The document summarizes Alfred Wegener's theory of continental drift from 1912. It proposed that the continents were once joined together in a supercontinent called Pangea, which later broke apart and drifted to their current positions. Wegener noted evidence supporting this, like matching fossil and rock formations across oceans, but did not know the mechanisms that caused the drift. Later studies discovered plate tectonics, including sea floor spreading at mid-ocean ridges, which provided the explanation for how and why the continents moved over time.

2. Proposed by Alfred
Wegener in 1912; the
hypothesis that state that
the continents once formed
a single landmass
(Pangea), broke up, and
drifted to their current
location

4. a) Shape of the continents
b) Fossil evidence on both
sides of the Atlantic
c) Rock formations on both
sides of the Atlantic
d) Climatic evidence (i.e.
evidence of glaciers in
Southern Africa)

6. He could not come up with
the mechanisms or process
that caused the continents
to move

7. a) Mid-Ocean Ridges – a
long undersea mountain
chain that has a steep,
narrow valley at its center,
that forms as magma rises
from the mantle, and that
creates new ocean floor as
the tectonic plates move
apart

8. b) Sea Floor Spreading –
the process by which new
oceanic crust forms as
magma rises to Earth’s
surface and solidifies at a
mid-ocean ridge, symmetry
of rock layers show oldest
layers are farther from the
ridge

9. c) Paleomagnetism –
• As magma solidifies, iron
particles line up with the
Earth’s magnetic field
• Rocks show reversals in
the Earth’s Magnetism
• Rocks show symmetrical
patterns on both side of the
ridges, thus both plates
formed at the same time

11. The theory that explains
how large pieces of the
crust, called plates, move
and change shape

12. Lithosphere – solid, outer
layer of the Earth that
consists of the crust and the
rigid upper part of the
mantle
Asthenosphere – the solid,
plastic layer of the mantle
that flows slowly

13. 15 Major Plates Identified:

14. Convection – the movement
of hot, less dense material
up and cold, more dense
material down

15. • Interior of the Earth heats
the mantle which rises to
the surface at the Mid-
Ocean Ridges
• Cools into rock and
eventually sinks back
into the mantle where it
is melted and sinks
• This movement of the
mantle drags the plates
with it

17. The boundary between
tectonic plates that are
moving away from each
other.
Results in: magma rises to
surface, forms mid-ocean
ridges and rift valleys

18. The boundary between
tectonic plates that are
moving towards each other

19. One plate subducts under
the other, forming a trench
and melting the plate
causing an island arc

20. The oceanic plate subducts
under the less dense
continental plate, the
oceanic plate melts, causing
volcanoes above

21. Neither plate is dense
enough to subduct, thus
mountains are built up

22. The boundary between two
tectonic plates that are
sliding past one another,
like the San Andreas fault