-large scale movement of tectonic plates

-shape & fit (continental shelves)

-similar shorelines

-distinctive rock and fossil groups found Africa & South America

-mountains identical rocks/glacial same age

(alfred wegener 1915)

proposed all continents were once part of large supercontinent PANGEA

-supercontinent that formed by collision of all the contintenal crust

-late Palezoic

-all continents connected

-fits of the continents=continental shells

-fossil eveidence=opp sides of ocean (same ones)

-rock types & structural similarites (matching mountains)=distinct rocks

-Glaciation evidence=covered southern continents (same age)

-Paleoclimate evidence=extream change in climate ->climate belts (similar climate)

-original evidence for continental drift was continental rocks

-technological advances in the 50's & 60's allowed investigation of the sea floor

-geophysic & paleomagnetism provided new data

-pangea began to break into modern plates

200 million years

-show direction of earths magnetic feild

-determining rock's latitude of origin 

-certain igneous and sedimentary rocks can preserve the Earths magnetic field at the time and place the rocks formed

(mid 1950-60)

-ancient

-past magnetism recorded in rocks

-records of magnetic field/alteration latitude record magetic dip angle

-magnetic minerals (Fe,Ni)

-seafloor spreading 

-The location magnetic poles at the time the rock formed

-magnetic inclination: indicating how far from the pt of rock formation the magnetic poles lay

-earths polarity (magnetic field was normal or reversed at time rock formation

1962- Harry Hess of Princeton University

 (hypothesized)

-topography of the seafloor could be explained if the seafloor moves sideways, away from oceanic ridges

-

Magnetic Anomialies

(geomagnetic reversals)

1963 Vine & Matthews

-Earths polarity, magnetic field has changed from normal to reversed many times

-rocks record polarity during formations

-earth surrounded by magnetic field

-strongest near poles

-magnetic field generated in liquid metal region of outer core

-outer core=extreamly hot and flows at rate of several km/yr large convection currents

-convecting metal creates electrical currents=magnetic field

-earths magnetic periodically reverses polarity

north magnetic pole=south pole

south magnetic pole=north pole

-dates of earth magnetic polarity changes were determined from lava flows

-recorded in ocean crust-naval submarine 

-magnetic strips in ocean crust near ridges record earths geomagnetic reversal

-magnetic anomalies help determine velocities

(1-20 cm/year)

-plume of upwelling material from depth reaches the surface

-global

-basaltic volcanism

- plates move across "fixed" spot

-forms a track of volcanic activiity

-cooling and subsidence of volcanoes=islands

-determined rate & direction of plate movenment

rate=age of volcano

direction=tred of island chain

-geologic deposits indicating past climates 

-extreme change in climate compared to present

-basins are divided by large ridge system

-ridge system continuous around entire globe

-central rift valley within the ridge

-wegner hypothesis correct principle, contain incorrect details

-all realms of science must be found

-few scienctist considered wegner ideas plausible and continued to search

-magnetic stripes

-relates processes and timing to plate tectonic mechanism

-seafloor older farther from ridge