Do First Actions: Turn in yesterday’s lab Questions: Why does an oceanic plate slide under a continental plate when they converge? What is the above process called?

Agenda Plate Interaction Notes Why Plates Move the Way they Do Video Review

What are Plates? Lithosphere is broken in parts called plates. The Earth’s crust and upper mantle=lithosphere

Types of Plates Oceanic plates - plates below the oceans Continental plates - plates below the continents Which type of plate is more dense?

Plate Tectonics Plate tectonics refers to the movement of plates on top of the asthenosphere (putty layer), which is a part of the mantle. There are 12 plates moving in various directions very slowly (2-5 cm a year) The interactions of these plates create structures or “tectonic features”

Plate Tectonics

Why Plates Move Convection Currents 2. Gravity Hot magma in the Earth moves toward the surface, cools, then sinks again Causes the asthenosphere to move which forces the plates on top of them to move like an object on a treadmill The individual currents are known as convection cells 2. Gravity Pushes down on the plates Forces the denser plates to sink

Why Plates Move tinyurl.com/k8jaj7p

Plate Boundaries ↑↓     1. Divergent Plate boundaries are where plates touch There are three types of movements at plate boundaries: 1. Divergent   2. Convergent   3. Transform ↑↓

Three Basic Types of Plate Boundaries Using hands to show relative motion Divergent Transform Convergent Video: Plate Boundaries— www.iris.edu/hq/programs/education_and_outreach/videos Plates can have three kinds of motion across boundaries: [note video lecture on next slide] They can move away from each other like at a divergent boundary (= spreading ocean ridge or a rift zone). Or use parallel hands like the transform beginning hands and move them apart allowing the magma (thumbs) to come up. 2. They can move toward each other to make a convergent boundary. 3. They can slide past each other horizontally at a transform boundary. When two plates carrying continents converge, a continental collision occurs where continental crust piles up. Continental crust is lower density than mantle rocks, so continental rocks cannot be “subducted” into the mantle. If continental rocks are pushed into the mantle, they will soon pop up again. This is like trying to push a piece of styrofoam into a swimming pool. You can push the styrofoam into the water (with some force) but, when you let it go, it pops back to the surface because it is much less dense than the water on which it floats. ACTIVITY: Teaching about Plate Tectonics Using Foam Models: Download FoamFaultModel_Activity.pdf from Animations Page: http://www.iris.edu/hq/programs/education_and_outreach/animations/2 Graphics from “This Dynamic Planet, World Map of Volcanoes, Earthquakes, Impact Craters, and Plate Tectonics.” A Smithsonian, USGS, US Naval Research lab publication. You can find this at http://www.minerals.si.edu/tdpmap/ .ﾊCopyright protected: The content may only be used for personal, educational or noncommercial purposes; USGS Graphics

Divergent Boundaries   What’s happening? Boundary between two plates that are moving apart or rifting RIFTING causes SEAFLOOR SPREADING What features are formed? Mid-ocean ridges (ocean) rift valleys (continent) fissure volcanoes

East African Rift Valley

Convergent Boundaries   What’s happening? Boundaries between two plates that are colliding There are three types: Oceanic – Continental Oceanic – Oceanic Continental - Continental

Type 1: Oceanic - Continental What’s happening? Oceanic plate colliding with a less dense continental plate What features are formed? Subduction Zone: where the denser plate slides under the less dense plate forming a trench Where plates are recycled into the mantle VOLCANOES occur at subduction zones

Andes Mountains, South America

Type 2: Oceanic - Oceanic What’s happening? Oceanic plate colliding with another oceanic plate What features are formed? Subduction Zone or Trench Volcanos

Aleutian Islands, Alaska

Type 3: Continental – Continental What’s happening? A continental plate colliding with another continental plate What features are formed? Mountains

Transform Fault Boundaries What’s happening? Boundary between two plates that are sliding past each other What features are formed? Earthquakes

San Andreas Fault, CA

Three Basic Types of Plate Boundaries Divergent Transform Convergent Animations: Divergent and Convergent Plate Boundaries http://www.iris.edu/hq/programs/education_and_outreach/animations Video lecture by Dr. Robert Butler:Types of Boundaries.mov on the site http://www.iris.edu/hq/programs/education_and_outreach/videos Plates can have three kinds of motion across boundaries [more details on next slides]: 1. They can move away from each other like at a divergent boundary (= spreading ocean ridge or a rift zone); 2. They can move toward each other to make a convergent boundary. 3. They can slide past each other horizontally at a transform boundary. Graphics from “This Dynamic Planet, World Map of Volcanoes, Earthquakes, Impact Craters, and Plate Tectonics.” A Smithsonian, USGS, US Naval Research lab publication. You can find this at http://www.minerals.si.edu/tdpmap/ .ﾊCopyright protected: The content may only be used for personal, educational or noncommercial purposes; USGS Graphics

Video Watch the short video to understand why and how plates move

DYL What are the 3 types of plate interactions? What type of interaction is shown in the picture below?

Resources http://pnsn.org/outreach/about-earthquakes/plate-tectonics http://www.planetseed.com/files/flash/science/features/earth/living planet/plate_boundaries/en/index3.html?width=570&height=475&p opup=true