Plate Tectonics

Global Plate Boundaries © 2011 Pearson Education, Ic.

Plate Boundaries There are 3 main plate boundaries: 1) Convergent Boundary 2) Divergent Boundary 3) Transform Boundary

Types of Plate Boundaries

Draw With Me 

1. Convergent Boundaries Occurs when 2 plates collide. Oceanic plate is denser (3.2 g/cm3), faster and thinner - it is usually forced under the continental plate (2.8 g/cm3).

The rock in the Oceanic plate melts as the plate sinks The rock in the Oceanic plate melts as the plate sinks. The melted rock rises up causing volcanic eruptions. The area of convergence is called a SUBDUCTION ZONE. When two continental plates collide: They are the same density. This causes the plates to fold and bend (mountain building) as well as earthquakes.

Convergent Boundary Plates move toward each other Oceanic crust destroyed Ocean trench Volcanic arc

Example of a Convergent Plate Boundary South America: Oceanic Nazca Plate is colliding into the South America plate. Producing the Andes Mountains (volcanoes along the mountain crest) and formed a deep trench off the coast in the Pacific Ocean. http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_subduction.html

© 2011 Pearson Education, Inc.

Convergent Boundaries

Let’s do some drawing!

Divergent Plate Boundaries Plates are being pulled apart by convection currents in the mantle. As the plates separate along the boundary, they crack into faults and blocks. Magma from the mantle rises through the cracks. This cools and new crust is formed along the boundary. Earthquakes occur along the faults, and volcanoes form where the magma reaches the surface.

Mid Atlantic Ridge Mid-Atlantic Ridge is a Divergent Plate Boundary. Over 15 000 km long. Average height of volcanoes - 3 km. http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_seafloorspreading.html

Age of Ocean Floor

Example of a Divergent Plate Boundary http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm#1 The Process of Rifting

Divergent Boundary Rift valley Plates move apart Mid-ocean ridge New ocean floor created

Sea Floor Diagram © 2011 Pearson Education, Inc.

Generation of a Divergent Boundary

Types of Spreading Centers

Sea Floor Spreading Mid-ocean ridge – spreading center Subduction zones – oceanic trench site of crust destruction http://www.watchknowlearn.org/Video.aspx?VideoID=698&CategoryID=2464

Earthquakes As Evidence Earthquake activity mirrors tectonic plate boundaries. © 2011 Pearson Education, Inc.

Global Distribution of Earthquakes

Transform Boundary Places where plates slide past each other sideway. Transform boundaries are not marked by spectacular surface features, but their sliding motion causes lots of earthquakes. The slice of California to the west of the fault is slowly moving north relative to the rest of California.

The Problems of Haiti…

Interactive Plate Tectonic Map http://geology.com/plate-tectonics.shtml Go to the following site and complete the activity!

Earth’s Magnetic Field http://science.howstuffworks.com/environmental/planet-earth-videos-playlist.htm#video-29143

HOT SPOT VOLCANOES http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm#1 Animation

Examples of Plate Boundaries

Transform Boundary Features Oceanic Transform Fault – ocean floor only Continental Transform Fault – cuts across continent All transform faults occur between mid-ocean ridge segments.

Global Hotspot Locations

Hawaiian Island – Emperor Seamount Nematath

Plate Tectonics Features Seamounts Rounded tops Tablemounts or guyots Flattened tops Subsidence of flanks of mid-ocean ridge Wave erosion may flatten seamount

Detecting Plate Motion with Satellites

World Map 50 million Years in Future

Coral Reef Development Fringing reefs – develop along margin of landmass Barrier reefs – separated from landmass by lagoon Atolls – reefs continue to grow after volcanoes are submerged

Coral Reef Development