3.1.5.2 Plate Tectonics Flashcards
who was first to notice the jigsaw fit on SA and west africa and when
francis bacon
early 17th century
who published the theory of pangea and when
alfred wegener in 1912
what two continents did pangea split into
Laurasia
Gondwanaland
what evidence is there of pangea
similar rock types and fossils in africa and south america
jigsaw fit
magnetic field pattern in rocks containing iron
explain the evidence of the alternating magnetic field pattern in rocks
the reversal of the earths magnetic field meant that new rock at constructive margins would match that of the magnetic field
symmetry around the margin is evidence that the rocks are moving apart
which scientist developed the theory ofthe magnetic field pattern in rocks and when
Ewing
1948
characteristics of continental crust
up to 70km thick
+1500 million years old
mainly composed of granite, silicone, aluminium and oxygen
characteristics of oceanic crust
up to 10km thick
less than 200 million years old
mainly composed of basalt, silicon, magnesium and oxygen
what do plates float on
semi rigid asthenosphere
what are convection currents caused by
hot material in the deepest part of the mantle rising then cooling and sinking again
what is slab pull
the effect of gravity sinking the edge of an oceanic plate into the asthenospher and forms a trench
what is ridge push
plates pulling apart so magma rises where it cools and solidifies
what is paloemagnetism
the word used to describe sea floor spreading with the evidence of iron particles aligned in the worlds magnetic field
what is a divergent/constructive plate margin
crusts move apart to form new crust when magma rises in the gap
what is a convergent/destructive/subductive plate margin
when one plate moves under another