In the 1960s, scientists developed a new theory that combined continental drift and sea floor spreading. According to this theory, the Earth is broken into irregularly shaped plates that move. The plates are made of the crust and a part of the upper mantle. These two parts combined make the lithosphere. The asthenosphere is a plastic-like layer below the lithosphere.
One scientist, J. Tuzo-Wilson, made an important contribution to the theory of plate tectonics. He came up with the idea that some volcanic island chains may have formed because of a "hotspot" in the mantle. He also came up with the idea that there must be a third type of plate boundary to connect the oceanic ridges and trenches.
> Plates move at different speeds and directions
> Most plate boundaries are on the ocean floor
> Oceanic plates are denser than continental plates
> Plates moving over each other is called subduction
> Three types of plate boundaries
One scientist, J. Tuzo-Wilson, made an important contribution to the theory of plate tectonics. He came up with the idea that some volcanic island chains may have formed because of a "hotspot" in the mantle. He also came up with the idea that there must be a third type of plate boundary to connect the oceanic ridges and trenches.
> Plates move at different speeds and directions
> Most plate boundaries are on the ocean floor
> Oceanic plates are denser than continental plates
> Plates moving over each other is called subduction
> Three types of plate boundaries
- Divergent Boundaries~ occur at mid-ocean ridges, the plates move apart, also called constructive boundaries
- Transform Boundaries~ move side by side, earthquakes often occur along strike-slip boundaries
- Convergent Boundaries~ plates come together, collision of plates at convergent boundaries cause lots of friction and pressure
- Ocean- Ocean~ plate being subducted melts
- Ocean- Continent
- Continent- Continent~ gets mountains when plates collide