lecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptx

lecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptxlecturer 04 volcanos.pptx

1. Balochistan UET, Khuzdar.

2.  Volcano refer to the eruption of hot molten lava from below the surface of earth.  A volcano is a vent in the earth’s crust through which Lava, Steam, ashes etc. are expelled.

3. HOW ARE THEY FORMED ? When tectonic plates collide and go through the process of subduction, it sets the foundation for a volcano. The overlapping of the tectonic plates causes the magma to break through the crust, which is the cause of a volcanoes' birth. •

4. HOW ARE THEY FORMED ? • When temperature and pressure rises, the rock melts and moves through the surface and crust, and releases gases and magma, volcanic eruption occurs.

5.  The narrow opening of a volcano is called Vent . The upper part of vent is a cup shaped depression called Crater .  The rock material ejected during volcanic activity is deposited on surface of Earth. It is called Lava.

6.  Pyroclastic Flow is fluidized mixture of solid to semi-solid fragments.  It is characterized by hot expanding gases that flows down the flank of volcanic edifice.

7. • Pyroclastic flows are mixtures of hot gas, ash and other volcanic rocks travelling very quickly down the slopes of volcanoes. They are one of the most dangerous hazards posed by volcanoes.

8.  Viscosity - the property of a fluid that resists the force tending to cause the fluid to flow  Magma - molten material beneath or within the earth's crust, from which igneous rock is formed  Lava - the molten, fluid rock that issues from a volcano or volcanic vent  Ash - the powdery residue of matter that remains after burning  Caldera - A large crater formed by volcanic explosion or by collapse of a volcanic cone. DEFINITIONS

9. There are three major types of volcanoes:  Shield volcanoes  Composite volcanoes  Cinder cone volcanoes

10. SHIELD VOLCANOES The magma inside a shield volcano is rich in iron and magnesium and is very fluid. Since the magma is very fluid, the lava coming out of the volcano tends to flow great distances. When shield volcanoes erupt, the flowing lava gives the volcano the shape of a gently sloping mountain.

11. COMPOSITE VOLCANOES The magma inside a composite volcano is rich in silica and much thicker than magma from a shield volcano. Gases get trapped inside this thicker magma. Eruptions from composite volcanoes can be flowing lava or explosions. The explosive eruptions come from the trapped gases and produce cinders and ash.

12. CINDER CONE VOLCANOES The magma inside a cinder cone volcano has large amounts of gas trapped in it. Eruptions from cinder cone volcanoes are violent and explosive because of all the gas trapped in the magma. The large amounts of hot ash and lava thrown out of the vent fall to the ground forming the cone shape that these volcanoes have .

13. CAUSES OF VOLCANIC ACTIVITY When a part of the earth's upper mantle or lower crust melts, magma forms. A volcano is essentially an opening or a vent through which this magma and the dissolved gases it contains are discharged.

14. EFFECTS OF VOLCANIC ERUPTIONS The effects of volcanic eruptions can be divided into primary and secondary effects. The primary effects are immediate and come from the eruption itself. The secondary effects result from the primary effects.

15.  Volcanic gases : All magma contains dissolved gases. These gases are mainly steam, carbon dioxide and compounds of sulphur and chlorine.  Lava flows : These are streams of molten rock.  Pyroclastic flows - These are high speed avalanches of hot ash, rock fragments and gas which move down the sides of a volcano. These flows occur when the vent area or ash column collapses.

16.  Lahars - These are mixtures of water, rock, ash, sand and mud that originate from the slopes of a volcano. Lahars often happen because of heavy rainfall eroding volcanic deposits.

17. Other secondary effects include:  Food / water supply interrupted.  Homelessness.  Businesses forced to close.  Cost of insurance claims.  Unemployment.  Long-term issues with the tourism industry.

18. Conclusion Volcanoes are caused when molten rock (magma) flows out onto the earth’s surface through fissures that are caused due to the movement of plates Though volcanic eruptions are threats to human life, the areas where the eruptions have taken place are useful too as t hese areas are rich in minerals. Volcanic Eruption cause heavy damage to human life and property.