continental drift/parts of the earth

Continental Drift

• Continental Drift

  • Discovered by Wegener (Meteorologist)

    • Travelled by balloon to watch these changes in the arctic

    • Universal Rejection of theory (due to being a meteorologist not a geoscientist)

    • Wegener could not understand why the continents were moving

  • The continents used to be one, but they moved apart horizontally

  • Supercontinent: Pangea - formed when the Earth’s landmasses including present day continents were joined together

  • Evidence:

    • Jigsaw fit of the continents

      • Eg; coastlines of South America & Africa fit together. Same story with other coastlines

    • Fossil Correlation

      • Where the fossils remnants of a creature in the past are on coastlines of continents

      • Eg; ancient freshwater reptile fossils found only in two places, southern South America, Southern Africa. Due to being a freshwater animal, it could not swim thru the salty atlantic ocean. They could not have evolved in one location and then travelled to the other without changes.

      • Mostly found where jigsaw continents shown

    • Rock & mountain correlation

      • Eg; mountains of modern day northeastern U.S. same age and type of rock found in U.K. & Northern Scandinavia.

      • Theory: rocks formed at the same time in the same location, but the moving continents teared the rocks apart (later discovered as tectonic plates)

    • Paleoclimate data

      • Theory: By looking at the past climate of the earth, there are glacial striations (makings) which show direction of ice, which is different from the direction where the ice is presently. Therefore, the glacial structures must have moved.

      • Eg; Some glacial striations are going towards the equator (very hot) so Wegener concluded that in the past these locations had been closer to the poles (colder climate)

The Influence of the Theory of Plate Tectonics

• Theory of Plate Tectonics:

  • The Earth’s lithosphere is made up of tectonic plates which are constantly moving slowly but gradually.

  • 20 tectonic plates where continents rest on

  • When plates collide and move suddenly, energy is released as earthquakes

    • Why they occur in specific areas (around tectonic plate boundaries)

    • As molten rock rises from beneath surface, it hardens at spreading tectonic plates, recording orientation of earth’s magnetic field

  • Move a few cm per year

  • Continents will converge again in 250 million years - new supercontinent: PANGEA PROXIMA

• Influence on Continental Drift

  • Advances in tech (warfare) eg; seismometers & magnetometers allowed study of earth.

  • Seismometers

    • Used for nuclear testing ground shaking

    • Monitor ground shaking showed earthquakes in specific regions

  • Magnetometers

    • Used to detect submarines

    • Discovered magnetic variations near undersea ridges (flip flop of earth's magnetic field)

  • Observations support a new theory (PLATE TECTONICS) on wegener's idea

• Structure of the Earth

  • Clarified the layers of the earth

    • Eg; under the crust/lithosphere there is molten rock

      • Mantle

      • Asthenosphere

      • Convection currents in the mantle