Activity at plate boundaries

Type of plate boundary	Description of changes	Earthquake / volcanic activity	Examples
Constructive zone	Two crusts / plates move away from each other.	Moderate volcanic and earthquake activity.	Mid-Atlantic ridge. Iceland.
Destructive zone	Oceanic crust / plate moves towards continental crust / plate. The oceanic crust is heavier and sinks.	Violent volcanic and earthquake activity.	Nazca and South American plates.
Collision zone	Two continental crusts / plates collide and are forced up into fold mountains.	Earthquake activity, (no volcanic activity).	Indo-Australian and Eurasian plates.
Conservative zone	Two plates move sideways past each other.	Violent earthquake activity (no volcanic activity).	Pacific and North American plates. San Andreas, California.

Type of plate boundary	Drawing
Constructive zone
Destructive zone
Collision zone
Conservative zone

Plate tectonics

 Plate tectonics is a scientific theory describing how continents move around on the mantle and how sea floor is produced and destroyed. Plate tectonics is able to account for many major geological features: mountain building, volcanoes, earthquakes, the worldwide distribution of fossils and the ages of rocks on continents and the sea floor.

  

Plate tectonics

http://www.youtube.com/watch?v=ryrXAGY1dmE&feature=related

http://www.youtube.com/watch?v=6OHRb_ODo-Q&feature=related

http://www.youtube.com/watch?v=Bf4iJvrAv-M&feature=related

Plate tectonics is a scientific theory which describes the large scale motions of Earth's lithosphere. The theory builds on the older concepts of continental drift. The lithosphere (the shell of a rocky planet) is broken up into what are called tectonic plates. In the case of the Earth, there are currently seven or eight major and many minor plates. The lithospheric plates ride on the asthenosphere (the upper mantle just below the lithosphere). These plates move in relation to one another at one of three types of plate boundaries: convergent, or collisional boundaries; divergent boundaries, also called spreading centers; and conservative transform boundaries. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries. The movement of the plates varies, from 0 to 100 mm annually.

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