CONTINENTAL DRIFT AND PLATE TECTONICS THEORY

1880-1930

birth year and death year of Wegener

Alfred Lothar Wegener

He hypothesized that all of the

modern-day continents had

previously been clumped

together in a supercontinent

Pangaea

(“all lands” or “all the Earth”

jigsaw puzzle

In the early 1900s, Alfred

Wegener observed that

the coastal areas of the

continents today

seemed to look like

__________ pieces

that fit each other.

CONTINENTAL DRIFT THEORY

explained how continents

shift position on Earth's

surface.

Alfred Wegener,

explained why

look-alike animal and plant

fossils, and similar rock

formations, are found on

different continents.

APPARENT FIT OF THE

CONTINENTS

• The coastlines of the continents

  appear to fit together like a

  pieces of puzzle.

• Wegener pointed to matching

  rock formations and similar

  fossils in Brazil and West Africa.

FOSSIL CORRELATION

EVIDENCE

• Identical fossils of plants and

  animals have been found in the

  rocks on either side of the ocean.

• Fossils of Mesosaurus, a freshwater

  reptile, have been found both in

  Brazil and western Africa.

ROCK AND MOUNTAIN

CORRELATION

• Identical rocks and mountain

  structures have been found on

  either side of the ocean.

• Mountain ranges with the same

  rock types, structures, and ages

  are now on opposite sides of the

  Atlantic Ocean.

PALEOCLIMATE DATA

EVIDENCE

• Glacial scratch evidence has been

  found in warm regions.

• Grooves and rock deposits left by

  ancient glaciers are found today on

  different continents very close to

  the equator.

Wegener could not explain the force

that was making the continents move.

WHY CONTINENTAL DRIFT THEORY REJECTED?

Theory of Plate

Tectonics

it is tectonic plates, rather than continents, which are

moving.

tectonic plates

According to theory of plate tectonics, Earth’s

crust is broken into roughly 20 sections

called ____ on which the

continents ride.

Tectonic plates

• are pieces of the lithosphere

able to move because the lithosphere is stronger and more dense than the rock below it.

asthenosphere.

These pieces float on a layer of partly

liquid rock called?

Power of convection

Currents of heat and thermal

expansion in the Earth's mantle,

he suggested, could force the

continents toward or away

from one another, creating new

ocean floor and building

mountain ranges.

ARTHUR HOLMES, around 1930

Who suggested a mechanism that can explain Alfred Wegener’s theory of continental drift and when?

CONVECTION

CURRENTS

causes the tectonic plates to

move several centimeters per year

relative to each other.

Convection currents

drive the movement

of Earth's rigid tectonic plates in the

planet's fluid molten mantle

1960

Evidence for continental movement was revealed, leading to the a

new version of Wegener’s theory, the theory of tectonic plates.

CONTINENTAL DRIFT THEORY

• It describes the drifting of Earth’s

continents on the ocean bed.

• There are continents on Earth which

have drifted on the ocean bed.

• The occurrence of similar plant and

animals species around the shores

of different continents.

PLATE TECTONICS THEORY

• It describes the features and

movement of Earth’s surface in the

present and in the past.

• Earth’s lithosphere is composed of

different plates and they began to

move a long time ago.

• The presence of seven continents and

small islands is proof for plate

tectonics theory.