Tectonics - evidence for theory of continental drift Flashcards
PALEOMAGNETISM
can be used to date the age of new tectonic crust.
1) lava cooling forms igneous rock, e.g. Basalt at Mid-Atlantic Ride
2) Igneous rocks contain particles of magnetite - strongly magnetic
3) as the lava cools, magnetite orientates itself with Earth’s magnetic field
we can tell when the rock was formed as tectonic plates are constantly moving, so directions of the north and south pole changes
EXAMPLE: orientation of magnetic minerals are very closely similar in EASTERN COAST OF SOUTH AMERICA and WESTERN COAST OF AFRICA
SEA FLOOR SPREADING
occurs at divergent plate boundaries under oceans - there is a symmetrical patterns of alternating polarity of rock on either side of the ridge
continuous input of magma forming a mid-ocean ridge e.g. the Mid Atlantic Ridge
on land, a rift valley forms
rock samples were found to be younger the closer they were samples to the Mid Atlantic Ridge
can now be imaged and calculated using satellites
EXAMPLE - AMERICA is moving 2.5cm / year away from the UK
BIOLOGICAL EVIDENCE
similar fossils found on different continents - evidence that regions were once very close or joined together
EXAMPLE - fossils fuels of Mosasaurs found in both SOUTH AMERICA and SOUTH AFRICA
unlikely the reptile could have developed in both places or that it migrated across the Atlantic
EXAMPLE -
INDIA and ANTARCTICA - fossilised remains of a plant have been located in only these two areas
GEOLOGICAL EVIDENCE
similar pattern or rock layers on different continents - evidence they were once close or joined together
EXAMPLE - evidence of late carboniferous glaciation deposits found in SOUTH AMERICA, ANTARCTICA and INDIA
formations of these deposits cannot be explained by their current positions, they must have been formed together, then moved
