1. Chapter 6 Rocks

2. Three Major Types of Rock
Igneous Rock
When magma (molten rock inside Earth) cools and hardens
Lava (molten rock exposed at the Earth’s surface

3. Three Major Types of Rock
Sedimentary Rock
The products of erosion (small rocks, mineral fragments, organic matter) are called sediment.
Sediments carried and deposited by water, ice and wind.
Sediment compressed and cemented together = sedimentary rock.

4. Three Major Types of Rock
Metamorphic rock
When rock subjected to high pressure, temperature and chemical processes, the original form changes = metamorphic rock

5. Rock Cycle

6. Bowen’s Reaction Series
Explains the order that minerals form when magma solidifies. g

7. Properties of Rocks Chemical Stability of Minerals:
The rate at which a mineral chemically breaks down depends on the chemical stability of the mineral.
Chemical stability is a measure of the tendency of a chemical compound to maintain its original chemical composition.

8. Properties of Rocks Physical stability of rocks
Rocks have natural zones of weakness that are determined by how and where the rocks form.
Example: Sedimentary rocks may break along layers. Metamorphic rocks tend to break there minerals are aligned in the rock. Igneous rocks have joints (zones of weakness)

9. Igneous Rocks
Because minerals crystallize as magma cool, igneous rocks are identifies as crystalline.
The chemical composition of mineral and the rock’s texture determine the identity of the rock.

10. Formation of Magma
Magma forms when rock melts. Three factors affect whether a rock melts: temperature, pressure and the presence of fluids in the rock.
The melting temperature is determined by the chemical composition of the minerals in the rock, as wells as pressure and fluids.

11. Magma Formation
Partial Melting: Different minerals have different melting points, and minerals that have lower melting points are the first minerals to melt.
As the temperature increases and as other mineral melt, the magma’s composition changes = partial melting

12. Magma Formation Fractional Crystallization
When magma cools, the process is the reverse of the partial melting.
As crystals form, certain minerals are removed from the magma = fractional crystallization
Crystals the form first, tend to be larger because they have more time to form.

13. Textures of Igneous Rocks
Intrusive igneous rocks: Rocks that form deep inside the crust and cool slowly.
Coarse-grained texture because the crystals have time to form.
Extrusive igneous rocks: Rocks that form on the surface and cool very quickly.
Fine-grained texture because cooled quickly

14. Textures of Igneous Rocks
Other textures:
Porphyritic texture: Mixture of large and small crystals because of different rates of cooling.
Glassy texture: When thick magma cools quickly and few crystals are able to grow. (Obsidian)
Vesicular texture: When magma full of gasses and cools quickly, get a rock full of holes. (pumice, lava rock)

15. Composition of Igneous Rocks
Three families of igneous rocks:
Felsic Rock: Where the originating magma contains a large proportion of silica
Mafic Rock: Where the originating magma contains a lower proportion of silica and is rich in iron and magnesium.
Intermediate Rock: Falls in the middle of the two

16. Intrusive Igneous Rock Structures
Batholiths and Stocks
Laccoliths
Sills and Dikes

17. Extrusive Igneous Rock Structures
Volcanoes
Volcanic Necks
Lava flows and plateaus

18. Sedimentary Rocks
Sediment: Loose fragments of rock, minerals, and organic material.
Once eroded, transported by wind, water, or ice to new location and deposited.

19. Sedimentary Rocks
Compaction: Where sediment is squeezed and size of the pore space between sediment grains is reduced.
Cementation: Where sediments are glued together by minerals that are deposited by water moving through the sediment.

20. Sedimentary Rocks Three main types of sedimentary rocks:
Chemical: Where dissolved minerals precipitate out of solution. Water evaporates and the minerals become too concentrated.
Examples: Evaporites like gypsum and halite.

21. Sedimentary Rocks Three main types of sedimentary rocks:
Organic sedimentary rock: Forms from the remains of living things.
Examples: Coal forms from plant remains that are buried before they decay and are compacted.
Limestone: Marine organisms remove the minerals from seawater and make their shells. When they die, their shells become limestone.

22. Sedimentary Rocks Three main types of sedimentary rocks:
Clastic Sedimentary Rock: Made up of rock fragments.. Are classified according the size of their particles.
Conglomerate: Rounded rocks are cemented together by finer fragments.
Breccia: Sharp angled fragments cemented together by finer fragments.

23. Sedimentary Rocks Three main types of sedimentary rocks:
Sandstone: Usually quartz fragments are cemented together to make sandstone. Usually has pore space between pieces so fluids can move through.
Shale: Clay-sized particles are cemented and compacted. Because clay particles are flat and pressed into layers, not usually porous.

24. Sedimentary Rocks Characteristics of Clastic Sediments:
Sorting: Where wind or water separate sediments according to size.

25. Sedimentary Rocks Characteristics of Clastic Sediments:
Angularity: The further the sediment travels from its source, the finer and smoother the particles of sediment become

26. Sedimentary Rocks Sedimentary Rock Features
Stratification: Occurs when the conditions of sedimentation deposition change. Either different sediment type, or the environment changes like changes in sea level

27. Sedimentary Rocks Sedimentary Rock Features
Cross-beds and Graded Bedding: Slanting layers which form in sand dunes or river beds or layers of different size grains.

28. Sedimentary Rocks Sedimentary Rock Features
Ripple marks: Actions of wind or water on sand is preserved.
Mud Cracks

29. Sedimentary Rocks Sedimentary Rock Features
Fossils: Where either an impression is left or the fossil fills in the shell.
Concretions: Areas where minerals fill in a cavity

30. Metamorphic Rocks
Metamorphic Rocks: Form when heat, pressure, and hot fluids cause some minerals to change into other minerals.
Two Types:
Where small volumes of rock come into contact with magma.
Large areas of crust are affected by heat and pressure of tectonic plates.

31. Metamorphic Rocks
Contact Metamorphism: Heat from magma can change the structure and mineral composition of surrounding rock.

32. Metamorphic Rocks
Regional Metamorphism: During periods of tectonic movement, large areas of crust are exposed to heat and pressure. Heat and pressure change the composition of the pre-existing rock.

33. Metamorphic Rocks Classification of Metamorphic Rocks
Foliated Rocks: A rock texture in which minerals are arranged in plates or bands called foliations.
Slate: When shale is metamorphosed and the minerals are compressed into thin layers.
Schist: Where slate is further met. Due to intense heat and pressure.
Gneiss: A schist in which the minerals have separated into dark and light bands.

34. Metamorphic Rocks Classification of Metamorphic Rocks
Non-Foliated: Rocks that do not have bands or aligned minerals BECAUSE:
The original rock may contain only one minerals or contains only small amounts of other minerals OR
The original rock does not have long grains so do not change position when exposed to pressure in one direction.

35. Metamorphic Rocks Classification of Metamorphic Rocks
Examples of non-foliated metamorphic rocks:
Quartzite: Metamorphosed quartz sandstone. Very durable and usually the last rock present when all others have been eroded away.
Marble: Metamorphosed limestone. Used for architecture and building material due to its natural beauty. Susceptible to chemical erosion (acid rain).