plate tectonics :// 2009
TRANSCRIPT
Plate Tectonicshttp://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
Crust
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
Mantle
The Core• Below the mantle and to the
center of the Earth• Outer Core-layer of molten
metal, which behaves like a liquid.
• Inner Core – is a dense ball of solid metal-b/c the extreme pressure squeezes the atoms of iron and nickel so much that they cannot spread out and become a liquid.
• Core is believed to be mostly Iron, smaller amounts of Nickel, almost no Oxygen, Silicon, Aluminum, or Magnesium
“Both the outer & inner core together are just slightly smaller than the moon.”
Core
Earth’s Magnetic Field
A. Currents in the liquid outer core force the solid inner core to spin.
B. The inner core inside the Earth, spins at a slightly faster rate than the rest of the planet.
C. The spinning movement—creates the Earth’s magnetic field, which is a force that causes the planet to act like a giant bar magnet.1. Like a magnet, Earth’s magnetic field
has north & south poles.
Conclusion
Plate Tectonics
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
Plates
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 Pangea, Greek for “all Earth”
245 Million years ago
Split again – Laurasia & Gondwana 180 million years ago
Continental Drift
Evidence of Pangea
Ocean Floor
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
Clues about Ocean Floors(Expedition)
How Plates Move
http://pubs.usgs.gov/gip/dynamic/unanswered.html
Convection Currents
Different Types of Boundaries
http://pubs.usgs.gov/gip/dynamic/understanding.html
Divergent Boundary – Arabian and African Plates
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 – 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 Boundaries - Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Transform Boundary – San Andreas Fault
www.geology.com
Review
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