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)