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
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 Split again – Laurasia & Gondwana 180 million years ago http://members.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml
Evidence of Pangea
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 pushed farther away from the ridge
Why do plates move?
Convection currents
Convection currents What are they? How do they make plates move? When mantle rocks near the radioactive core are heated, they become less dense than the cooler, upper mantle rocks. These warmer rocks rise while the cooler rocks sink, creating slow, vertical currents within the mantle (these convection currents move mantle rocks only a few centimeters a year). This movement of warmer and cooler mantle rocks, in turn, creates pockets of circulation within the mantle called convection cells. The circulation of these convection cells could very well be the driving force behind the movement of tectonic plates over the athenosphere.
Subduction What is it? One plate sinks underneath the other because it is more dense.
How Plates Move http://pubs.usgs.gov/gip/dynamic/unanswered.html
Convection currents
Destructive vs. Constructive forces Define both of the terms below: Constructive forces- builds the Earth up Destructive forces- Breaks the Earth down
Destructive or constructive? type destructive constructive both Erosion Weathering Deposition Volcano earthquake
Different Types of Boundaries http://pubs.usgs.gov/gip/dynamic/understanding.html
Plate boundaries Transform Plates slide past each other Earthquakes form
Transform Boundary – San Andreas Fault www.geology.com
Plate boundaries Divergent Plates divide In ocean- will be mid-ocean ridges On land- rift valleys Why? As plates spread apart, magma rises through the gap and forms 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 – Indian and Eurasian Plates Indian Plate
Convergent Boundary – Oceanic & Continental http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Plate boundaries Convergent Plates collide (go together) When ocean plates meet continent plates, an ocean trench forms with volcano on the land Why? Ocean plate is more dense than continental and sinks under it into mantle (subduction)
Convergent Boundary – Oceanic & Oceanic Note – plates are reversed http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Plate boundaries Convergent Plates collide (go together) When ocean plates meet ocean plates, an ocean trench forms with magma forming islands Why? The ocean plate that is more dense will sink under the other (subduction)
Convergent Boundaries - Continental http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Plate boundaries Convergent Plates collide (go together) When continent plates meet continent plates, mountains form Why? Continental plates buckle up as they push together
Plate tectonic animations http://www.nature.nps.gov/geology/usgsnps/animate/pltecan.html
Additional activities: Plate tectonics www.brainpop.com Volcanoes http://www.brainpop.com/science/earthsystem/volcanoes/ Earthquake http://www.brainpop.com/science/earthsystem/earthquakes/ Pangaea activity worksheet Plate boundary prediction worksheet