Physical Geography: Landforms of California

1. Physical Geography: Landforms of California

4. Overview • Geologic Time • Movements of the Continents • Earth Materials • Tectonic Forces • Weathering and Erosion Processes • Erosional Agents and Deposition

5. Geologic Time Pretend the age of the earth (4.6+ billion years) is compressed into one calendar year. January 1 - Earth and planets formed Early March - liquid water stands in pools. Late March - earliest life July - oxygen is important part of atmosphere October 25 - multicellular organisms Late November - plants and animals abundant December 15 to 25 - dinosaurs arise and disappear 11:20 pm, December 31 - Humans appear One second before midnight - Automobile invented

6. The Earth’s Interior • General trends: temperature, density • Horizon composition, behavior Distance: 6730 km (3963 miles)

7. Earth Materials • Three major rock types • Igneous • Sedimentary • Metamorphic

8. Igneous Rocks • Igneous (ignus = fire) • Formed from the cooling of molten rock (magma/lava), a process called crystallization. • Slow cooling  larger crystals > dense rock • Rapid cooling  small crystals > lighter rock

9. Two classes of igneous rocks • intrusive: formed inside the Earth • extrusive: formed at Earth’s surface

10. Igneous Intrusive Rocks • Cools slowly (thousands of years) • Visible crystals • Examples - granite - diorite - gabbro

11. Igneous Extrusive Rocks • Cools rapidly - exposed to surface • No visible crystals • Examples - rhyolite - andesite -basalt

12. Typical Igneous Intrusions Know: Batholith and Dike

13. Exposed Batholiths Sierra Nevada, CA

14. Sedimentary Rocks

15. Sedimentary Rocks Relative Abundance by Type Cementing Compaction Formation

16. Limestone (CaCO3) Shale (fine grains) Sandstone (larger grains)

17. Where do Sedimentary Rocks Form? Terrestrial environments (non-marine) • Rivers and floodplains (fluvial environment) • Lakes • Deserts (aeolian environment) • Marine environments • Continental shelf • Continental slope and rise (deep sea fans) • Abyssal plain • Beach and barrier islands

19. Metamorphic Rocks or That’s very Gneiss, but I don’t give a Schist! Schist (narrow foliation) Gneiss (broad foliation)

20. The Unstable Landscape: California Plate Tectonics

21. Crustal Processes • Destruction (subduction) • Creation (volcanism ) • Alteration / deformation (folding and faulting)

22. Introduction • Plate boundaries: main location for Earth’s volcanic and earthquake activity. • Type of plate boundary determines activity. • 3 types • diverging (spreading) • converging (colliding) • transform (sliding past each other)

23. Convergent Plate Boundaries • Action: • collision; destructional or constructional • Activity: • depends on type of convergence • 3 types: ocean-continent, ocean-ocean, cont.-cont.

24. Convergent: Ocean-continent • Action: • collision; destructional (subduction of ocean plate) • Activity: • shallow to deep earthquakes; volcanism (continental) • Features: • ocean trench; volcanic mtns on continental margin

25. Volcanoes: Explosive • Composite cones (stratovolcano) • pointed, steep-sided, tall volcanoes • “Composite”: layers of pyroclastics and lava (mostly felsic) • Explosive and dangerous; found near subduction zones

26. Volcanoes: Explosive Arenal, Costa Rica Mt. Shasta, California Mt. Lassen, California

30. Crustal Deformation:Folding, Faulting, and Earthquakes

31. Introduction • Crustal Processes • Destruction (subduction) • Creation (volcanism - convergent/divergent) • Alteration / deformation (folding and faulting)

32. Crustal Deformation • Outcome / result of “battle”: Stress v. strain (force v. resistance) • Stress: force imposed on the rock (tension, compression and shear) • Strain: how the rock responds to the stress (folding / bending or faulting / breaking) Is the rock brittle or ductile?

33. Figure 12-7

34. Faulting • Definition: fractures where some type of displacement (movement) has occurred along a break in rock. • Three types • normal • reverse/thrust • transform (strike-slip) Carmel Valley Fault, CA

36. Normal Faults • Tensional stress • Earthquake and displacement along fault plane  fault scarp

37. Landforms - Normal Faulting Owens Valley, CA Sierra Nevada, CA Grand Tetons, WY

38. Basin and Range • Horst and graben (“hill” and “grave”) • Death Valley/ Panamint Ranges • Why saline?

39. Landforms: Normal Faulting • Grabens (“Graves”)

40. Basin and Range

41. Transform Plate Boundary • Action: • shear (lateral motion) • no loss/gain of plate material

42. San Andreas fault system • How long is it? About 1000 km • Relative motion of the Pacific Plate? @ 2 inches (5 cm) northwest per year. In 10 million years Los Angeles will be off of San Francisco .

43. San Andreas Fault System - Southern California

44. Transform Plate Boundary • Activity: • shallow to moderate earthquakes • little to no volcanism http://quake.usgs.gov/recenteqs/ Tremblor Range Dragon’s Back Carrizo Plain, CA (view to the east)

46. Transform Plate Boundary • Features: • shallow, linear rift valleys • sag ponds Carrizo Plain, central CA • San Andreas Lake (Crystal Springs Reservoir) • - looking south along fault • - San Francisco water supply • - geology  vegetation

47. Transform Plate Boundary • Features: • offset streams, objects Stream channel offset, Carrizo Plain, central CA 1906 earthquake offset, Point Reyes, CA

48. The Geography of Earthquakes • USA: 1977-1997 earthquake events • USA: every state except ND, FL

49. The Geography of Earthquakes • Globally: primarily at plate boundaries • Intraplate earthquakes do occur! Mag 6.5

50. Earthquakes • Earthquakes are the shaking or vibration of the ground as a result of rocks suddenly breaking along a fault. • Focus (hypocenter) = rupture point • Epicenter = point on surface above focus • Foreshocks • Aftershocks