Plate tectonics l.jpg
Sponsored Links
This presentation is the property of its rightful owner.
1 / 71

Plate Tectonics PowerPoint PPT Presentation


  • 145 Views
  • Uploaded on
  • Presentation posted in: General

Plate Tectonics. Continental Drift. Historical Landmass Locations. Fossil Evidence Supporting Plate Tectonics. Developing the Theory. (1) demonstration of the ruggedness and youth of the ocean floor; (2) confirmation of repeated reversals of the Earth magnetic field in the geologic past;

Download Presentation

Plate Tectonics

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Plate Tectonics

Continental Drift


Historical Landmass Locations


Fossil Evidence Supporting Plate Tectonics


Developing the Theory

  • (1) demonstration of the ruggedness and youth of the ocean floor;

  • (2) confirmation of repeated reversals of the Earth magnetic field in the geologic past;

  • (3) emergence of the seafloor-spreading hypothesis and associated recycling of oceanic crust; and

  • (4) precise documentation that the world's earthquake and volcanic activity is concentrated along oceanic trenches and submarine mountain ranges.


Developing the Theory (continued)

  • (1) demonstration of the ruggedness and youth of the ocean floor.

  • (See next slide)


Computer-generated topographic map of Mid-Oceanic Ridge.


Mid-Ocean Ridge


Magnetic striping and polar reversals


Concentration of Earthquakes


Plate Motions

  • There are four types of plate boundaries:

  • Divergent boundaries -- where new crust is generated as the plates pull away from each other.

  • Convergent boundaries -- where crust is destroyed as one plate dives under another.

  • Transform boundaries -- where crust is neither produced nor destroyed as the plates slide horizontally past each other.

  • Plate boundary zones -- broad belts in which boundaries are not well defined and the effects of plate interaction are unclear.


Types of Plate Boundaries


Divergent Boundaries


Mid-Atlantic Ridge Example

Red triangles denote active volcanoes


Aerial view of the area around Thingvellir, Iceland, showing a fissure zone (in shadow) that is the on-land exposure of the Mid-Atlantic Ridge.


Divergent Boundary – East Africa

Map of East Africa showing some of the historically active volcanoes(red triangles) and the Afar Triangle (shaded, center) -- a so-called triple junction (or triple point), where three plates are pulling away from one another


Summit Crater of 'Erta 'Ale (Ethiopia)


Oldoinyo Lengai, erupts in 1966


Convergent BoundariesOceanic-continental convergence


Convergent Boundaries (example)


Oceanic-oceanic convergence


Continental-continental convergence


Continental-continental convergence

The collision between the Indian and Eurasian plates has pushed up the Himalayas and the Tibetan Plateau


Continental-continental convergenceIndian – Eurasian Plates


The Himalayas: Two Continents CollideThe 6,000-km-plus journey of the India landmass (Indian Plate) before its collision with Asia (Eurasian Plate) about 40 to 50 million years ago. India was once situated well south of the Equator, near the continent of Australia.


Transform Boundaries

The Blanco, Mendocino, Murray, and Molokai fracture zones are some of the many fracture zones (transform faults) that scar the ocean floor and offset ridges (see text). The San Andreas is one of the few transform faults exposed on land.


San Andreas fault

Aerial view of the San Andreas fault slicing through the Carrizo Plain in the Temblor Range east of the city of San Luis Obispo.


Plate-boundary Zones


Rates of Motion

  • The Arctic Ridge has the slowest rate (less than 2.5 cm/yr)

  • The East Pacific Rise near Easter Island, in the South Pacific about 3,400 km west of Chile, has the fastest rate (more than 15 cm/yr).


Hotspots: Mantle Thermal Plumes


Prominent Thermal Hotspots


The Long Trail of the Hawaiian Hotspot

Map of part of the Pacific basin showing the volcanic trail of the Hawaiian hotspot-- 6,000-km-long Hawaiian Ridge-Emperor Seamounts chain.


Plate Tectonics & People

  • Natural hazards

    • Earthquakes

    • Volcanic eruptions

    • Tsunamis

  • Natural resources

    • Fertile soils

    • Ore deposits

    • Fossil fuels

    • Geothermal energy


Earthquakes

Aerial view, looking north toward San Francisco, of Crystal Springs Reservoir, which follows the San Andreas fault zone.


Earthquakes (continued)

Map of the San Andreas and a few of the other faults in California, segments of which display different behavior: locked or creeping


Fault Creeping

Left:Creeping along the Calaveras fault has bent the retaining wall and offset the sidewalk along 5th Street in Hollister, California (about 75 km south-southeast of San Jose). Right:Close-up of the offset of the curb.


Earthquakes & Volcanoes

  • Christopherson TextChapter 12 pp 375-end-of-chapter


What Causes Earthquakes?


Epicenter and Focus

  • Focus 

    • Location within the earth where fault rupture actually occurs 

  • Epicenter 

    • Location on the surface above the focus


Types of Faults

Faults are classified on the basis of the kind of motion that occurs on them

  • Joints - no movement

  • Strike-slip - horizontal motion (wrench faults)


Types of Faults

  • Joints - No Movement

  • Strike-Slip - Horizontal Motion (Wrench Faults)


Joints - No Movement


Left Lateral Strike Slip


Right Lateral Strike Slip

San Andreas

21 feet in 1906


Dip-Slip - Vertical MotionNormal Fault (Extension)

Alaska, 1964 - up to 150 Ft


Reverse or Thrust Fault (compression)


Eastern North America Earthquakes 1534-1994


U.S. Earthquakes, 1973-2002


Seismic Risk Level Maps for the U.S.Probable ground acceleration in 50 years. Blue = small, red = large


Seismic Risk Level Maps for the U.S.Probability of Damage in 100 Years. Blue = Negligible, Green = Low, Red = High.


M 7.9 Earthquake on November 3, 2002

  • The largest earthquake known to occur in the world this year struck central Alaska on Sunday, November 3. The epicenter of the Nov. 3 temblor was located approximately 75 miles south of Fairbanks and 176 miles north of Anchorage. It struck at 1:12 PM local time, causing countless landslides and road closures, but minimal structural damage and amazingly few injuries and no deaths.


M 7.9 Earthquake on November 3, 2002

  • Overall, the geologists found that measurable scarps indicate that the north side of the Denali fault moved to the east and vertically up relative to the south. Maximum offsets on the Denali fault were 22 feet at the Tok Highway cutoff, a road that goes from Tok to Glenallen and intersects with the Alaska Highway, and were 6.5 feet on the Totschunda fault.

  • This earthquake is one of the largest ever recorded on U.S. soil and the largest seismic event ever recorded on the Denali fault system.


Denali Fault Earthquake


Rock Avalanches Across Black Rapids Glacier


Alaska Earthquake Pictures Taken by Local Resident


Alaska Earthquake Pictures Taken by Local Resident


Alaska Earthquake Pictures Taken by Local Resident


Alaska Earthquake Pictures Taken by Local Resident


Alaskan Pipeline


Northway Road - 4th of November 2002


Road Offset, Richardson Hwy


Volcanoes


Two expressions of volcanic activity.


Volcanic fountaining in Hawaii.


Kilauea landscape.


Mt.Etna, Sicily – July 2001


Mt.Etna, Sicily – July 2001


Mt.Etna, Sicily – July 2001


Mt.Etna, Sicily – July 2001


Mt.Etna, Sicily July 2001


Mt.Etna, Sicily – July 2001


Mt.Etna, Sicily – July 2001


  • Login