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Plate Tectonics
Our Dynamic Planet
Continental Drift
In 1912, a German scientist (he was an explorer,
astronomer, and meteorologist) proposed that at
one time all of the continents had been joined
together to form one huge continent
 His name was Alfred Wegener
 He called this supercontinent Pangaea (it means
“all Earth”)
 And, over time (millions of years), the continents
slowly drifted apart and ended up in the
positions we see on Earth today

Continental Drift
Continental Drift
Wegener could even provide 6 pieces of
evidence to support his claim
 1) Continents seem to fit together like
pieces of a jigsaw puzzle
 2) Fossils of the same organisms are
found on different continents
 3) Plant fossils (ferns) have been found
under Antarctic ice! (What’s so weird
about that??)

Continental Drift
4) Spotted cats are found in South America
(jaguars and ocelots) and Africa (panthers and
leopards)
 How did they get on 2 different continents – did
they swim across the Atlantic Ocean?
 Also Similar bird species found on 3 different
continents:
 Ostrich (Africa), Rhea (S. America), and Emu
(Australia)

Continental Drift
5) Veins of certain minerals appear to
begin in one continent and end in another
 For example, diamonds in Brazil and S.
Africa
 6) Mountain ranges in N. America and
Europe line up
 Also, scars from glaciation appear on
opposite continents

Continental Drift
Continental Drift – Matching
Mountain Ranges
Continental Drift – Glacier Evidence
Continental Drift
Wegener’s idea was ridiculed by geologists
 This is because while Wegener could provide
evidence, he couldn’t provide an actual
mechanism – an Earth PROCESS – that could
cause huge land masses to move across the
globe
 However, new technology finally led to findings
to support Wegener’s theory
 Ultimately a new theory was formed called
“Plate Tectonics”

What is Plate Tectonics?
Earth’s upper mantle and crust are
composed of solid, rigid rocks
 This uppermost region is called the
LITHOSPHERE
 The lithosphere is broken up into separate
sections called plates
 These plates (there are about 12) move
over the less rigid (more fluid) material of
the ASTHENOSPHERE (the lower mantle)
