N
Continental
Drift
“The earth is all what we have in common”
-Wendell Berry
W
E
S
Objectives:
Discuss the history behind the Theory of Continental Drift;
Describe the Continental Drift Theory; and
Enumerate and explain the evidence used to support the idea
of drifting continents
What is continental drift?
Theory that explains how continents shift
position on Earth's surface
ALFRED WEGENER
The originator of the theory of continental drift by
hypothesizing in 1912 that the continents are slowly drifting
around the Earth
According to Alfred Wegener
a single
supercontinent,
Pangaea, separated
into the current
continents and moved
across Earth’s surface
to their present
locations
.
According to Alfred Wegener
He published his work
through a book
entitled “The Origin of
Continents and
Oceans”
in 1915
.
But some scientists were
doubtful about his theory…
• Until the 1950s-60s, it was
still widely held that that
continents and ocean basins
had fixed geographic
positions. As such, scientists
were reluctant to believe
that continents
could drift.
Until in 1960s
OCEANOGRAPHY
The ocean floor was
characterized by deep
depressions called
trenches and a
network of ridges
that encircled the globe.
These topographic
data,
together with heat
flow measurements,
led to the emergence
of the Seafloor
Spreading
Hypothesis which
revived interest in
Alfred Wegener’s idea
of drifting continents.
What caused the
continents to drift away?
Today, we know that the
continents rest
on massive slabs of rock
called tectonic plates
and these plates are
always moving and
interacting to each other.
EVIDENCE
SUPPORTING
CONTINENTAL
DRIFT
1. The fit of the continents
2. Similarity in geologic
units and structures
3. Fossil match
4. Glacial and paleoclimate
evidence
The fit of the
continent
Similarity in
geologic
units and
structures
Fossil
Match
Glossopteris
flora
(seed fern)
had large seeds and grew only
in subpolar regions, but fossils
were widely distributed over
Australia, Africa, India and
South America (later on
discovered in
Antarctica)
Cynognathus
and
Lystrosaurus
land reptiles whose fossils
were found across South
America, Africa, India and
Antarctica.
Mesosaurus
a freshwater reptile (cannot
cross oceans) whose fossils
were found only in
black shales about 260
million years of age
(Permian) in South Africa and
Brazil.
END SLIDE
Thank you for listening.
Please prepare one-fourth sheet
of paper for a short quiz.
1- 6 True or False
1. Alfred Wegener proposed that a single supercontinent,
separated into the current continents and moved across Earth’s
surface to their present locations.
2. In the evidences supporting the continental drift, opponents of
Alfred Wegener concluded that there are no fossil match between
landmasses.
3. In 1915, Alfred Wegener published his works in a newspaper
about the origin of continents and oceans.
4. Pangaea came from an ancient Greek word meaning “first
land”
5. Seafloor spreading is a geologic process in which tectonic
plates—large slabs of Earth's lithosphere—split apart from
each other.
6. The ocean floor was characterized by deep depressions
called trenches and a network of ridges that encircled the
globe.
7- 10 ENUMERATE the 4 evidences supporting the continental
drift.