Plate Tectonics Liz LaRosa for use with my 5th Grade Science Class http://www.middleschoolscience.com 2009

Earth’s Layers The 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 Is denser than the crust

Earth Layers Asthenosphere: from greek word “weak”. Zone of weak, easily deformed rock in the upper mantle. Lithosphere: from greek word “stone”. Floats on the asthenoshpere Includes all of the crust and part of the upper mantle. Cool rigid portion of the Earth Divided into seven major plates…

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

Apple Demo Compare the layers of the Earth to this apple.

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http://www.youtube.com/watch?v=RiHRI_Z2Kgs&feature=related http://www.brainpop.com/science/earthsystem/earthsstructure/preview.weml

Tectonic Plates

Plate Tectonics Greek – “tektonikos” of a builder Theory scientists use to explain plate movement 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 Plates in constant motion….very slow Moves only few cm per year Boundaries where plates meet are usually the site of earthquakes and volcanoes Movement of plates causes Earth’s surface to change constantly and dramatically (crumpling rocks, folding them, stretching and cracking) Moves continents around globe Causes earthquakes and volcanic eruptions

Convection Transfer of heat Cannot take place without a source of heat. Ex. Hot water is less dense than cold water and rises, causing convection currents which transport energy.

How Plates Move http://pubs.usgs.gov/gip/dynamic/unanswered.html

Plate Tectonics Plates move away from each other along divergent boundaries Plates collide along a convergent boundary Plates grind past each other along transform fault boundaries These plate movements have produced most of the world’s volcanoes, earthquakes, high mountain ranges, and deep ocean trenches

Continental Drift Alfred Wegener 1900’s Continents were once a single land mass that drifted apart. Fossils of the same plants and animals are found on different continents Called this supercontinent Pangea, Greek for “all Earth” 245 Million years ago http://members.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml

Remember The continents and oceans are on Earth’s plates. Because plates move, the continents we live on today were different places in the past. They will continue to move in other positions in the future!

Evidence of Pangea

Discussion How were similar rock types used to support the continental drift hypothesis? Similar rock types in mountains such as the Appalachian Mountains and the Caledonian Mountains suggest that North America and northern Europe were at one time connected as part of a single landmass. Likewise, similar volcanic rocks in Africa and South America suggest that these two continents were also joined.

http://www.brainpop.com/science/earthsystem/platetectonics/

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 hardens and new crust forms Older Crust is pushed farther away from the ridge

http://www.brainpop.com/science/earthsystem/oceanfloor/

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Different Types of Boundaries http://pubs.usgs.gov/gip/dynamic/understanding.html

Divergent Boundary Caused by magma being pushed upward under a plate Magma presses against plate Melts and stretches lithosphere until it cracks Magma flows into the gap and cools to form new crust

Divergent Boundary – Arabian and African Plates Arabian Plate Red Sea African Plate

Divergent Boundary – Iceland http://pubs.usgs.gov/gip/dynamic/understanding.html

Divergent Boundary - Oceanic http://www.geology.com

Divergent Boundary - Continental http://www.geology.com

Convergent Boundary Three kinds of collisions possible Oceanic plate collide with oceanic plate: one of the plates is pushed under the other. The plate that is forced down, melts…creating a trench Two continental plates collide: one forced under other. Plates crumple and fold, forming mountain ranges Oceanic plate collides with continental plate: oceanic plate forced downward. Mountains and volcanoes form along the boundary between plates

FACT 80% of the worlds volcanoes and 90% of all earthquakes occur along convergent boundaries!!!

Convergent Boundary – Indian and Eurasian Plates Indian Plate

Convergent Boundary – Oceanic & Continental http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Convergent Boundary – Oceanic & Oceanic Note – plates are reversed http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Convergent Boundaries - Continental http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Transform Fault Boundaries Two plates move past each other in opposite directions

Transform Boundary – San Andreas Fault www.geology.com

Discussion What is plate tectonics? Plate tectonics is a theory that Earth's surface is made of rigid slabs of rock, or plates, that move with respect to each other. What are Earth's outermost layers called? Earth's outermost layers, which include the crust and the solid, uppermost mantle, make up the lithosphere.

Discussion What are the three types of plate boundaries? Divergent, transform, and convergent are the three types of plate tectonic boundaries. Why do tectonic plates move? The mantle moves horizontally under Earth's plates due to convection currents. Earth's plates carried along by the moving mantle below them.

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FACT 95% of all earthquakes occur at or near the edges of moving plates, along great cracks in Earth’s crust called faults.

Earthquakes As plates continue to move, rocks put under great strain Rocks bend and stretch until they reach their breaking point Suddenly, rocks snap and move into new positions A jolt on energy is released Felt as earthquake Causes tsunami’s

http://www.youtube.com/watch?v=4Xebwzb3dDE http://www.brainpop.com/science/earthsystem/earthquakes/ http://www.brainpop.com/science/earthsystem/tsunami/

Volcanoes A volcano is a mountain that may form around the opening as the lava cinders build up Occurs at plate boundaries (convergent: oceanic/continental)

Formation of Volcanoes Magma, or molten rock beneath Earth’s surface is forced up through an opening in Earth’s surface. Molten rock erupts as lava Hot molten rock is pushed upward to form volcanic mountains

Types of Volcanoes Shield volcano Looks like a warriors shield Long, flat, slightly domed

Types of vocanoes Cinder cone volcano Built up from ashes/cinders and rocks that burst during a violent eruption Rocks fall back to surface, creating a cone.

Types of volcanoes Composite volcano Switches between quiet eruptions of flowing lava and violent eruptions Most powerful type of eruption

http://www.brainpop.com/science/earthsystem/volcanoes/

Discussion How are earthquakes and volcanoes related to the theory of plate tectonics? Most volcanic eruptions and earthquakes occur along plate boundaries.

Amazing sight in the South Pacific

In the South Pacific the water is much warmer than normal In the South Pacific the water is much warmer than normal.  Environmentalists have said that Global Warming causes it.  Other Scientists have noted there is a substantial amount of volcanic activity in that same area.  It has a tendency to warm water, also.  Here’s an interesting set of photos.

August 2006, the yacht 'Maiken' is travelling in the south Pacific when they came across a weird sight...

It was sand in the water, and floating ON TOP of the waves...

This is not a beach, it is volcanic stones floating on the water.

The trail left by the yacht...

And then this was spotted... ash and steam rising from the ocean...

And, while they were watching...

A brand new island formed...

A plume of black ash...

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