Plate TectonicsLiz LaRosa for use with my 5th Grade Science Class

http://www.middleschoolscience.com 2009

Earth’s LayersThe Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed.

This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle.

The Crust

• Outermost layer• 5 – 100 km thick• Made of Oxygen, Silicon, Aluminum

The Mantle

• Layer of Earth between the crust and the core

• Contains most of the Earth’s mass

• Has more magnesium and less aluminum and silicon than the crust

• Is denser than the crust

The Core

• Below the mantle and to the center of the Earth

• Believed to be mostly Iron, smaller amounts of Nickel, almost no Oxygen, Silicon, Aluminum, or Magnesium

Continental Drift

http://members.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml

Alfred Wegener 1900’sContinents were once a single land mass that drifted apart.

Fossils of the same plants and animals are found on different continents

Called this supercontinent Pangaea, Greek for “all Earth”

245 Million years ago

Split again – Laurasia & Gondwana 180 million years ago

Evidence of Pangea

Tectonic Plates

Plate Tectonics

• Greek – “tektonikos” of a builder• Pieces of the lithosphere that move around• Each plate has a name• Fit together like jigsaw puzzles• Float on top of mantle similar to ice cubes

in a bowl of water

Plate tectonics

• http://www.youtube.com/watch?v=1-HwPR_4mP4• (7min 40 sec)

How Plates Move

http://pubs.usgs.gov/gip/dynamic/unanswered.html

How Plates Move

• Convection current – movement in a fluid or air due to uneven cooling1. the denser plate moves below into the earth

2. heated to liquid

3. decreases in density

4. rises to surface again

5. it cools and increases in density.

Different Types of Boundaries

http://pubs.usgs.gov/gip/dynamic/understanding.html

Divergent Boundary

• Regions where two tectonic plates are moving apart

• Occurs between oceanic plates, continental plates, and a combination of the two

Divergent Boundary – Arabian and African Plates

Divergent Boundary – Iceland

http://pubs.usgs.gov/gip/dynamic/understanding.html

Divergent Boundary – Oceanic (oceanic ridge)

http://www.geology.com

Divergent Boundary – Continental(rift valley)

http://www.geology.com

Divergent Features

• Rift valley – a long, narrow depression that forms when continental crusts begins to separate

Divergent: Sea Floor Spreading

Sea Floor Spreading

• Mid Ocean Ridges – underwater mountain chains that run through the Earth’s Basins

• Magma rises to the surface and solidifies and new crust forms

• Older Crust is pushedfarther away from the ridge

Sea-floor spreading

http://www.youtube.com/watch?v=GyMLlLxbfa4

Convergent Boundary

• Border formed from by the direct collision of two plates

Convergent Boundary – Indian and Eurasian Plates

Convergent Boundary – Oceanic & Continental

http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Convergent Boundary – Oceanic & Oceanic

http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Convergent features

• Subduction zone – one plate moves under the other – Oceanic is more dense and moves below

continental crust at subduction zones

• Ocean trench - an elongated, sometimes arc-shaped depression in the seafloor that can extend for thousands of kilometers and is the deepest part of the ocean basin as continental and oceanic plates converge

Convergent features

• Island arc – chain of volcanic islands formed along an ocean trench

Convergent Boundaries - Continental

http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Transform (fault) Boundary

• Boundary formed where two plates slide past each other

Transform Boundary – San Andreas Faulthttp://mass.pbslearningmedia.org/resource/ess05.sci.e

ss.earthsys.thrustfault/earthquakes-los-angeles/

www.geology.com

Review

• Name the 3 main layers of the Earth• What is a tectonic plate?• What was Pangea?• What is Sea-Floor spreading?• Name the three different types of plate

boundaries and one location on Earth for each one