Lithosphere 2: Tectonics
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This document discusses plate tectonics and the movement of tectonic plates. It provides evidence that supports plate tectonics including: the fit of continental landmasses, matching rock and fossil distributions, and magnetic reversals recorded in ocean crust. It describes the three main plate boundaries and associated landforms: divergent boundaries form mid-ocean ridges and rift valleys, convergent boundaries result in subduction zones and volcanic mountain ranges, and transform boundaries create strike-slip faults. Earthquakes and tsunamis are hazardous events caused by the movement and interactions of tectonic plates. Volcanoes form at plate boundaries and hotspots as magma rises up due to pressure in the crust and mantle.
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Lithosphere 2: Tectonics
- 1. LITHOSPHERE 2 Tectonics ppt. by Robin D. Seamon
- 2. Plate Tectonics VOCABULARY: Continental Drift Alfred Wegner Plate tectonics asthenosphere mantle convection ridge push slab pull deformation magnetic reversals sea floor spreading normal fault reverse fault
- 3. Continental Drift: 1912 Alfred Wegner proposed the idea that the continents were moving away from one another, breaking from one giant protocontinent he named (Pangaea); he but didn’t know why. Today we know that the Earth’s plates float upon the semi-liquid mantle and move due to: The Lithosphere moves & changes.
- 4. http://www.bucknell.edu/x17758.xml Plate Tectonics- theory that the Earth’s lithosphere is composed of 10+ plates that fit together like a puzzle • plates move about 5 cm a year
- 7. The plates move slowly on the upper mantle (asthenosphere) http://kids.britannica.com/comptons/art-156130/A-diagram-shows-the-relationship- between-volcanic-activity-and-Earths
- 8. Movement is caused by mantle convection inside the Earth • Hot, less dense fluids go up while cold, more dense ones go down
- 9. ridge push: sliding plate force; occurs at mid- ocean ridges; caused by gravitational force • spreading happens at the hot magma exit; less dense = greater volume = higher elevation than the cooler ocean floor beside it • As plate moves from the boundary, it also cools, condenses & sinks, creating a SLOPE • lithosphere slides down • the PUSH is applied to the tectonic plate due to gravity
- 10. slab pull: part of the tectonic process caused by subduction • weight of cold, dense oceanic plate dropping under another plate • PULLS the oceanic plate down into the mantle
- 12. Continental “fit” The continents look like they fit together like a puzzle EVIDENCE:
- 13. Correlation of rocks & minerals Coastal regions of different continents have the same rocks & minerals EXAMPLE: Rocks in the Uwharries of NC near Albemarle are of the same rhyolite found on the western coast of Africa EVIDENCE:
- 14. Correlation of fossils Coastal regions of different continents have the same fossils EXAMPLE: fossils of ancient species crossing continents EVIDENCE:
- 15. Finding fossils in unusual locations If we find fossils of a species unable to live in that location today, the plates must have moved EXAMPLE: whale & marine fossils found in Andes mountains EVIDENCE:
- 17. Ocean Floor Evidence • Age of rocks get older away from the divergent boundary • Magnetic Reversals recorded in ocean floor match on opposite sides of the divergent boundary EVIDENCE:
- 18. EVIDENCE: Crustal deformations • Faulting normal fault: hanging wall move down reverse fault: hanging wall moves up
- 19. Plate Interactions VOCABULARY: Continental crust Oceanic crust convergent boundary divergent boundary transform boundary subduction uplift compression tension shear ridge trench rift
- 20. • Two Types of Crust • Float on the asthenosphere Oceanic Crust Density: 2.7 g/cm3 -Cooler -Sinks below continental crust Continental Crust Density: 3.0 g/cm3 -Warmer GRANITE BASALT
- 21. Convergent boundaries- plate boundaries where the force of compression pushes two plates together Divergent boundaries- plate boundaries where the tension pulls plates away from one another Transform boundaries- plate boundaries where one plate slides past another plate through shearing Which subducts? Continental vs. Oceanic What happens in the space? What happens at these faults?
- 22. CONVERGENT BOUNDARIES: Forms volcanic mountain range, trench & sudden earthquakes OCEAN CRUST & CONTINENTAL CRUST SUBDUCTION UPLIFT FORCE: compression
- 24. CONVERGENT BOUNDARIES: Forms oceanic trench & volcanic island chain OCEAN CRUST & OCEAN CRUST SUBDUCTION FORCE: compression
- 26. CONVERGENT BOUNDARIES: Forms mountains CONTINENTAL CRUST & CONTINENTAL CRUST SUBDUCTION UPLIFT FORCE: compression
- 27. Folded Mountains http://freddoty.com/folded-mountains Near the Sullivan River in the Canadian Rockies The Cape Fold Belt Mountains, S Africa http://www.geocaching.com/geocache/GC2CEJP_steytlerville-arch?guid=ff36205a-b979-422c-8266-f7f83ec4d884 FORCE: compression
- 28. DIVERGENT BOUNDARIES: Creates sea-floor spreading: Mid-Atlantic Ridge FORCE: tension OCEAN CRUST & OCEAN CRUST
- 30. DIVERGENT BOUNDARIES: Forms rifts & normal faults: CONTINENTAL CRUST & CONTINENTAL CRUST FORCE: tension Iceland Rift Valley Rift
- 33. TRANSFORM BOUNDARIES: Creates earthquakes: San Andreas Fault CONTINENTAL CRUST & CONTINENTAL CRUST FORCE: shear
- 34. EARTHQUAKES VOCABULARY: earthquake tsunami focus initiation epicenter split seismograph amplification Richter Scale seismic waves P-wave S-wave surface wave shadow zones National Earthquake Information Center Global Seismographic Network Pacific Tsunami Warning Center
- 35. Earthquakes: tension builds up at plate boundaries until the plates slip & tension is released- we feel earthquakes
- 36. • Pressure builds within the crust at the focus and suddenly breaks along a fault • The sudden release of energy causes seismic waves that make the ground shake • epicenter: place on the surface above the focus
- 37. Seismograph- strength of an earthquake is measured with this tool that records the vibrations from sensors placed in the earth http://sydney.edu.au/science/uniserve_science/school/Seismograph/menu.html http://sydney.edu.au/science/uniserve_science/school/Seismograph/menu.html
- 39. Seismic waves: waves of energy are radiated from an earthquake as both body & surface waves; 2 kinds: BODY WAVES travel through earth’s inner layers; faster; arrive first 1. P-wave- primary wave; compressional wave; FIRST WAVE: fastest
- 40. BODY WAVE 2. S-wave- SECOND WAVES slower; can only move through solid rock (not liquid) (this is why scientists deduce the earth’s outer core is liquid) • moves particles up and down or side to side perpendicular to the direction the wave is traveling
- 41. SURFACE WAVES travel only through the crust; • lower frequency; seismographs pick up • damaging waves, sending movement in any direction on the surface; tearing apart structures • deeper earthquakes are less destructive
- 42. Shadow zones- places on Earth’s surface that will not receive seismic waves because of density of material • S-waves are absorbed by the liquid outer core • P-waves care refracted by the liquid outer core ANIMATION
- 44. • Closer a seismic station is to the epicenter 1. The sooner the P-wave will arrive 2. The smaller the difference between P & S waves Determining distance from the Epicenter
- 45. Measure the distance between the first p wave and the first s wave for each station. 1. Which is the closest station? CLOSEST 2nd CLOSEST FARTHEST
- 46. Earthquake Monitoring • National Earthquake Information Center- US (NEIC) determines size & location of significant earthquakes worldwide & sends information out, & maintains a database • Global Seismographic Network (GSN) worldwide seismic network
- 48. Locating the epicenter Determining the location requires distances from three stations. • This will determine the location on a circle with the radius being the distance from that station to the epicenter. • Using data from 3 stations, scientists can triangulate where the epicenter is: • Where the 3 circles intersect = epicenter
- 49. Deadly Hazards • Shaking ground causes buildings, roads and bridges to shake, roofs cave in • Poorly constructed buildings in underdeveloped countries, especially devastating Haiti Earthquake 2010 Magnitude 7.2 230,000 died
- 50. 15,900 + died Japan Earthquake Pictures, Video (9 min) Tohoku Earthquake, Japan 2011 Magnitude 9.1
- 51. Causes of Earthquakes: 1. natural pressure buildup 2. groundwater extraction 3. wastewater injection Destruction dependent upon: 1. Intensity & duration of the vibrations 2. Nature of the material where a structure is built 3. Design of the structure
- 52. Earthquake Protection • Build on stable ground • Use modern earthquake-stable designs for houses and bridges
- 53. IN HOME: seek cover against an interior wall; protect head; avoid mirrors/windows & tall furniture
- 54. Tsunami: when an earthquake or volcanic eruption happens under the ocean 1. Initiation: under-ocean earthquake 2. Split: created wave splits: one moving towards ocean, one towards shore 3. Amplification: front of wave gets taller as it moves toward shore
- 55. Deadly Hazards • Speeds faster than a jet liner • Heights rise 40 feet or more before crashing on shore • 50,000+ people killed this century • 1998 Paupa New Guinea earthquake: 2,200 killed
- 56. • On shore, a person would see the water receding from shoreline as it gathers with the upcoming tidal wave.
- 57. • Pacific Tsunami Warning Center- 1948; collects seismic data from 26 member countries; keeps watch for suspicious shaking that might trigger tsunamis; • Palmer, Alaska- warning center that monitors coasts specific to British Columbia, Washington, Oregon, & California • When an earthquake of 7/5 magnitude or greater near/under the ocean occurs, these warning centers send out initial alerts to all local authorities within 3 hours of tsunami travel time • Local authorities decide on evacuation plans
- 62. VOLCANOES VOCABULARY: volcano shield volcano cinder cone volcano composite volcano caldera Ring of Fire hotspot lava lahar ash acid plumes glass shards
- 63. Pressure under the crust becomes great within a magma chamber & must come out… volcanoes Volcanoes: cracks in the crust where lava flows 1. shield volcanoes 2. cinder cone volcanoes 3. composite volcanoes
- 64. Mauna Kea, Hawaii (shield volcano) http://www.uhh.hawaii.edu/~csav/gallery/decker/hawaii_mauna_kea.php http://www.the-vu.com/2010/05/mauna-kea-in-hawaii-driving-to-the- summit-of-this-grand-volcano/ Shield volcano: layers of lava released from non- explosive eruptions Hawaiian islands are on a hot spot in the center of the Pacific plate
- 65. Paricutin, Mexico photo2.si.edu/mexvolc/volcmex. htm Cinder cone volcano: pyroclastic material- dust & ash explodes out
- 66. Mt. Fuji Mount St . Helens ruby.colorado.edu/.../Volcanix/Volc anix.html Composite volcano: pyroclastic explosions followed by slower, longer flowing-lava (Mt. St. Helens
- 67. Caldera: large, semicircular pit that forms when the chamber supplying magma to a volcano partially empties, then the roof collapses; sinks the ground thinkgeoenergy.com/archives/747
- 69. Ring of Fire Major area in Pacific Ocean basin where many earthquakes and volcanic eruptions occur
- 70. Yellowstone Volcano, Wyoming Enormous caldera & super-volcano under the surface • 40 mile crater • last eruption: 640,000 ya • 1000-2000 earthquakes a year (most below 3 magnitude) • an eruption would be 1000X more powerful than Mt St. Helen’s in 1980 • hydrothermal water features are evidence it is still active • most scientists believe that weeks of warning signs will alert us; 1/700,000 chance a year it will erupt CURRENT CONDITIONS LINK:
- 71. Yellowstone Hotspot hotspot- thermally expanded buoyant mantle that lifts an overlying plate -used to track motion of tectonic plates: hot plate stays put as plate moves across it
- 72. Craters of the Moon National Monument, Idaho -final stage of the Yellowstone hotspot volcanism -result of volcanic flow and a rift valley (62 miles in the park)
- 76. VOLCANIC GEOHAZARDS • lava- magma that reaches the surface
- 77. GEOHAZARDS • lahar- destructive mudflow on the slopes of a volcano
- 78. GEOHAZARDS • ash- volcanic ash clouds the sky and adds to acid rain & air pollution Ontake, Japan 2014
- 79. GEOHAZARDS • acid plumes & glass shards – sulfur dioxide gas & very fine glass shot into the sky as Mt. Kiauea volcano vents 7/2018 VIDEO 1 min
- 80. Mt. Saint Helens, Washington
- 83. • Scientists study and monitor seismic activity at a volcanic hot zone • In scientific observatories & through field work, scientists look for warning signs of an eruption • small earthquakes • inflation/swelling of the land • increased emission of heat/gas from vents Kilauea Observatory, HI
- 84. Official Volcano Warnings • color codes & alert levels • specific for each volcano • warning systems are based on probability of eruption
- 85. Safety After a Volcano • cover mouth &nose • wear goggles/protect eyes • cover skin • clear roofs from heavy ash