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Key concepts. Earth Composition. Crust: thinnest layer, least dense Mantle: upper most part is able to flow very slowly (asthenosphere) Core: Lower area is a solid and outer area is a liquid. Makes up 1/3 of Earth’s mass. The hottest layer with the most pressure.

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Key concepts

Earth Composition

Crust: thinnest layer, least denseMantle: upper most part is able to flow very slowly (asthenosphere)

Core: Lower area is a solid and outer area

is a liquid. Makes up 1/3 of Earth’s mass.

The hottest layer with the most pressure.



Key concepts

  • Evidence of “continental drift”—

  • .

  • Physical fit of continents

  • Fossil evidence

  • Measurements of movement

  • Rock layer sequences

  • Glacial evidence

Alfred Wegener


What is the theory of continental drift
What is the theory of continental drift?

  • the idea that the continents were once all joined together in one super-continent called Pangaea and slowly moved to their current positions




Shoreline Fit of the Continents

http://www.abdn.ac.uk/zoohons/lecture1/img008.GIF


Fossil evidence
Fossil Evidence

The fossils from the exact same animals are found on continents separated by vast oceans.



Glacier evidence
Glacier Evidence

Glaciers scars are found on continents which are today too warm for glaciers.



You may wonder
You may wonder…

Why are the continents moving?


Seafloor Spreading

The oceans are widening along the mid-ocean ridges.



Key concepts ocean floor.

Plates—continental crust, oceanic crust

Features—faults, trenches, mid-ocean ridges, folded mountains, hot spots, volcanoes

Related actions —earthquakes, volcanic activity, seafloor spreading, mountain building, convection in mantle.


The earth s lithosphere is broken into huge sections called plates that are in constant motion
The earth’s lithosphere is broken into huge sections called plates that are in constant motion.


What are the plates made of
What are the plates made of? called plates that are in constant motion.

  • Ocean plates are made of basalt.

  • Continental plates are made of granite.


Divergent plate boundaries
Divergent Plate Boundaries called plates that are in constant motion.

Two land or ocean plates move apart in opposite directions. Magma flows to the surface between them creating new crust.


Mid atlantic ridge divergent boundary
Mid-Atlantic Ridge = Divergent Boundary called plates that are in constant motion.


Http www geo lsa umich edu crlb courses 270 lec12 spreexamples jpeg
http://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeghttp://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg


Iceland a continent directly over the mid atlantic ridge
Icelandhttp://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg – a continent directly over the Mid-Atlantic Ridge


Subduction zones
Subduction Zoneshttp://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg

  • An ocean plate and a continental plate hit head-on. The ocean plate subducts under the continent forming a trench. The subducting plate melts. Magma rises to the surface creating a string of volcanic mountains parallel to the shoreline.


Andes mountains
Andes Mountainshttp://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg

Subduction zones form chains of volcanic mountains along the shoreline.


Collision zones
Collision Zoneshttp://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg

Two continents hit head-on, crinkling up the land into a high mountain chain.


India s collision with asia
India’s Collision with Asiahttp://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg

Himalayas


The Himalayas Are Born…http://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg


Island arcs
Island Arcshttp://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg

Two ocean plates hit head-on. One ocean plate is forced to subduct under the other forming an ocean trench. The subducting plate melts. Magma rises to the surface forming a string of volcanic islands parallel to the trench.


The aleutian islands
The Aleutian Islandshttp://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg


Key conceptshttp://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg

Forces—tension, compression shearing

Ask a Geologist

Ask an earth scientist


How does tectonic activity affect the earth s crust
How does tectonic activity affect the earth’s crust?http://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg

  • Builds mountains

  • Creates deep ocean trenches

  • Causes earthquakes

  • Create volcanoes


Ocean trenches
Ocean Trencheshttp://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg

http://www.nhusd.k12.ca.us/ALVE/wow/Ocean/seafloor.gif


Volcanoeshttp://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg


Most volcanoes occur at plate boundaries
Most volcanoes occur at plate boundaries…http://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/spreexamples.jpeg


http://www.thirteen.org/savageearth/hellscrust/assets/images/ringoffire.jpghttp://www.thirteen.org/savageearth/hellscrust/assets/images/ringoffire.jpg


Real-world contexts:http://www.thirteen.org/savageearth/hellscrust/assets/images/ringoffire.jpg

Recent patterns of earthquake and volcanic activities;

maps showing the direction of movement of major plates

and associated earthquake and volcanic activity

Compressional boundaries: folded mountains, thrust faults, trenches, lines of volcanoes (e.g. Pacific “ring of fire”)

Tensional boundaries: mid-ocean ridges, rift valleys

Shearing boundaries: lateral movement producing

faults (e.g. San Andreas Fault).


http://www.gfz-potsdam.de/pb2/pb22/projects/mamba.htmlhttp://www.thirteen.org/savageearth/hellscrust/assets/images/ringoffire.jpg


Resources
Resourceshttp://www.thirteen.org/savageearth/hellscrust/assets/images/ringoffire.jpg

  • http://www.calstatela.edu/faculty/acolvil/plates/pangaea.jpg

  • http://platetectonics.pwnet.org/img/wegener.jpg

  • http://home.tiscalinet.ch/biografien/images/wegener_kontinente.jpg

  • http://library.thinkquest.org/17457/platetectonics/comic.jpg

  • http:[email protected]/carlsberg/images/fossil_correlation_lge.jpg

  • http://earthobservatory.nasa.gov/Library/Giants/Wegener/Images/plate_boundaries.gif

  • http://www.calstatela.edu/faculty/acolvil/plates/atlantic_profile.jpg

  • http://pubs.usgs.gov/publications/graphics/Fig16.gif

  • http://cps.earth.northwestern.edu/SPECTRA/IMG/basalt.png

  • http://cc.usu.edu/~sharohl/granite.jpg

  • http://tlacaelel.igeofcu.unam.mx/~GeoD/figs/tgondvana_ice.jpg

  • http://www.physics.uc.edu/~hanson/ASTRO/LECTURENOTES/F01/Lec11/Pangaea.gif

  • http://www.poleshiftprepare.com/glacial_striation.jpg


  • http://www.ggs.org.ge/plates.jpghttp://www.thirteen.org/savageearth/hellscrust/assets/images/ringoffire.jpg

  • http://earth.geol.ksu.edu/sgao/g100/plots/1008_world_volc_map.jpg

  • http://www.aeic.alaska.edu/Input/affiliated/doerte/personal/aleutians/ak_map_big.jpg

  • http://www.4reference.net/encyclopedias/wikipedia/images/Aleutians_aerial.jpg

  • http://www.avo.alaska.edu/gifs/2-3/02-95-03.jpg

  • http:[email protected]/carlsberg/images/island_arc.jpg

  • http://nte-serveur.univ-lyon1.fr/nte/geosciences/geodyn_int/tectonique2/himalaya/images/Fig5a_inde.gif

  • http://terra.kueps.kyoto-u.ac.jp/~sake/himalaya.jpg

  • http://www.andes.org.uk/peak-info-5000/sabancaya.jpg

  • http://www-step.kugi.kyoto-u.ac.jp/~keizo/photos/andes.JPG

  • http://www.letus.northwestern.edu/projects/esp/top10/andespage/andesphysical.jpg

  • http:[email protected]/carlsberg/images/atlantic_tectonics%20.jpg


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