The Question of Plate Tectonics
Calab Holder
Welcome to the premier, most comprehensive source of information on the internet on the subject of plate tectonics...probably
Continental Drift Overview
Three compelling pieces of evidence in defense of Wegener's theory.
Plant Fossils
Fossils of the same plant Glossopetris were found on different continents. This may suggest that the continents were once joined.
Freshwater Fossils
Fossils of the reptile Mesosaurus have been found on separate continents. Since Mesosaurus was a freshwater animal, it may not have been able to brave the rough journey across the Atlantic's ocean water.
Climate Clues
Warm-weather fossils were discovered on the island of Spitsbergen in the Arctic Ocean. Since Spitsbergen is located in a cold-weather climate currently, this may mean that all continents were joined together with the same climate.
Continental Drift Statement
Harry Hess's theory of Seafloor Spreading.
Seafloor Spreading Overview
Subduction zones
The subduction zone is the area where the oceanic crust slips beneath the continental crust and re-melts where is shoots up through volcanoes.
Older/Newer rocks
When you are closer to the mid-ocean ridges the rocks are newer as that's where new rocks form. As you get further from the mid-ocean ridges you encounter rocks of older origin.
Magnetic polar reversals
When you move further away from the mid-ocean ridges, there are magnetic polar reversals in the rock as the Earth's magnetic field flips and changes.
Seafloor Spreading Statement
Plate Tectonics
Plate Tectonics Overview
The Earth's Plates
Scientists think that the Earth's plates float on a a plastic-like layer called the astenosphere. Along these plates are places called boundaries.
Different types of plate boundaries
Divergent boundaries move apart from each other. These types of boundaries cause rift valleys. Convergent boundaries move together and form mountains/volcanoes. Transform boundaries slide against each other. These types of boundaries cause earthquakes.
Convection currents
Some scientists believe that currents of heat that originate from deep within the Earth cause the Earth's plates to move. These currents of heat are called convection currents