1. MINERAL MIXTURES
CHAPTER 2

2. Section 1 The Rock Cycle
A rock is defined as a naturally occurring solid mixture of one or more minerals and organic matter
The continual process by which new rock forms from old rock material is called the rock cycle

3. The value of Rock Early humans used as tools
Used for centuries to make buildings
Granite, limestone, marble, sandstone, slate, etc.
Modern buildings use concrete and plaster where rock is an important ingredient

4. Processes that Shape the Earth
Weathering, Erosion, and Deposition
The process in which water, wind, ice, and heat break down rock is called weathering.
Weathering breaks rocks into fragments that become the sediment that are used to make sedimentary rocks

5. The process by which sediment is removed from its source is called erosion
Water, wind, ice and gravity can erode and move sediments and cause them to collect

6. The process in which sediment moved by erosion is dropped and comes to rest is called deposition.
Sediment is deposited in bodies of water and other low-lying areas and can be pressed and cemented together by minerals dissolved in water to form sedimentary rock.

7. Heat and Pressure
Sedimentary rock made of sediment can also form when buried sediment is squeezed by the weight of overlying layers of sediment
If the temperature and pressure are high enough at the bottom, the rock can change into metamorphic rock.
Sometimes the rock gets hot enough to melt, creating magma that eventually cools to form igneous rock

8. How the Cycle Continues
Uplift is movement within the Earth that causes rocks inside the Earth to be moved to the Earth’s surface.

9. Buried rock is exposed at the Earth’s surface by a combination of uplift and erosion
When uplifted rock reaches the Earth’s surface, weathering, erosion, and deposition begin.

10. Illustrating the rock cycle

11. Round and Round it Goes
Each type of rock can change into one of the 3 types of rock
This cycle, in which rock is changed by geological processes into different types of rock, is known as the rock cycle
The location of rock determines which natural forces will have the biggest impact on the process of change

12. Rock Classification: Each rock type can be further divided depending on how it was formed.
Composition: The minerals a rock contains determine the composition of that rock
Texture: The size, shape, and positions of the grains that make up a rock determine a rock’s texture
The texture of a rock can provide clues as to how and where the rock is formed

13. Section 2: Igneous Rock

14. Igneous rock forms when hot, liquid rock or magma, cools and solidifies
The type of igneous rock that forms depends on the composition of the magma and the amount of time it takes the magma to cool.

15. Origins of igneous Rock
Igneous rocks begin as magma.
Magma forms in 3 ways:
When rock is heated
When pressure is released
When rock changes composition

16. When magma cools enough, it solidifies to form igneous rock
Liquid magma contains many melted minerals and these minerals have different melting points so magma will freeze or become solid before other minerals do.

17. Composition and Texture of igneous Rock
Felsic Rocks – light colored rocks rich in elements such as aluminum, potassium, silicon, and sodium
Granite
Rhyolite

18. Mafic Rocks – Dark-colored rocks rich in calcium, iron, and magnesium, and poor in silicon
Basalt

19. The longer it takes for the magma to cool, the more time the mineral crystals have to grow and therefore the larger the crystals are and the coarser the texture of the resulting igneous rock is.
The less time it takes for the magma to cool, the less time the crystals have to grow so the rock being formed will be fine grained.

20. Igneous Rock formation
Formations are located above and below the Earth’s surface

21. Intrusive Igneous Rock – when magma intrudes, or pushes, into surrounding rock below Earth’s surface and cools
Usually coarse because it is insulated and cools slowly
The minerals that form are large visible crystals

22. Plutons are large, irregular shaped intrusive bodies

23. Batholiths are the largest igneous intrusions

24. Stocks are intrusive bodies that are exposed over smaller areas than batholiths

25. Dikes are sheet-like intrusions that cut across previous rock units

26. Sills are sheet-like intrusions that are oriented parallel to previous rock units

27. Extrusive igneous Rock – igneous rock that forms from the magma that erupts, or extrudes, onto the Earth’s surface
Common around volcanoes
Cools quickly on the surface
Contains very small or no crystals
Sometimes lava flows from volcanoes
Obsidian

28. Sometimes lava flows from cracks in the Earth’s surface called fissures
Fissures in the ocean floor causes the creation of new ocean floor
Large amounts of lava from fissures on land can cover a large area and form a plain called a lava plateau
Pre-existing landforms are often buried by these lava flows.

29. Land Fissure

30. Ocean Fissure

31. The Giant’s Causeway is an area of 40,000 joined basalt columns which is a result of volcanic eruptions in the Paleocene. It is located in County Antrim on the northeast coast of Northern Ireland, near the city of Bushmills.

32. Section 3: Sedimentary Rock

33. Through the process of erosion sediments are moved from one place to another, eventually deposited in layers; older layers become compacted; dissolved minerals separate from water that passes through the sediment to form a natural cement that binds the rock and minerals together into sedimentary rock.
Sedimentary rock forms at or near the Earth’s surface, without heat or pressure that is involved in metamorphic or igneous rocks
The most noticeable feature of these rocks are the layers, or strata.

34. Composition of Sedimentary Rock
Sedimentary rock is classified by the way it forms

35. Clastic sedimentary rock forms when rock or mineral fragments (clasts) are cemented together
Can be coarse, medium or fine grained

36. Sandstone – Fine grained
Conglomerate – Coarse grained
Shale – Fine grained

37. Chemical Sedimentary rock forms when minerals crystallize out of a solution (like sea water) to become rock
Example is Halite which forms when sodium ions and chlorine ions in shallow bodies of water become so concentrated that halite crystallizes from solution
Gypsum
Halite

38. Organic Sedimentary Rock forms from the remains of once-living plants and animals
Most Limestone forms from the fossils of ocean animals, such as coral or mollusks
Coal is another of this type
Coal
Calcite

39. Sedimentary Rock Structures
Stratification is the process in which sedimentary rocks are arranged in layers
Strata differ from each other depending on the kind, size, and color of the sediment

40. Can record the motion of wind and water waves on lakes, oceans, rivers, and sand dunes in features called ripple marks
Structures called mud cracks form when fine grained sediments at the bottom of a shallow body of water are exposed to the air and dry out

41. Section 4: Metamorphic Rocks
Metamorphic rocks are rocks in which the structure, texture, or composition of the rock have changed, or gone through metamorphism.

42. Origins of Metamorphic Rock
Form at 50 to 1,000 ⁰C, but some form at temperatures that are higher!
It is the depth and pressure that the rock forms that allows it to heat up to this temperature and still remain a solid.

43. Two Types of Metamorphism:
Contact metamorphism
When rock is heated by nearby magma
Some minerals in the surrounding rock are changed into other minerals by this increase in temperature
Contact metamorphism occurs near igneous intrusions

45. Regional Metamorphism
When pressure builds up in rock that is buried deep below other rock formations or when large pieces of the Earth’s crust collide with each other, regional metamorphism occurs
Occurs over thousands of cubic kilometers deep within Earth’s crust
Are found beneath most continental rock formations

46. Composition of Metamorphic Rock
Index Minerals are certain minerals that only form at certain temperatures and pressures so they are used to estimate the temperature, depth, and pressure at which a rock undergoes metamorphism.
They include: biotite mica, chlorite, garnet, kyanite, muscovite mica, sillimanite, and staurolite

47. 2 Textures of metamorphic Rock:
Foliated
Mineral grains are arranged in plains or bands
Usually contains aligned grains of flat minerals such as mica or chlorite

48. Nonfoliated The mineral grains are not arranged in planes or bands
Commonly only made of one or only a few minerals
During metamorphism, the crystals of these minerals may change in size or the minerals may change in composition in a process called recrystallization

49. Metamorphic Rock Structures
Deformation is a change in the shape of a rock caused by a force placed on it. (these forces may cause a rock to be squeezed or stretched)
Folds, or bends are structures that indicate that a rock has been deformed.