1. volcanoes Engr. Imran Mehmood Civil Engineering Department
Swedish College of Engineering & Technology, Wah Cantt
Date # 29th Feb., 2012

2. VOLCANOES
“Volcanoes are the vents through which hot materials are discharged continuously or occasionally.”
“A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface.”
VOLCAN – ROMAN WORD MEANS GOD OF FIRE
These vents connect the surface of earth with the molten material inside the earth.”

3. Formation of volcanoes
Igneous Rocks
RECALL
Formation of volcanoes
Temperature increases with the depth
Temperature gradient 1˚C with 40 meters depth
At temperature above 1100˚C, all the rocks are in molten state, called MAGMA
Change in temperature or pressure take place
Magma, no longer remains in its original state
& moves towards the earth surface to erupt through the points of least resistance
“Volcanoes are formed, when the magma is forced out to escape or attempts to escape on the earth’s surface”

4. CAUSES OF Volcanoes The volcanoes may be caused due to:
Percolating Water – The water percolating through earth’s surface comes in contact with the molten rocks, changes to steam which results in creating enormous pressure and allows the molten rocks to move upwards through the path of percolated water (points of least resistance).
Most of the volcanoes of the world are situated near the sea.
Also volcanic eruptions are accompanied by some quantity of steam.

5. Products of eruption High Silica → More Viscous
Low Silica → Less Viscous
Lava
Cinders
Ash
Gases
Fined grained material mm to Several cm
Volcanic dust or particles < 5mm
CO2, SO2,H2S,HCL etc

6. Volcanoes around the world

7. Eruption style Lava flow Lava fountain Non-Explosive Eruption

8. TYPES OF eruptions Central Eruption Fissure Eruption
Magma Comes out from one location
Fissure Eruption
Magma Comes out from many locations

9. Classification (record of activity)
Active – Always active, stops for few periods of time and again starts
Dormant – Once erupts, then stops its activity for a considerable period of time, but the chances of eruption are there.
Extinct – which is quite ancient and have stopped it activity.
Active Volcano
Mount Aso - Japan
Dormant Volcano
Mount Price - Canada
Extinct Volcano
Monte Vulture - Italy