alfred wegener 1912
who and when proposed the theory of continental drift
aall the continents where once connected as a super continent called.......but have scince drifted apart
puzzle peices (africa and south america)
alfred wegener thought the continents looked like........
fossils of plants and animals
diffrent continents had the same....... of .........and .......
south america and afica both have fossils of this fresh water and land animal, that could not swim that great distance.
a plant found on five diffrent continents, not possible for it to travle such distances.
glacial scraping patterns
rocks on different continents have the same.......... (west side of africa and east side of south america -neither can sustain glaciers now)
composition and age
rocks on different coast are similar in ............. (appalachian mountains same as those found in greenland and western europe)
alfred wegener could not explain how continents..........most scientist dismissed it.
earths rotation and gravitational force of sun and moon
alfred wegener thought these things caused the continents to move
had issues with his credibility because he was a weather man
figured out how continents move
the mid atlantic ridge
discovered by scientist using sonar to map ocean floor
proposed the theory of sea floor spreading
hot less dense material below the earths crust rises towards the earths surface at mid ocean ridge. then it flows sideways carrying the seafloor away from the ridge in both directions.
sea floor spreading thing
age of rocks surrounding the ridge (eosfs)
the youngest rocks are closest to the ridge and become older as you move away
magnetic clues (eosfs)
the.......feild of earth has reversed throughout history, those reversals are recorded in rocks surrounding the ridge.
the ridge runs throught the country so it is being split apart
plate tectonics theory
combines continental drift and seafloor spreading
earths crust is broken into sections called .......
plates move on a plastic like layer of the mantle called........
large sections of earths crust, both oceaninc and continental.
2 plates move apart
2 plates push together
2 plates slide past each other
within the mantle cause movement; hot magma rises and cools when it gets close to the crust, causing a current that causes the plate above it to move
occur at all plate boundaries but largest are at transform
produced by underwater earthquakes
produced at subduction zones (oceanic pushes under continental) produced at divergent bounderies under water
produced at convergent boundaries (2 continental plates push together and are forced upward)
deep sea trenches
formed when 2 oceanic plates converge and both are pushed back into the mantle
formed when 2 continental plates pull apart.
stretch of under water ridges caused by continually erupting volcanoes
what did scientist find by using echo signals along the ocean floor?
strong enough to move continents new crust formed dips back down into interior of the earth
describe seafloor spreading
if two collide one is pushed down and melts into magma. destroyed in deep sea trenches
if the sea floor is spreading and earth is not getting any bigger, where is crust being destroyed?
earths moveing crust or a peice of crust
what is it meant by a plate?
earth quakes. move with earths rotation
what causes plates to move?
the atlantic is growing-new crust is being formed at mid atlantic ridge. the pacific is shrinking-crust pushed back down into mantle. it melts in deep sea trenches and subduction zones.
which ocean is growing? which is sinking? explain why.