14-1 What Are the Earth s Major Geological Processes and Hazards?

Transcription

1

2 14-1 What Are the Earth s Major Geological Processes and Hazards? Concept 14-1A Gigantic plates in the earth s crust move very slowly atop the planet s mantle, and wind and water move the matter from place to place across the earth s surface. Concept 14-1B Natural geological hazards such as earthquakes, tsunamis, volcanoes, and landslides can cause considerable damage.

3 3 rd Planet from sun Formed ~4.6 billion years ago Shape = oblate sphere Caused by Earth s rotation Difference between tallest mountain and deepest ocean trench is ~20 km 40,007 km around 40,074 km around

4 3 major concentric zones of earth s interior Crust (Continental and Oceanic-71%) Mantle Core Structural zones of earth s interior Lithosphere Asthenosphere Mesosphere Outer Core Inner core

5 Earth s Interior

6 Major Features of the Earth s Crust and Upper Mantle

7 Plate Tectonics

8 Alfred Wegener s Hypothesis Continental Drift: Hypothesis that the continents once formed part of a single landmass called a supercontinent Began breaking up ~250 million years ago Continents drifted to present location

9 Evidence of Continental Drift Fossil Evidence Fossils found of same species in areas where continents were once connected Evidence from Rock Formations Ages and types of coastal region rocks matched closely Climatic Evidence Glacier deposits where climates are warm

10 Mid-Ocean Ridges Mid-Atlantic Ridge mapped out in 1947 Mid-ocean ridges: undersea mountain ranges through the center of which run steep, narrow valleys.

11 Ridge Facts The sediment covering the sea floor is thinner closer to a ridge Younger sediment closer to a ridge Rocks on land ~3.8 billion years Rocks on sea floor < 175 million years old Oceanic Crust Magma

12 Sea-Floor Spreading Hess proposed a rift (crack at center of ridge) that magma flowed from, ocean floor spreads, magma cools forming rock and replacing gap in ocean floor Dietz defined this process Sea-floor Spreading

13 Paleomagnetism Study of the magnetic properties of rocks Magnetic Reversals Normal Polarity= rocks magnetic field points north (classified together in same time period) Reverse Polarity= rocks magnetic field points south (classified together in same time period) Magnetic Symmetry Stripped magnetic pattern same on each side of the ridge Magnetic patterns help date ocean floor and support seafloor spreading

14 Plate tectonics is the theory that explains why and how continents move and is the study of the formation of features in Earth s crust

15 How Continents Move Lithosphere is divided into tectonic plates, which can also include continental crust, oceanic crust, or both Asthenosphere is under great pressure, therefore flows (moves) slowly allowing the tectonic plates to move above it

16 Tectonic Plates About 7-8 Major Plates (+7-8 more minor plates) Primarily identified using earthquake data Frequent earthquakes is evidence of a boundary Volcanoes are also an identifier when they form from magma generated during plate motion

17 The Earth s Major Tectonic Plates

18 Types of Plate Boundaries

19 The San Andreas Fault as It Crosses Part of the Carrizo Plain in California, U.S.

20 Causes of Plate Motion Mantle Convection

21 Ridge Push The asthenosphere exerting force on the plate pushing the plate away from the ridge Sinking lithosphere Resulting plate motion Moving asthenosphere Slab Pull The force exerted by the sinking plate Direction of plate motion Sinking due to density Resulting plate motion

22 Rifting and Continental Reduction Rifting: the process by which a continent breaks apart Rifts form because heat builds up under the insulating continent, the lithosphere becomes thinner (weaker), the continent breaks apart at the weakness

23 Terranes and Continental Growth Terrane: A piece of lithosphere that has a unique geologic history that differs from the histories of the surrounding lithosphere 3 Characteristics: 1. Rocks and Fossils differ between terranes 2. Major faults at terrane boundaries 3. Magnetic properties differ between terranes

24 Accretion The process in which a terrane becomes part of a continent Occurs at Convergent Boundaries books/earth_science/terc/ content/visualizations/es0 808/es0808page01.cfm?c hapter_no=visualization

25 Effects of Continental Change Changes in Climate Large continent mass was located near the South Pole so was covered by ice When continents moved toward equator the ice melted Changes in Life Rifts and Mountains separate species Species evolve differently when separated and new species may emerge

26 Supercontinent Cycle

27 Some Parts of the Earth s Surface Build Up and Some Wear Down Internal geologic processes - Generally build up the earth s surface External geologic processes Weathering Physical, Chemical, and Biological Erosion Wind Flowing water Human activities Glaciers

28 Weathering: Biological, Chemical, and Physical

29 *SEE WEATHERING AND EROSION POWERPOINT!

30 Volcanoes Release Molten Rock Volcano from the Earth s Interior Fissure: Central vent or long crack Magma: Partially molten asthenosphere Lava: Magma that reaches the earth s surface Benefits of volcanic activity Scenery Fertile soil produced by weathering of lava

31 May 18, 1980 Eruption of Mount St. Helens Elevation of summit: 9,677 feet before; 8,363 feet after; Magnitude 5.1 earthquake at 8:32 a.m. Fatalities Human: 57 Wildlife: Countless non-burrowing wildlife in blast area, including about 7,000 big game animals; about 12 million salmon fingerlings in hatcheries

32 Eruption was Forecasted! 1991 Eruption of Mount Pinatubo, Philippines Resulted in the saving of at least 5,000 lives and at least $250 million in property However, a few jets flying far to the west of the Philippines encountered ash and sustained about $100 million in damage

33 Creation of a Volcano

34 Earthquakes Are Geological Rock-and-Roll Events Earthquake Seismic waves: form of energy vibrations Focus: location where earthquake begins BELOW the surface Epicenter: location ABOVE the surface over focus Magnitude: measure of ground motion Amplitude: size of the seismic wave

35 Richter Scale Developed in 1935 by Charles F. Richter California Institute of Technology Magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. Richter scale Insignificant: <4.0 Minor: Damaging: Destructive: Major: Great: >8.0

36 Earthquakes Are Geological Rock-and-Roll Events Foreshocks: occurs from seconds to weeks BEFORE the main shock Aftershocks: occurs months after main shock, but will decrease in frequency over time

37 Major Features and Effects of an Earthquake

38 Areas of Greatest Earthquake Risk in the United States

39 Areas of Greatest Earthquake Risk in the World

40 1995, Kobe (Japan) The 1995 Great Hanshin Earthquake (M=6.9), commonly referred to as the Kobe earthquake, was one of the most devastating earthquakes ever to hit Japan. More than 5,500 were killed and over 26,000 injured. The economic loss has been estimated at about $US 200 billion.

41 San Francisco earthquake The San Francisco earthquake in 1989 killed nine people and injured hundreds. The earthquake was measured to be a 6.9 Which caused collapsed bridges and freeways, fires, shattered buildings, gaping cracks in roads and land slides

42 1989 earthquake in san Francisco caused a lot of damage to the city

43 Earthquakes on the Ocean Floor Can Cause Huge Waves Called Tsunamis Tsunami (tidal wave): series of large waves generated when ocean floor suddenly rises or drops Detection of tsunamis: ocean buoys, pressure recorder (data relayed to weather buoy)

44 December 2004: Indian Ocean tsunami Magnitude of 9.15 Waves height: 31 meters (100 feet) 228,000 people died Role of coral reefs and mangrove forests in reducing death toll Sri Lanka-illegal coral mining and reef damage were factors in causing the greatest damage here

45 Formation of a Tsunami and Map of Affected Area of Dec 2004 Tsunami

46 Shore near Gleebruk in Indonesia before and after the Tsunami on June 23, 2004

47 Gravity and Earthquakes Can Mass wasting Cause Landslides Slow movement Fast movement Rockslides Avalanches Mudslides Effect of human activities on such geological events Forest clearing, road building, crop growing

48 California PCH and Malibu

49 How Are the Earth s Rocks Recycled? Concept 14-2 The three major types of rocks found in the earth s crust sedimentary, igneous, and metamorphic are recycled very slowly by the process of erosion, melting, and metamorphism.

50 Three Major Types of Rocks Earth s crust Composed of minerals and rocks Three broad classes of rocks, based on formation 1. Sedimentary formed by the lithification of weathered rock debris that has been physically transported and deposited Sandstone Shale Dolomite Limestone

51 Three Major Types of Rocks 2. Igneous: formed by the cooling and solidification of molten magma Granite Lava rock 3. Metamorphic: alteration of existing rocks by either excessive heat and pressure, or through the chemical action of fluids. Anthracite Slate Marble

52 Natural Capital: The Rock Cycle Is the Slowest of the Earth s Cyclic Processes

53 4 Characteristics of Minerals 1. It is INORGANIC 2. It OCCURS NATURALLY 3. It is a CRYSTALLINE SOLID 4. It has CONSISTENT CHEMICAL COMPOSTION

54 Silicate Minerals Minerals that contain a combination of silicon and oxygen Make up 96% of Earth s crust Feldspars are the most common silicates

55 Silicate Minerals Potassium Feldspar Chemical Composition Color Cleavage Hardness Specific Gravity 2.6 Luster Streak KalSi308 Potassium Aluminum Silicate Typically off-white or shades of red, orange and brown, occasionally green. One perfect cleavage and one good cleavage that meet at nearly 90 6 (harder than glass) Crystals are vitreous (glass-like) to porcelaneous (porcelainlike) white

56 Nonsilicate Minerals Do not contain silicone-oxygen compounds ~ 4% of Earth s Crust 1. Carbonates 2. Halides 3. Native elements 4. Oxides 5. Sulfates 6. Sulfides

57 Nonsilicate Minerals Pyrite AKA Fools Gold

58 Crystalline Structure of silicates

59 Crystalline Structure of nonsilicates Examples include cubes, hexagonal prisms, and irregular masses

60 Color Streak Luster Identifying using Physical Cleavage and Fracture Hardness Crystal Shape Density Properties

61 There Are Several Ways to Remove Mineral Deposits Surface mining Shallow deposits removed Subsurface mining Deep deposits removed Type of surface mining used depends on Resource Local topography

62 There Are Several Ways to Remove Mineral Deposits Types of surface mining Open-pit mining: digging holes to remove ores (e.g. iron, copper, gold) and sand, gravel, or stone Strip mining: extract minerals on surface in large horizontal beds Contour mining: cutting terraces into side of hill or mountain Mountaintop removal: remove entire top of mountain

63 Natural Capital Degradation: Open- Pit Mine in Western Australia

64 Natural Capital Degradation: Contour Strip Mining Used in Hilly or Mountainous Region

65 Natural Capital Degradation: Mountaintop Coal Mining in West Virginia, U.S.

66 Mining Has Harmful Environmental Effects Scarring and disruption of the land surface E.g., spoils banks (a series of hills left behind from area strip mining) Loss of rivers and streams Subsidence: the collapse of land above some underground mines

67 Mining Has Harmful Environmental Effects Major pollution of water and air Acid mine drainage: rainwater seeps through mine and carries H 2 SO 4 to groundwater Effect on aquatic life EPA says 40% of watersheds in US are polluted Large amounts of solid waste 75% of all US solid waste

68 Banks of Waste or Spoils Created by Coal Area Strip Mining in Colorado, U.S.

69 Illegal Gold Mine

70 Ecological Restoration of a Mining Site in New Jersey, U.S.