1. The Rock Cycle

2. Types of Rocks There are three main types of rocks.
Igneous Rocks
Sedimentary Rocks
Metamorphic Rocks
We will learn more about each type in the following lectures.

3. The Rock Cycle
Interactions among water, air, land, and living things on Earth can cause rocks to change from one type to another.
The processes that cause rocks to change make up the rock cycle.
There are alternate paths that can be taken in the rock cycle for other types of rocks to form.

4. The Rock Cycle: Igneous Rock Formation
When magma cools and hardens beneath the surface or as a result of a volcanic eruption, igneous rocks form.
Note that when magma reaches the Earth’s surface, it is called lava.
Magma: molten material beneath the Earth’s surface.
Lava: molten material on the Earth’s surface.

5. The Rock Cycle: Igneous Rocks  Sedimentary Rocks
When an igneous rock is brought to the Earth’s surface, it will undergo weathering.
Weathering: The process in which rocks are physically and chemically broken down by water, air, and living things.
The pieces of material that are weathered are known as sediments.
Sediments: Weathered pieces of Earth material.
Over time, these pieces of sediments are compacted and cemented together to form Sedimentary Rocks.

6. The Rock Cycle: Sedimentary Rocks  Metamorphic Rocks
Over time, sedimentary rocks may become buried deep within Earth.
At this point, the rocks can be subject to increases in temperature and/or pressure.
Under these conditions, sedimentary rocks will change into metamorphic rocks.

7. The Rock Cycle: Metamorphic Rocks  Magma
If metamorphic rocks undergo additional pressure changes or temperature changes, they may melt to form magma.
Once this happens, the magma can once again crystallize to form igneous rocks again.

8. The Rock Cycle: Alternate Paths
As mentioned earlier, rocks don’t always follow the true path of the rock cycle.
Processes that are driven by heat can cause igneous rocks or even metamorphic rocks to form.
Process that are driven by weathering allow for material to move and can produce sedimentary rocks.

9. https://www. khanacademy
ea/v/rock-cycle

10. Igneous Rocks

11. Objective-SWBAT:
Identify igneous rocks by where they form and crystal size.

12. Igneous Rocks
Form from the cooling of magma (material below the surface of the earth) or lava (material above or on the surface of the earth)

13. 2 Types of Igneous Rocks
Intrusive (plutonic): forms from the cooling of magma beneath the surface of the earth.
Ex. Granite
Extrusive (volcanic): forms from the cooling of lava on the surface of the earth.
Ex. Obsidian

14. Classification
Igneous rocks are classified according to composition and texture.

15. Igneous rocks are divided into 3 families (by composition)
Granite family >65% Silica
Felsic
Light-colored
Formed from magma/lava high in silica
Ex. Orthoclase feldspar, quartz (SiO2)
Quartz
Orthoclase Feldspar

16. Families continued… Diorite family (Andesitic) 55-65% Silica
Neither felsic nor mafic
Intermediate colored
Ex. Mostly plagioclase feldspar, horneblende, augite and biotite mica
Plagioclase Feldspar
Horneblende
Augite
Biotite Mica

17. Families Continued Basalt family 45-55% Silica Mafic Dark colored
Formed from magma/lava rich in iron (Fe)
Hotter, thinner and more fluid liquid
Ex. Basalt

18. Families Continued… Ultramafic <45% Silica Mostly Fe and Mg
Ex. Peridotite

19. Classified by texture
Determined by how fast or slow the magma/lava cools
Intrusive igneous rocks cool slowly = coarse grained (large mineral grains)
Extrusive igneous rocks cool quickly = fine grained (small/no mineral grains)
Intrusive
(Diorite)
Extrusive
(Pumice)

20. Exceptions
Some intrusive igneous rocks cool slowly at first and then more rapidly. This produces porphyry (mixture of small and large crystals)…Intermediate/fragmental…Ex. Tuff
Extremely rapid cooling can give extrusive igneous rocks a “glassy” (Ex. Obsidian) or “frothy” (Ex. Scoria or Pumice) look. These do not have crystals.
Tuff
Obsidian
Scoria

22. True or False
Intrusive igneous rocks form from the cooling of lava on the surface of the earth.
False
Granite, Basalt and Diorite are the 3 families of igneous rocks.
True
Felsic rocks are dark colored and mafic rocks are light colored.

23. Made from an accumulation of various types of sediments
Sedimentary Rocks
Made from an accumulation of various types of sediments

24. Objective-SWBAT:
Identify sedimentary rock based on methods of formation, grain size, and composition.

25. What is sediment?
Fragments that result from the breaking (weathering) of rocks, minerals, and organic matter.
Ex. Gravel, clay, silt, pebbles, sand, mud, shells, dirt

26. Most sedimentary rock form under water.
Ex. Limestone, halite
Limestone is a rock that is composed primarily of calcium carbonate. It can form organically from the accumulation of shell, coral, algal and fecal debris. It can also form chemically from the precipitation of calcium carbonate from lake or ocean water. Limestone is used in many ways. Some of the most common are: production of cement, crushed stone and acid neutralization
Rock Salt is a chemical sedimentary rock that forms from the evaporation of ocean or saline lake waters. It is also known by the mineral name "halite". It is rarely found at Earth's surface, except in areas of very arid climate. It is often mined for use in the chemical industry or for use as a winter highway treatment. Some halite is processed for use as a seasoning for food.

27. Sedimentary rock forms from these processes:
W – weathering
E – erosion
D – deposition
C – compaction
C - cementation

28. Sedimentary rock forms from these processes:
Compaction: sediments are pushed together and as a result, water and air are squeezed out.
Cementation: water passes through the sediments and dissolved minerals left behind act as a cement to hold the sediments together.

29. Other processes that form Sedimentary Rocks:
Precipitation: minerals clump together and fall out of solution
Evaporation: Water evaporates and leaves dissolved minerals behind.

30. There are three types of sedimentary rocks.
Clastic:
Formed from fragments of other rocks which have been weathered and eroded
Classified by the size of the sediments (coarse- pebbles or larger, medium-sand sized, or fine-clay or silt sized)
Ex. Sandstone (sand), shale (silt or clay), conglomerate (round pebbles), and breccia (angular pieces)

31. Breccia Conglomerate How are breccia and conglomerate different?
Breccia is a clastic sedimentary rock that is composed of large (over two millimeter diameter) angular fragments
Conglomerate is a clastic sedimentary rock that contains large (greater then two millimeters in diameter) rounded particles.

32. Shale
Sandstone
Shale is a clastic sedimentary rock that is made up of clay-size (less then 1/256 millimeter in diameter) weathering debris. It typically breaks into thin flat pieces
Sandstone is a clastic sedimentary rock made up mainly of sand-size (1/16 to 2 millimeter diameter) weathering debris. Environments where large amounts of sand can accumulate include beaches, deserts, flood plains and deltas.

33. Chemical: Formed from minerals that were once dissolved in water.
Either the minerals “settle” out of the water (precipitates) or the water evaporates leaving the minerals behind (evaporites)
Classified by their mineral composition
Ex. Chemical Limestone (CaCO3), gypsum (CaSO4), halite (NaCl)

35. Organic: Formed from the remains or traces of animals and/or plants
Ex. Coal (plants), chalk (animal skeletons), organic limestone (shells-CaCO3)
Coccolithophores are the most important group of chalk forming plankton. Each miniscule individual has a spherical skeleton called a cocosphere, formed from a number of calcareous discs called coccoliths. After death, most coccospheres and coccoliths collapse into their constituent parts. Most chalks formed during the Cretaceous period, between 100 and 60 million years ago, and chalks of this age can be found around the world.

37. Features of Sedimentary Rocks
Stratification: (aka. Layering) occurs when there is a change in the kind of sediment deposited.
Ex. Grand Canyon

38. The truth is that no one knows for sure though there are some pretty good guesses. The chances are that a number of processes combined to create the views that you see in todays Grand Canyon. The most powerful force to have an impact on the Grand Canyon is erosion, primarily by water (and ice) and second by wind. Other forces that contributed to the Canyon's formation are the course of the Colorado Riveritself, vulcanism, continental drift and slight variations in the earths orbit which in turn causes variations in seasons and climate.

39. Features Continued…
Ripple marks: formed from the action of wind or water on sand (seen in sandstone)
Ripple marks in sedimentary rock were emplaced in sediments by near shore wave action, covered by additional sediments, and eventually lithified into a solid rock which becomes exposed by weathering and erosion of overlying material over large expanses of time. 

41. Fossils: remains or traces of plants and/or animals

42. Metamorphic rocks

43. Objective-SWBAT:
Identify metamorphic rocks based upon composition and parent rocks.

44. Metamorphic rocks
Rock formed from other rocks (igneous, sedimentary, or metamorphic) as a result of intense heat (from magma) and pressure (plate tectonics).
Most metamorphic rock forms below the surface of the earth at an increased temperature or pressure.

45. Metamorphic rock can form in 2 ways:
1) contact metamorphism: occurs when hot magma pushes through existing rock and changes the structure and composition of the surrounding rock. The original minerals may form larger crystals.

46. 2) Regional Metamorphism: occurs when tectonic plates push against each other causing heat and pressure that chemically changes the minerals in the rock (most metamorphic is formed this way).

47. Agents of Metamorphism
Heat:
Provides the energy needed to drive chemical reactions.
Comes from two sources
Magma and the temperature change with depth.

48. Agents of Metamorphism Continued…
Pressure (stress):
Increases with depth like heat.
Pressure is applied in all directions.
Increases in pressure and temperature cause rock to flow rather than fracture.

49. Agents of Metamorphism continued…
Hydrothermal solutions:
When hot, water-based solutions escape from a mass of magma.
Aid in recrystallization by dissolving original minerals and depositing new ones.
Can change the rocks overall composition.

51. Classification
Metamorphic rocks are classified according to their structure.

52. Foliated Metamorphic rock
Pressure flattens the mineral crystals and pushes them into parallel bands.
Minerals with different densities separate into different bands
EX. schist, and gneiss

53. Schist
Gneiss

54. Nonfoliated Metamorphic Rock
No visible parallel bands
EX. Quartzite, marble
Marble
Quartzite
Marble is a non-foliated metamorphic rock that is produced from the metamorphism of limestone. It is composed primarily of calcium carbonate. 

55. Parent rock: the rock From which a metamorphic rock is formed
Limestone--> Marble (u)
Shale--> Slate (f)
Granite --> gneiss (f)
Slate --> schist (f)
Quartz --> Quartzite (u)
Sandstone --> quartzite (u)
Talc --> soapstone (u)
Gneiss --> Schist (f)