Theories of the Earth’s Crustal Movement

CONTINENTAL DRIFT CONTINENTAL DRIFT THEORYTHEORY

In 1915, the German geologist and

meteorologist Alfred Wegener first proposed the theory of continental drift, which states that parts of the Earth's crust slowly drift atop a liquid core. The fossil record supports and gives credence to the theories of continental drift and plate tectonics.

Wegener hypothesized that there was a gigantic Wegener hypothesized that there was a gigantic supercontinent 200 million years ago, which he named supercontinent 200 million years ago, which he named

Pangaea, meaning "All-earth"., meaning "All-earth".

Pangaea started to break up into two smaller supercontinents, called Laurasia and Pangaea started to break up into two smaller supercontinents, called Laurasia and Gondwanaland, during the Jurassic period. By the end of the Cretaceous period, the Gondwanaland, during the Jurassic period. By the end of the Cretaceous period, the continents were separating into land masses that look like our modern-day continents were separating into land masses that look like our modern-day continents.continents.

seafloor spreading, theory of lithospheric seafloor spreading, theory of lithospheric evolution that holds that the ocean floors are evolution that holds that the ocean floors are spreading outward from vast underwater spreading outward from vast underwater ridges. First proposed in the early 1960s by the ridges. First proposed in the early 1960s by the American geologist Harry H. Hess, its major American geologist Harry H. Hess, its major tenets gave great support to the theory of tenets gave great support to the theory of continental drift geological theory that the geological theory that the relative positions of the continents on the relative positions of the continents on the earth's surface have changed considerably earth's surface have changed considerably

through geologic timethrough geologic time..

Plate tectonics is the theory that the outer rigid layer of the Plate tectonics is the theory that the outer rigid layer of the earth (the earth (the lithospherelithosphere) is divided into a couple of dozen ) is divided into a couple of dozen "plates" that move around across the earth's surface relative "plates" that move around across the earth's surface relative to each other, like slabs of ice on a lake.to each other, like slabs of ice on a lake.

Brainstorming Activity:Brainstorming Activity:

Of the three theories Of the three theories presented, which one presented, which one convinced you most?convinced you most?

THANK YOU AND HAVE A GOOD DAY!

By: Beth G. LabradorJimalalud National High School Jimalalud, Negros Oriental