1. UNIT 3 ROCKS AND THE ROCK CYCLE A Rock is composed of one or more minerals that are naturally occurring. There are three rock types a.Igneous-formed by cooling magma. b.Sedimentary-formed by the breakdown of other rocks. c.Metamorphic-formed when preexisting rocks are heated under pressure.

2. Some rocks are composed entirely of one mineral ex. Limestone (mineral) calcite. Most rocks have more than one kind of mineral ex. Granite Some rocks contain non-mineral matter. Ex coal organic debris, and obsidian volcanic rock- not crystalline.

3. rock minerals mineral

4. Example: Granite & its constituent minerals:  Quartz  Amphibole (hornblende)  Feldspar

5. A.THE ROCK CYCLE 1.Igneous- formed by the crystallization of molten rock material called magma. 2.Sedimentary-formed from pre-existing rocks by weathering-chemical and physical breakup, erosion, and transport. 3.Metamorphic-formed by textural and compositional changes that occur when pre- existing rocks are buried and subjected to increased temperatures and pressures.

6. The rock cycle connects the three rock groups to each other by processes. The rock cycle is embedded within the hydrological and plate cycles.

7. 7 MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY METAMORPHIC Uplift Burial Increased P&T Melting Crystallization Weathering Erosion Transport Deposition

9. B. Igneous Rocks Molten rock inside the Earth is called Magma. Magma is buoyant, rises to the surface and sometimes breaks through as volcanic eruptions. When magma reaches the surface it is called lava. An igneous rock is formed when magma or lava cools and solidified.

11. Igneous rocks make up the bulk of the Earth’s crust. Earth’s mantle is composed entirely of igneous rock. Igneous rocks are important economically as building stones and as host rocks for a variety of mineral (ore) deposits.

12. Volcanic activity is a geological hazard, igneous rock can tell us both the nature of past volcanic eruptions and the potential for future eruption hazards. Igneous rocks that form by magma at the surface are called volcanic or extrusive. Fragmented materials are called pyroclastic and consist of ash & cinders.

13. Crystal Size Slow cooling Cooling Rate larger crystals Fast coolingsmall or no crystals In igneous rocks, texture is controlled by the cooling rate of the magma.

15. Plutonic Igneous Rocks Igneous rocks that form deep below the surface are called plutonic (intrusive) plutonic (intrusive) igneous rocks. To see them, they must be uplifted to surface and the overlying rock eroded away.

16. As a magma cools, atoms arrange themselves into orderly crystalline structures called minerals. This process is called: Crystallization Crystallization

20. Plutonic igneous rocks cool slowly at depth and are therefore coarser grained! Microscopic views of plutonic igneous rocks

21. Subsurface intrusion called a dike

22. All rocks are classified according to their texture and mineral composition. Texture involves the size, shape, and arrangement of the minerals making up a rock.

23. Types of Igneous Textures Fine-grainedCoarse-grained Porphyritic Glassy

24. C. Types of igneous textures 1. Fine-grained-fast cooling magma/lava forms at or near surface sometimes gas holes present, hard to see individual crystals. 2. Coarse-grained-forms deep below the surface slowly cooling. The crystals are coarse and intergrown. 3. Porphyritic- magma cooled slowly for a while then erupted. Minerals crystallized at different temperatures and rates over a period of time,

25. 4. Glassy-rapid cooling at the surface. Cannot form orderly crystalline structures.

27. Fig. 6.12 W. W. Norton

28. Basalt Gabbro Zooming in:

29. Andesite Diorite Zooming in

30. Obsidian Pumice V olcanic Glass V olcanic “Froth”

32. Fig. 6.20a W. W. Norton Columbia River basalts Basalt eruptions on land produce flows that travel great distances.

33. Fig. 6.21a W. W. Norton

34. Fig. 6.21b Stephen Marshak

35. Fig. 6.02 W. W. Norton

36. D. Explosive Volcanic Eruptions. Violently explosive volcanic eruptions produce rock fragments of all sizes, finely-fragmented ash, and molten bombs. They accumulate to form pyroclastic volcanic rocks. Rock types from these volcano’s include: a. Tuff-composed of ash, finely fragmented volcanic rock. b. Scoria-red or black, frothy lave, denser then pumice.

37. c. Volcanic Breccia-coarse, angular rock fragments, usually in a matrix of fine to coarse ash.

39. Fig. 6.08a W. W. Norton

40. p.140-141d Original artwork by Gary Hincks Types of Igneous Plutons Sills Dikes Laccolith Volcanic Pipe Batholith Dikes Volcano

41. Fig. 6.08b Stephen Marshak

43. Fig. 6.10 W. W. Norton

44. Fig. 6.11a Stephen Marshak

45. Fig. 6.11de Paul Hoffmann

46. Fig. 6.18 W. W. Norton