Transcript Continental_DriftAMT

Continental Drift
 The
earth is composed of several
layers that go through several
changes that are driven by processes
within the earth. These processes
occur because of heat and density.
Albert Wegner
German Scientist that came up
with the hypothesis of
continental drift in 1912.
 He observed several maps and
came up with a question that he
proposed a hypothesis from.
 Take a look at the map and
discuss with your partner when
he may have questioned in
1912.

Map of the world
Use map on Page 240 with Pangaea Activity
Wegner’s Hypothesis
 He
hypothesized that there was once
one super continent
 250 million years ago
 The crumpling of crust created the
mountain ranges
Evidence
 Not
only did the continents look as if
they fit together, but there should be
some sort of fossil and rock evidence
that they once were connected.
 Explain how studying fossils and rock
formations on different continents
prove their was a super continent?
 Mesosaurus, Climate & Rock
Formations
Mid-Oceanic Ridges
Undersea mountain
ranges through the
center of which run
steep, narrow
valleys.
 Magma runs up
through the
lithosphere and out
of these ranges
into the ocean
floor.

Oceanic Floor Spreading
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The sediment is thinner the closer it
gets to the narrow valley the
magma comes out of
They dated the fossils that were
found near the oceanic ridges and
found out that the fossils are
younger the closer you got to the
ridge.
This could only suggest what?
The rocks in the ocean are younger
that the rocks found on the surface.
The surface rocks are 3.8 bya while
the ones under ground were never
older than 175 myo.
Harry Hess

1950’s he through
that the rift at the
top of the ridge
was where magma
rises to fill the
crack and as the
rock moves away
from the rift new
magma replaces
the empty spot.
Hess’ Hypothesis
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His hypothesis was
that if the seafloor
was moving it
might drive the
moving of the
continents too.
Convection
Currents & Pie Pan
activity
Paleomagnetism
Earth’s Polarity
 In the 1960’s paleomagnetism –the study of
the magnetic properties of rock would give the
final evidence of continental drift
 Paleomagnetism-study of the alignment of
magnetic minerals in rock as it is formed.
 As rocks form the iron-rich minerals within
them will align with the magnetic field of the
earth. This becomes permanent and may not
be today’s magnetic field
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Iron Filling
Scientists were able to
map the reversal of
magnetic fields on the
ocean floor and found
that each side of the
ridge mirrored the other
They were able to date
these rocks with ones on
land with similar
magnetic fields and
found that younger rock
was at the center and
older was farther away.
Did this support Hess’
Hypothesis?
Theory of Sea-floor Spreading
 Molten
rock from the rift valley’s
cools and hardens and then is carried
like a conveyer belt away so that
new rock can be formed on the
surface of the ocean.
 Long
after his death Wegener’s
Continental Drift theory was
accepted.