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Thursday, March 20, 2014

Volcanic Landforms and Processes

Whats the different between volcanism and volcanoes?

Fig. 1

Volcanism is the process by which magma and associated gases rise onto the Earth's crust and are extruded on the earth's surface or in the atmosphere. And Volcanoes is the surface manifestations of volcanism. Global pattern of volcanism are related to plate boundaries (active seismic regions)(Fig 1). The type of volcanic activity depemds mainly on the type of plate boundary. The shape and dimensions of a volcano depend mainly on the eruption type. (see the image below)

Fig. 2
On the diverging plate margins, volcano has quiet eruptions of basaltic magma, on the converging plate margins (subductions) volcano has an explosive eruptions of andesitic magma, and on the interplate (hot spot) volcano has an eruptions of basaltic magma (Fig 2).

Fig. 3

Eruptions range from quiet outflows of lava to very explosive eruptions. This depends on viscosity ang gas content of the magma. This viscosity depends on chemical composition, pressure and temperature. The type of eruptions are : vesuvian type, pelean type, plinian type, vulcanian type, strombolian type, hawaiian type, fissure type.

These picture are some example of famous volcanoes in the world :
1. Vesuvius, Italy

2. Cindercone, Mexico

3. Tengger (Bromo), Indonesia.

4. Cindercone and example of subsidence, Ijen, Indonesia

5. Large crater in the summit, Raung, Indonesia
6. Small caldeira with new cone, Rindjani, Indonesia

7. Caldera with younger cones, Ijen complex, Indonesia
8. Lava flow, Hawaiian type
9. Lahar, Merapi, Indonesia
10. Kelud, Indonesia
11. Eroded volcanoes, Philiphines
13. Volcanic necks, Camerun

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