. • Deposition- the process by which sediment settles out of the water or wind carrying it.

18. Formation of sedimentary rocks • Compaction- the process that presses sediments together. • Cementation- process in which dissolved minerals crystallize and glue particles of sediments together.

19. Types of sedimentary rocks • Clastic rocks- forms when rock fragments are squeezed together. You can see the layers like a layer cake or the bits & pieces of smaller rock cemented together. • Organic rocks- forms where the remains of plants and animals are deposited in thick layers. ( fossils and coal) • Chemical rocks- when minerals that are dissolved in a solution crystallize. Ex.- rock salt

20. Sedimentary Transformations • Point A: water or wind deposits sediments • Point B: The heavy sediments press down on the layers beneath • Point C: Dissolved minerals flow between the particles and cement them together

21. Rocks that have changed due to heat and pressure. • How does metamorphic rocks form? • The deeper the rock is buried in the crust, the great the pressure on that rock. Under pressure thousands of times greater than Earth’s surface, the minerals in a rock can change into other minerals. Metamorphic Rocks

22. Forming Metamorphic Rocks Great heat and pressure can change one type of rock into another. How does slate differ from shale?

23. Classifying Metamorphic Rock • Foliated rock- rocks that have their grains arranged in parallel layers or bands. Example- gnesis & slate • Non-foliated rock- do not form bands. It is composed mostly of the same mineral. Ex. Quartzite and marble

24. Rock Cycle – A Cycle of Many Pathways Forces deep inside Earth and at the surface produce a rock cycle that builds, destroys, and changes the rocks in the crust.

25. Another Rock Cycle Picture

26. And Another Rock Cycle Picture

27. A Rocks Concept Map Metamorphic Igneous Organic Foliated Extrusive Chemical