1 Plate Tectonics, Theories Flashcards
4 theories
RAISIN THEORY
THEORY OF ISOSTASY
THEORY OF TECTONIC
CONTINENTAL DRIFT THEORY
(CONTRACTING EARTH THEORY)
contracted due
to cooling process;
RAISIN THEORY
(raisin theory)
________ – caused the
contraction
________– parts of the crust
move upwards (mountain)
and buckled downwards
(ocean basins and
depressions)
cooling
pressure
equilibrium
between the Earth’s crust
and its upper mantle,
lighter crust must be
floating on the denser
underlying mantle.
THEORY OF ISOSTASY
(ISOSTASY)
➔The term was first
proposed by, ______________an American
geologist in 1889.
CLARENCE
DUTTON
Greek ____ “equal”, _____ “standstill”
isos
stasis
Greek isos “_____”, stasis “_______”
equal
stanstill
THREE THEORIES THAT EXPLAINS THE CONCEPT OF ISOSTASY.
AIRY’S THEORY
PRATT’S THEORY
HEISKANEN’S THEORY
AIRY’S THEORY
Proponent:
Sir George Biddell Airy
He assumed that the density of the
crust is the same throughout.
Because the crust is not uniformly
thick, the thicker parts of the crust
sink down into the mantle while the
thinner parts float in it.
AIRY’S THEORY
PRATT’S THEORY
Proponent:
John Henry Pratt
There are lateral changes in rock
density across the lithosphere.
He assumed that the mantle
below is uniformly dense, the less
dense crustal block float higher
to become mountains.
PRATT’S THEORY
HEISKANEN’S THEORY
Proponent:
Weikko Aleksanteri
He accepted the “root theory” of
Airy, but he also showed that the
density may vary horizontally
from column to column.
HEISKANEN’S THEORY
Formation and structure
of the earth’s crust.
The theory states that the
Earth’s solid crust, the
lithosphere, is separated
into plates that move
over the asthenosphere.
THEORY OF TECTONIC
