Why does crustal plates move

The bottom of the Atlantic Ocean is filled with some of the "youngest" crust on Earth. The island of Iceland, located in the North Atlantic, is still being formed at this Mid-Atlantic ridge. The Pacific Ocean, on the other hand, is becoming smaller and smaller. The North and South American plates are crashing into the thinner and denser oceanic plates of the Pacific. This drives the oceanic plates deep into the mantle destroying the oceanic plates.

This boundary in which an oceanic plate is driven down and destroyed by a continental plate is called a subduction zone. This Pacific Ocean region has more earthquakes and volcanic activity than any other area of the world.

Because of all the volcanoes this region has been given the nickname of "The Ring of Fire". When the less dense, lighter continental plate overrides the oceanic plate a subduction zone forms. Because the oceanic plate is bent and driven down, a deep trench forms at this collison point. These trenches are the lowest points on the Earth's crust. One trench is a mile deeper than Mount Everest is tall! As the oceanic plate descends into the mantle some of it melts.

This material moves into the mantle above the plate and causes the mantle to melt. This liquid rock, called magma, rises to the surface because it is less dense then the surrounding rock. If the magma reaches the surface of the Earth, a volcano forms. As the mantle rocks melt they form magma. Why can't S-waves travel through liquids? How far can seismic waves reach? Why do P-waves travel faster than S-waves? Why is the interior of the Earth hot?

What is the magnetic field of the Earth? Earthquakes and Faults Why do tectonic plates move? Brief history of the plate tectonics theory Before colliding with Asia, where was India? What is an earthquake? What is the highest magnitude an earthquake can reach? What are the biggest historical earthquakes? Why do earthquakes happen in clusters? Where are earthquakes expected in the world, especially in Asia?

What is a supercontinent? Are all the faults on Earth active? How can human activities cause climate change? Why do urbanisation and deforestation make flooding more likely? Earthquake Hazards Is Singapore threatened by earthquakes? This position makes New Zealand geologically active with frequent earthquakes, geothermal areas and volcanoes.

This plate boundary has shaped New Zealand:. Watch the GNS Science animation k , showing the future shape and deformation of New Zealand if the movement measured between were to continue unchanged.

Iceland sits on top of the Atlantic ridge, the divergent boundary between the Eurasian and North American tectonic plates: As the two plates drift in opposite directions Iceland is in effect slowly being split apart.

This plate movement makes Iceland geologically active, just like New Zealand. Ready for a quiz? Try 'The Moving Crust' interactive activity. Try this Pangaea to Present activity. Convection currents caused by heating in the Earth's mantle explain how the continents move. Who came up with this theory and what is this theory called?

Image: Public Domain. How do you think this affects New Zealand? Image: USGS. The hot water moves to the surface, then spreads out and cools. Cooler water sinks to the bottom. Magma is the molten rock below the crust, in the mantle. Tremendous heat and pressure within the earth cause the hot magma to flow in convection currents.

Based on evidence that has been found at plate boundaries, make some hypotheses about the movement of those plates. The earth has changed in many ways since it first formed 4. They have gradually moved over the course of hundreds of millions of years—alternately combining into supercontinents and pulling apart in a process known as continental drift.

The supercontinent of Pangaea formed as the landmasses gradually combined roughly between and mya. It is widely accepted by scientists today. Earthquakes and volcanoes are the short-term results of this tectonic movement. The long-term result of plate tectonics is the movement of entire continents over millions of years Fig. The presence of the same type of fossils on continents that are now widely separated is evidence that continents have moved over geological history.

Evaluate and interpret several lines of evidence for continental drift over geological time scales. The shapes of the continents provide clues about the past movement of the continents.

The edges of the continents on the map seem to fit together like a jigsaw puzzle. For example, on the west coast of Africa, there is an indentation into which the bulge along the east coast of South America fits. The shapes of the continental shelves—the submerged landmass around continents—shows that the fit between continents is even more striking Fig. Some fossils provide evidence that continents were once located nearer to one another than they are today. Fossils of a marine reptile called Mesosaurus Fig.

Another example is the fossil plant called Glossopteris, which is found in India, Australia, and Antarctica Fig. The presence of identical fossils in continents that are now widely separated is one of the main pieces of evidence that led to the initial idea that the continents had moved over geological history. Evidence for continental drift is also found in the types of rocks on continents.

There are belts of rock in Africa and South America that match when the ends of the continents are joined. Mountains of comparable age and structure are found in the northeastern part of North America Appalachian Mountains and across the British Isles into Norway Caledonian Mountains. These landmasses can be reassembled so that the mountains form a continuous chain.

Evidence from glacial striations in rocks, the deep grooves in the land left by the movement of glaciers, shows that mya there were large sheets of ice covering parts of South America, Africa, India, and Australia. These striations indicate that the direction of glacial movement in Africa was toward the Atlantic ocean basin and in South America was from the Atlantic ocean basin.

This evidence suggests that South America and Africa were once connected, and that glaciers moved across Africa and South America. There is no glacial evidence for continental movement in North America, because there was no ice covering the continent million years ago.