tectonics.

Click here to view an animation showing how rift valleys develop into constructive plate margins leading to the development of new oceans. The Atlantic formed in this way about 200 to 250 million years ago.

Click here to see how plate tectonics provides the explanation for continental drift and the break-up of the super-continent of Pangaea about 225 million years ago. Click here (School Members only)  for an alternative animation.
 

Click here to see an animation showing the convectional currents in the mantle which drive surface crustal plate movements.

Click here (School Members only)  to see how constructive and destructive plate margins work together in the rock cycle.

Click here to see the formation of earthquake and volcanic activity at constructive plate boundaries.

Click here to see how the magnetic field of the earth reverses and how the pattern is recorded in the igneous rocks that are formed on either side of a mid-ocean ridge at a constructive plate margin.

Click here to see how basaltic lava enters the cold sea water at ocean ridges adding fresh rock to each crustal plate.

Click here to find out how oceanic crust is destroyed at destructive plate margins. These are also locations where there are ocean trenches, fold mountain ranges, volcanic activity and earthquake activity.

Click here to see how andesitic (or acidic) magma is created in a subduction zone which feeds intrusive and extrusive volcanic features.

Click here to find out how island arcs, such as the Aleutian Islands or the Japanese islands, form where a subduction zone forms between two oceanic crustal plates.

Click here to see how collision zones occur when two continents meet at a destructive plate margin, leading to major mountain ranges such as the Himalayas. The animation is in the form of a cross-section.

Click here (School Members only) for a further animation that shows the collision zone between India and Asia from a plan (map) view.

Click here (School Members only) to see how "foliated" metamorphic rocks can be formed at collision zones as a result of the intense pressure and heat.

Click here (School Members only)  to see how transform faults form, such as those in California, Turkey or offset from the Mid-Atlantic Ridge. The animation includes maps of example locations.

Click here to see the creation of rock at constructive plate boundaries, and how the destruction of rock at subduction zones helps to complete the rock cycle.

Volcanic Features

Click hereto see how the eruption of Mount St. Helens was triggered by a massive landslide, which itself was set off by earthquakes and the unstable, bulging cone of the volcano.

Click hereto see how a few volcanoes, such as those on Hawaii, are formed over magma plumes or hot spots, rather than close to plate margins. As the Pacific plate moves north westwards, the older, extinct volcanoes form coral reefs and then eventually subside and erode back beneath the sea.

Click here(External Link) to see how a caldera forms from a collapsed volcano, such as the Crater Lake in the USA.

Click here(External Link) to see how a range of landforms result from intrusive and extrusive volcanic activity.

Earthquakes and Earth Movements

Click here to see how seismic waves, generated by earthquakes, exist in a number of different forms including primary (push)waves, secondary (sine) waves, longwaves (love waves) and Rayleigh waves. Click here (External Link) for an alternative animation.

Click here to see how seismographs of different kinds are used to measure and record earthquakes. Click here (External Link) for an alternative animation.

Click here (External Link) to see a map showing the earthquakes that have occurred in the last hour, day and wek in California and Nevada.

Click here to see how plate movements cause soft sedimentary rocks to fold in a number of different ways. Click here (External Link) for an alternative animation showing horizontal and plunging folds.

Click here to see how rocks which will not fold may crack or fault when subjected to tension or compression.

 Click here to see how earthquakes can set off landslides and other types of mass movement.

Click here to see how earthquakes can set off tsunamis such as the Indian Ocean Tsunami on 26 December 2004.
 

As Geographers we are just as interested in solutions as we are in causes. Visit the New Bay Bridge (External Link) website where you can find out how the old bridge was damaged in the 1989 earthquake and test out your own online designs for the new bidge. You can also see the actual design and the stages in the construction of the real bridge.