Rock Basics…background to understand Earth’s landscapes

1. Rock Basics…background to understand Earth’s landscapes The Wave – Western Australia The Wave – Utah

2. Rock Basics: Background to understand Earth’s landscapes Topic 1. Composition of Continental Crust Topic 2. Introduction to Minerals Topic 3. Basic Rock Types Topic 4. Details on Igneous Rocks Topic 5. Details on Sedimentary Rocks Topic 6. Details on Metamorphic Rocks Topic 7. Trying to think like a geologist

3. Annenberg www.learner.org/resources/series78.html

5. Topic 1. Composition of the Continental Crust • O- Oxygen 47% • Si- Silicon 28% These together = 75% of continental crust • Al- Aluminum 8.1% • Fe- Iron 5.0% • Ca- Calcium 3.6% - nutrient • Na- Sodium 2.8% - nutrient • K - Potassium 2.6% - nutrient • Mg- Magnesium 2.1% - nutrient

6. How much do you consume? 40,000 pounds Earth/year! In a lifetime: • 1050 pounds of lead • 1050 pounds of zinc • 1750 pounds of copper • 4550 pounds of aluminum • 91,000 pounds of iron • 360,500 pounds of coal • 1 million pounds of industrial minerals (calcite, clay, borate)

7. Topic 2. Introduction to Minerals

9. Examples Silicates -- have Si as base, Quartz (Si02) - obvious 75% Feldspars- have Si and Al -- and when add (Ca, K, Na), you get Feldspars Clay minerals that stick to your boot and have layered structures

10. Topic 3. Basic Rock Types IGNEOUS SEDIMENTARY METAMORPHIC

11. Igneous (made by “fire”) - Solidified from molten rock (i.e., magma). Sedimentary - Deposited and buried close to Earth’s surface. Metamorphic (“changed form”) - Transformed from preexisting rocks under high pressure, temperature & fluids.

12. Rocks A rock is a naturally occurring, solid aggregate of minerals.

13. Rock Types Sediments make up 75% surface area Sedimentary rocks are most abundant near Earth’s surface - poor preservation Igneous and Metamorphic rocks make up most of the crustal volume - limited exposure Sediments make up only 5% by volume

14. Topic 4. Details on Igneous Rocks • Minerals crystallize from melt, derived from deep within Earth’s crust or mantle • High temperatures, 700° C & more • Crystal size depends on cooling rate. • Intrusive rocks cool slowly within deep magma chambers: • Coarse, interlocking crystals • Extrusive rocks cool rapidly at (or near) the surface of the earth: • Fine-grained, often “glassy”

15. Igneous Rocks Common in volcanic areas & plate boundaries

19. Least Silicon (Mafic) Diorite Most Silicon (Felsic) Gabbro Diorite Granite

20. Classroom Resources Extrusive Igneous (lava) – Hawaii Basalt Flow a’a’ flow pahoehoe flow

22. Intrusive igneous magma chamber - Pluton

23. Roof pendant (dark metamorphosed sedimentary rock) comprised of remnant “country rock” is draped over the younger intruded Sierra Nevada batholith (light colored granodiorite).

24. Basalt

26. Topic 5. Details on Sedimentary Rocks • Loose particles (sand, silt, marine shells) accumulate on shorelines, basins, rivers, etc., • Clastic Sediments • Minerals precipitate from dissolved chemicals in water • Chemical & Biochemical Sediments • All are the products of Weathering - that breaks up and decays rocks, and Erosion - that transports from source to point of deposition

27. Common along passive margins (and other basins) Weathering & Erosion Transport Basement Rocks Clastic: Sandstone Deposition Chemical: Rock Salt

28. Lithification

29. Conglomerate Shale Sandstone Breccia

30. Large to Small

31. Sedimentary Silicates (esp. Clays) Carbonates Sulfates & Halides (Precipitates)

32. Topic 6. Details on Metamorphic Rocks • High temperatures and pressures at depth cause changes in mineralogy, texture, and composition • Changes take place in Solid State by recrystallization and chemical reactions • Temperatures greater than 250°, less than 700° • Regional Metamorphism - High pressures and temperatures derive from regional collision, deformation and mountain building. • Contact Metamorphism - Locally high temperatures, adjacent to intrusions.

33. Metamorphic Rocks Common at convergent plate boundaries

34. Metamorphic Rocks Fig 4.6 • Not Foliated • Distinct low- pressure minerals • Foliations - Planar fabric defined by • Alignment of platy minerals (micas & clays) • Alternating bands of mineral types • Indicative of high pressures and deformation during formation • Pressure-Temperature-time paths

37. Classroom Resources Showing mineral re-alignment into foliations

38. Metamorphic • Silicates predominate • Due to silicate source rocks • Distinctive mineral types indicative of solid state reactions

39. Typical Rock Types Seen by Geologic Origin Sedimentary Types Metamorphic Igneous Types

40. Topic 7. Trying to think like a geologist Thinking in terms of sequences – Classroom Resources: Animations

41. What came first? Next? Last? Last First Disconformity – a time when deposition temporarily stopped “great unconformity” Showing uplift & then erosion

42. Great Unconformity

43. The Rock Cycle • Melting & Intrusion • Solidification of melt • Mountain Building • Uplift & Exposure • Weathering • Erosion & Transport • Deposition & Burial • Metamorphism • Melting & Intrusion

44. Online Resource Rock Cycle http://serc.carleton.edu/NAGTWorkshops/visualization/collections/rock_cycle.html

45. Geologic Time – Getting a year timeline has been only recently In Classroom Resources Folder, clip about figuring out age of Earth

47. Geologic Time Large blocks of time represented by changes in evolution

48. Classroom Resource Geologic Time as Football Field

49. Toilet Paper Used to Grasp Time Depth http://serc.carleton.edu/quantskills/activities/TPGeoTime.html

50. Review • Continental Crust = O, Si, Al, Fe, & traces • Minerals: specific chemical & crystalline structures • Rocks: combination of minerals • Main rock types: igneous, sedimentary, & metamorphic; felsic = light-colored, mafic = dark-colored • Rocks go through a cycle • Geologic time is VERY long timeframe...