Before Wegener’s theory, it was believed mountains formed because the Earth was cooling down, and in doing so contracted. It then formed wrinkles, or mountains, in the Earth's crust. Similar to this apple. However this is not true, because if the idea was correct, mountains would be spread evenly over the Earth's surface.
Wegener revealed that mountains are actually formed as the border of two drifting continents crash into each other causing one to fold in on its self. For example, the Himalayas were formed when India came into contact with Asia.
Plate Tectonics
The definition of plate tectonics is the movement of plates and the activity inside the earth.
The Earth is made up of four layers; inner core, outer core, mantle and crust
The crust and upper mantle are broken into large pieces called tectonic plates this sometimes forms continents.
Tectonic plates are huge areas of the Earth, which float on the upper mantle, that push and pull causing them to move apart. These plates are moving at a few cm per year, up to thousands of kilometres over millions of years.
Sometimes Earth can get pushed up or down when plates collide contributing to the rock cycle.
The force of two tectonic plates meeting makes the Earth’s crust unstable as they push against each other; ride under or over one another. This crashing can cause mountain ranges, earthquakes or volcanoes. Volcanoes are formed at boundaries, earthquakes occur when plates move suddenly.
Scientists and geologists are trying to find clues to predict earthquakes and volcanic eruption, like, strain underground or magma movement under volcanoes.
However, this only makes it more likely not certain, but just a little warning could save lives by alerting residents and authorities.
- No-one could provide a good explanation of how whole continents could move apart.
- Wegener was not a geologist - he trained as an astronomer and meteorologist.
- There were other, simpler, explanations for the same evidence.
- It was felt his idea was too big for the evidence at hand.
Evidence
- In the 1950’s the Mid-Atlantic ridge was investigated. Scientists found that magma (molten rock) rises up through the sea floor, solidifies and forms roughly symmetrical underwater mountains either side of the ridge. This process-called seafloor spreading- causes the ocean floor to spread at a speed varied from 1 to 9 cm per year.
- Iron particles in the magma align and set themselves with the Earth’s magnetic field. Every half million years the Earth’s field swaps direction and the rock on either side of the ridge has bands of ‘alternate magnetic polarity’.
- Fossils of very similar plants and animals have been found on opposite sides of the Atlantic Ocean. One explanation of this was that the continents were linked by ‘land bridges’ which had sunk or been covered by water as the Earth cooled
- There were matching layers of rocks and earthworms
- Coastlines of Africa and South America join together like a jigsaw
- Fossils are found deep underground or high up in mountains.
- Radio active decay in the mantle produces enough heat for convection currents.
In conclusion I believe continental drifting is true as there is too much evidence to support
If continental drifting wasn’t true what explanation could be given as to why continents fit together like a jigsaw or that fossils of the same animals are found on different sides of the Atlantic Ocean.
I agree with Alfred Wegener’s theory of Pangaea splitting apart and moving away, however I believe that it is due to the convection currents in the Earth’s upper mantle.
