Continental Drift: the concept that continents can break up and move across the earths surface

few cm per year.

techtoniocs: the study of large scale movement and deformation of the earth's outer layers

plate techtonics: realtes to techtonics and to the existence and movement of plates over a weak or partly molten layer of the earth's upper mantle

Stress: when force is applied to an object

Compressive: a stress that squeezes an object and compacts it together

tensile: a stress that pulls an object apart

shearing stress: a stress that causes different parts of the object to move in different directions and slide past one another; like a deck of cards spreading out ovver a table top

Strain: deformation resulting from stress

elastic deformation: when this occurs the amount of deformation is porportional to the stress and the object returns to its normal size after the stres is removed

elastic limit: point at which elactic ability of the matrial has been surpassed and the material is permantetly deformed; this next stage is called plastic deformation

plastic deformation: stage of compression where a small stress added yields large corresponding strains, and the changes are permanent

rupture: if the stress is increased beyond plastic deformation, the material will break or rupture

brittle: in brittle materials rupture may occur before there is any plastic deformation

lithosphere: the outer crust of the earth, varies in thickness from 50km, 30miles to 100km, 60 miles 100 km (60 mi) on land, 50 km (30 mi) on ocean floor

athenosphere: layer immediately below the lithosphere, soft like putty, can move to some degree. is under high temp and moderate stress allows rocks to melt. that will not under higher pressure. avg 300 km. (200 mi)

africa and south america fit together along the continental shelf. where that rift occurred and in mant other palces on the ocean floor where spreading has occures there paralllel stripes of rock moving youngest to oldest from inside to out and also having reversing strips of magnetism.

Curie temperature: temperature above which a rock loses its magnetism due to the loss of order in its atomic structure. when it cools the atoms align anain according to the poles and are set until it melts again. this typically ocurs with ferromagnesium silicates and other iron bearing materials.

paleomagnetism: the study of fossil magnetisim. magnetic rocks have poles pointing towards the location of the north pole when they ae formed. this can be used to find the shift of the continents and the north pole. also it was discovered that the magnetic poles reveres every few million years.

sea floor spreading: the moving apart of the lithospheric plates at the ocean ridges. new basaltic rock is fromed at the ridges replacing land lost at the subducton zones. none of these rocks are over 200 million years old because the sea floor is constantly being subducted and destroyed.

polarwandrer curve: the curve that is a result of the apparent movement of the magnetic pole relative to the continent. it is really the continent that moved.

ancient plants and animals have been found of separate continents, and have been used as evidence that the earths continencs were once pushed together into a super continent 200 million years ago. examples of these animals include: Glossopteris and. mesosaurus both found in south america africa and india. and some in australia

Pangea: the name given to the super continent that is believed to have broken up 200 million years ago.

divergent plate boundary: place such as the ocean floor where the lithospheric plates are moving apart

transform fault: the connecting fracture that runs peipindicular to different parts of a major fault that are not exactly parallel and connaects them together. -------\______\------------

most famous is the San Andreas fault.

convergent plate boundary: a place where plates move together and collide. subduction usually happens here. the Himilayas were believed to be fromed by this.

subduction zone: a type of boundary where one plate is carried uner another

island arc (archapelligo): chain of islands created by volcanoes caused by convergence and sunduction of oceanic lithosphere

hot spots: isolated ares of volcanic activity not usually associated with plate boundaries. hawiian islands are an ex.

convection cells: theory of how the energy could be generated for plate techtonics to occur. scheme involves the circulation of hot and cooler material within the athenosphere that would force the plates to move. caused by uneven heat diffusion from the earth's core. possibly the result of radioactive deposits...

plates move an average of 2 to 3 centimeters per year.

suduction zones generate the largest earthquakes.

the Atlantic ocaen is expanding and the pacific is contracting.

erodogny: when rocks are forced up above the crust because they have beensquashed and deformed under stress

Evidence for plate techtonics

1 continental fit

2 similarity of rock sequences

3 global evidence

4 fossil evdience

5 polar wandering

6 sea floor spreading