1. IGNEOUS, SEDIMENTARY, AND METAMORPHIC
EARTH SCIENCE ROCKS
IGNEOUS, SEDIMENTARY,
AND METAMORPHIC

2. WHAT IS A ROCK? A rock is a group of minerals that are bound together.
Rocks are MIXTURES because they have varying percentages of different minerals
Rocks are classified according to how they were formed.

3. THREE GENERAL TYPES OF ROCKS:
Igneous rocks—formed by the cooling and hardening of magma from inside the earth.
Sedimentary rocks—formed by the compaction and cementing of layers of sediments
Metamorphic rocks—formed by the effects of heat and pressure on other rocks

4. ROCK CYCLE Rocks form from other rocks.
The rock cycle is the repeated series of events by which rock gradually and continually changes from one type to another.

5. “WORDY VERSION” OF ROCK CYCLE
Magma (hot, molten rock) beneath the earth’s surface is the source of all rocks.
Once magma reaches the surface (lava), or cools in the interior (as magma) igneous rocks are formed.
Once igneous rocks are weathered and erodedsedimentary rocks are formed.
Sedimentary rocks (and sometimes igneous rocks) are buried and caught in Earth’s movementsmetamorphic rocks are fomed.

6. “Schematic” ROCK CYCLE

7. “VISUAL” ROCK CYCLE

8. MAGMA Is hot, molten rock beneath Earth’s surface
Is called lava once it reaches the surface
Four types:
Felsic
Intermediate
Mafic
Ultramafic

9. FELSIC MAGMA Thick and slow moving Large amounts of silica
Hardens into rocks of light-colored silicate minerals

10. MAFIC MAGMA Hotter, thinner than felsic
Large amounts of iron and magnesium
Forms rocks of darker colors

11. INTERMEDIATE MAGMA
Mix between felsic and mafic

12. Green in color or green tint Varying densities
Ultramafic
Low Si
High Fe and Mg
Green in color or green tint
Varying densities
Kimberlites are rare ultramafic rocks where diamonds have been found in Kimberly, S Africa
Peridotite
Dunite

13. IGNEOUS ROCKS
Although all igneous rocks form from magma, they are not all the same.
The differences are caused by:
Variations in the magma’s composition
Variations in the formation process
Formed from underground magma intrusive
Formed at Earth’s surface extrusive

14. TEXTURE OF IGNEOUS ROCKS
The texture of an igneous rock is caused by the rate of cooling.
Cools rapidly extrusive glassy, fine-grained texture
Cools slowly intrusive coarse texture, crystals formed

15. Igneous Textures
Fine Grained- cools fast, small crystals form (too small to be seen without the use of a microscope)
Basalt
Coarse Grained- cools slowly, large visible crystals (easily seen with the eye, many colors or patterns)
Granite

16. Igneous Textures Glassy: cools too fast for crystals to form.
Pumice
Obsidian
Porphyritic: mixture of fine and coarse grains. Fine grained ground mass with large crystals mixed in.
Andesite

17. Bowen’s Reaction Series
A Canadian scientist, N.L. Bowen, demonstrated that as magma cools, minerals form in predictable patterns.
Each mineral crystallizes at a different temperature.
SEE “Explore” of your Discovery Techbook, Igneous Rocks

19. FAMILIES OF IGNEOUS ROCKS
Are grouped together based solely on mineral composition, so a family can have rocks of all different textures and origins.
Three main families:
Granite Family
Gabbro Family
Diorite Family

20. GRANITE FAMILY Form from felsic magmas
Usually coarse-grained from slow cooling
Usually made of quartz, feldspar, mica, and hornblende
Granite
Obsidian
Pumice
Rhyolite

21. GRANITE

22. OBSIDIAN

23. PUMICE

24. RHYOLITE

25. GABBRO FAMILY Mainly made from mafic magma
Darker in color and denser than granite family
Gabbro
Basalt
Scoria

26. GABBRO

27. BASALT

28. SCORIA

29. DIORITE FAMILY
From intermediate magma (characteristics of felsic and mafic)
Color is darker than granites and lighter than gabbros (dark greys and greens)
Diorite
andesite

30. DIORITE

31. ANDESITE

32. IGNEOUS INTRUSIONS
Are rock masses that form when magma cools inside Earth’s interior
Forces within the earth push magma up into the bedrock
Igneous intrusions are also called plutons

33. TYPES OF IGNEOUS INTRUSIONS
Dikes—sheet of igneous rock cuts across rock layers vertically or at a steep angle
Sills—sheet of igneous rock that lies parallel to the layers it intrudes
Laccoliths—from stiff magma that does not flow easily—bulges upward to form domed masses
Batholiths—form core of mountain ranges (largest of all intrusions)

34. SEDIMENTARY ROCKS
While most of the earth’s crust is made of igneous rock, most of the earth’s surface is made of sedimentary rock
Formed from the compaction and cementation of layers of sediments

35. FAMILIES OF SEDIMENTARY ROCKS
Are grouped according to their formation process
Three general groups in text:
Clastic
Chemical
Organic

36. CLASTIC ROCKS Are formed from the fragments of other rocks
Conglomerates—the coarsest clastic rocks
Sandstones—made of quartz and sand
Shales—made of silt and clay

37. CHEMICAL ROCKS Made when minerals precipitate out of a solution
Rock salt
Rock gypsum
Some limestones

38. ORGANIC ROCKS Form from sediments of plant or animal remains Limestone
Coal

39. LIMESTONE

40. COAL

41. FEATURES OF SEDIMENTARY ROCKS
Stratification
Fossils
Ripple marks
Mud Cracks
Nodules
Concretions
geodes

42. STRATIFICATION The arrangement of visible layers
Most apparent characteristic of sedimentary rocks
Line between layers is called bedding plane
Usually horizontal, but cross-bedding can occur

43. FOSSILS
The remains, impression, or any other evidence of a plant or animal preserved in rock

44. RIPPLE MARKS
Sand patterns formed by the action of winds, streams, waves, or currents

45. MUD CRACKS
Occurs where a muddy road or puddle of water has dried out after the rain
Modern Ancient

46. NODULES
Hard lumps of silica in limestone and chalk

47. CONCRETIONS
Round, solid masses of calcium carbonate in layers of shale

48. GEODES
Spheres of rocks filled with crystals that occur in limestones

49. METAMORPHIC ROCKS
Formed by the effect of heat and pressure on other rocks
Formed from pre-existing rocks called parent rocks
Usually resemble their parent rocks

50. METAMORPHISM
Process by which a rock’s structure is changed by heat, pressure, and moisture
Two Basic Types:
Regional
Local

51. REGIONAL METAMORPHISM
Occurs in large areas
Forms most of the metamorphic rock of Earth’s crust
Can occur during mountain-building process

52. LOCAL METAMORPHISM Occurs in smaller, distinct areas Two Types:
Contact hot magma moves into rock, heating and changing it (can even change mineral compostion)
Deformational occurs at lower temperatures and is more due to pressure (composition does not change but deforms shape and texture)

53. CLASSIFICATION OF METAMORPHIC ROCKS
Based on a variety of properties:
Parent rock
Mineral content
Texture
Foliation—tendency to form bands of minerals or split along parallel layers

54. CLASSIFICATION OF METAMORPHIC ROCKS
Metamorphic Rocks are also classified by their “grade” or degree of metamorphism:

55. Even the minerals in a rock can change with metamorphism (but not always!)

56. EXAMPLES OF METAMORPHIC ROCK
Quartzite a metamorphosed sandstone
Marble a metamorphosed limestone
Slate, phyllite, schist metamorphosed shales
Gneiss—most highly metamorphosed from a variety of parent rocks

57. QUARTZITE

58. MARBLE

59. SLATE

60. SCHIST

61. GNEISS