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
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
Click here (School Members only) for a further animation that shows the collision zone between
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
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.
The Soufriere Hills volcano on the island of Montserrat became active in 1995 and was the site of numerous explosive eruptions during the last few years. Collapse of the summit dome has generated numerous pyroclastic flows that have devastated the southern part of the island.
Click hereto see how the eruption of
Click hereto see how a few volcanoes, such as those on
Click here(External Link) to see how a caldera forms from a collapsed volcano, such as the
Click here(External Link) to see how a range of landforms result from intrusive and extrusive volcanic activity.
Click here to see how geysers are caused by super-heated water and steam escaping from the ground.
Click here(External Link) to see how the silicon content in magma can influennce the shape of the volcanic cone and the type of eruption.
A satellite image of Mount Vesuvius near Naples in southern Italy. The volcano is still active although no eruption is expected in the near future. It was the eruption of AD 79 which destroyed the Roman towns of Pompeii and Herculaneum. Further smaller eruptions occurred in 203, 472 and 1036. The last eruption was in 1500.
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 (External Link) to see a map showing the earthquakes that have occurred in the last hour, day and wek in
Click here to see how rocks which will not fold may crack or fault when subjected to tension or compression.
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.
|The San Andreas Fault|
The fault is not a straight boundary between the North American and Pacific plates. Along its southern section is a compression zone. This makes it difficult for the plates to pass each other so pressure builds up. The sudden release of pressure leads to violent and unpredictable earthquakes.
+ نوشته شده در جمعه 1386/04/29ساعت 8:53  توسط عباس دوکوهکی |
+ نوشته شده در جمعه 1386/04/29ساعت 8:24  توسط عباس دوکوهکی |
+ نوشته شده در جمعه 1386/04/29ساعت 8:6  توسط عباس دوکوهکی |
+ نوشته شده در پنجشنبه 1386/04/28ساعت 8:58  توسط عباس دوکوهکی |
Antique map of Persia by Tallis
|SIZE (hxw cms)||34.0 x 25.0|
|CONDITION||The overall quality of this antique map is excellent|
|DESCRIPTION||'Frequently referred to as 'the decorative series of world maps''. (Potter).|
+ نوشته شده در جمعه 1386/04/01ساعت 0:14  توسط عباس دوکوهکی |