Volcanoes and seismic activity, our latest simulations http://www.edumedia-sciences.com/ eduMedia, RSS feeds en quentin.thiaucourt@edumedia-sciences.com http://www.edumedia-sciences.com/media/logo.jpg Logo http://www.edumedia-sciences.com/ <![CDATA[Volcano diagram]]>

There are two kinds of volcanoes: one kind with violent eruptions producing steep slopes and the other kind with voluminous lava flows producing gentle slopes

The character of volcanic eruptions are largely controlled by the viscosity of the magma. Indeed, low -viscosity magma:

  1. flow more easily than high viscosity magma
  2. allow gases to escape easily whereas gas pressures can build up in high viscosity magmas.

Those two reasons explain why stratovolcanoes result in violent eruptions.

]]> <![CDATA[Volcanism]]>

There are more than 1500 active volcanoes on Earth. 95% of these are located at the boundaries of two plates (zones of divergence or of subduction) . The remaining 5% are located  above thermal plumes, in those regions known as “hot spots”.
It is estimated that 80% of these volcanoes lie under the oceans, located along the length of the oceanic ridges. They are at the origin of the material that makes up the ocean floor.
This volcanic activity is one of the numerous phenomena supporting the theory of Plate Tectonics. The gases, ashes and rocks expelled in eruptions are carefully studied in order to better understand the internal composition of the Earth.
Note:  These animations are not necessarily drawn to scale.

]]> <![CDATA[Earth's surface dynamics]]>

The Earth’s surface changes. A simplifed global view illustrate the dynamics of Earth’s interior. Some scale ratios are not respected.

]]> <![CDATA[Hot spot volcanism]]>

The Hawaiian islands formed successively over a common source of magma called a hot spot.

]]> <![CDATA[Tsunami]]>
The term ‘tsunami’ (harbour wave) comes from Japan where the phenomenon frequently occurs. When an underwater quake or any other cause suddenly sets a great depth of water into motion, it causes a gigantic wave to form. In the open sea, the undulation cannot be seen. However, when it hits shore, its height increases, submerging the coastline and destroying everything it encounters.

The main events preceding the Tsunami are illustrated here:
  • undersea earthquake.
  • propagation of the wave.
  • arrival on coasts.
]]> <![CDATA[Continental drift]]>
The heat from inside the Earth causes the material of the mantle to permanently rise up along the ocean ridges, resulting in the formation of a dense basaltic crust which slowly rolls away from the ridge, much like a rug being rolled up. The continents, which are made of an insubmergible lightweight crust, passively drift with the movement of the lithospheric plates on which they sit.
The animation illustrates the movements of the lithospheric plates from 250 million years in the past through to the present, as well as projections of continental movements 30 million years into the future.

]]> <![CDATA[Different types of faults]]>

Three types of fault movements (normal, reverse and strike-slip faults) are illustrated,  along with their locations  on a lithospheric plates boundaries map.

]]> <![CDATA[Speed of seismic waves]]>

Required time for seismic waves P, S and L to travel from the epicenter to three different seismometers placed at different distances.

]]> <![CDATA[December 26 2004 Tsunami]]>

Illustration of the tsunami’s progression, starting from the earthquake’s epicentre, on a map of the Indian Ocean.

]]> <![CDATA[Lithospheric plates]]>
Different types of observations related to lithospheric plates:
  • locations of plates.
  • topography.
  • age of the ocean floor.
  • locations of recent seismic activity and active volcanism.
  • geothermic waves emerging from the Earth.
    • ]]>