Expedition Earth

Thursday, 13 October 2011

How earthquakes work

http://www.youtube.com/watch?v=-zNyVPsj8zc&feature=related

Earthquake facts and a number of details about how Earthquakes work and form.

An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. Earthquakes are measured using observations from seismometers. Most earthquakes are measured mostly on the local magnitude scale, also referred to as the Richter scale. Magnitude 3 or lower earthquakes are mostly almost imperceptible and magnitude 7 and over potentially cause serious damage over large areas, depending on their depth. The largest earthquakes in historic times have been of magnitude slightly over 9, although there is no limit to the possible magnitude. The most recent large earthquake of magnitude 9.0 or larger was a 9.0 magnitude earthquake in Japan in 2011 (11-03-2011), and it was the largest Japanese earthquake since records began.

The formation of volcanoes explained in geological terms

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

The computer graphics shows Iceland on the mid-Atlantic ridge, a great fault lying between the Americas and Africa. The Earth's surface is divided into plates. The plates move across the Earth’s surface causing continental drift.

The animation shows a cross-section of the Earth, each layer is described and named, the theory of plate tectonics is introduced. An animation demonstrates the constructive and destructive elements of plate tectonics and how volcanoes are formed along plate boundaries. The video shows how 'hot spot' shape volcanoes on the Pacific plate. Mount Kilauea, Hawaii is a magnificent example of the most active volcanoes on the planet.

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.