Presented by Rana Faizan Saleem Roll.No (10)

 Volcanoes  Structure of a Volcano  Volcanism and its Types  Types of Volcanoes  Landforms from Lava  Landforms from Magma  Benefits of Volcanoes

Introduction: Word Volcano taken from: Roman god of fire, Vulcan What is a Volcano?  Volcano – a weak spot in the earth’s crust where molten material (magma), comes to the surface.

How do Volcanoes formed?  When rock from the mantle melts, moves to the surface through the crust, and releases pent-up gases, volcanoes erupt.  Extremely high temperature and pressure cause the rock to melt and become liquid rock or magma. When a large body of magma has formed, it rises through the denser rock layers toward Earth's surface.

 As magma rises toward the surface, the pressure decreases allowing the dissolved gases to separate out forming bubbles  These materials erupts: i. Lava:(Liquid) ii. Volcanic Ash:(The Solid) iii. Volcanic Bomb: (Like Ash but large)

 Magma: Molten mixture of rock-forming substances, gases, and water from the mantle.  Lava: When magma reaches the surface it is called Lava.  Magma Chamber: The pocket beneath a volcano where magma collects  Conduit Pipe: A long tube through which magma moves from the magma chamber to the Earth’s surface  Vent: An opening where magma and gas leave the volcano

 Crater: Mouth of a volcano - surrounds a volcanic vent.  Throat: Entrance of a volcano. The part of the conduit that ejects lava and volcanic ash.  Flank: The side of a Volcano  Lava flow: A lava flow is basically a stream of lava on the surface.  Summit: Highest point  Ash: Fragments of lava or rock smaller than 2 mm in size that are blasted into the air by volcanic explosions.  Ash Cloud: A cloud of ash formed by volcanic explosions.  Parasitic Cone: A small cone-shaped volcano formed by an accumulation of volcanic debris.

Volcanism: When hot molten magma escapes from the Earth’s core becoming cooler, and forming hard rocks, we refer to this process as volcanism. Volcanism takes place both above the surface of Earth, as well as beneath its surface.  Extrusive Volcanism When molten lava escapes the Earth and reaches the surface geologists say that it is extrusive volcanism.  Intrusive Volcanism When molten magma cools and hardens beneath the surface of the Earth, we say that it is intrusive volcanism.

 Active Volcano: An active volcano is a volcano that erupts regularly. about 1510 active volcanoes in the world. (Pacific Ring of Fire):- The ring of fire is a circle around the edges of the pacific ocean where half the worlds valcanoes are located.  Dormant Volcano: A dormant volcano is a volcano that is not erupting, but supposed to erupt again.  Extinct Volcano: An extinct volcano has not had an eruption and is not expected to erupt again.

Following types on Shape basis:  Sheild Volcano  Composite (or Stratovolcano)  Cinder Cones  Lava Dome

Sheild Volcano:  A bowl or sheild shaped Volcano in the middle with long-gentle slopes made by basaltic lava flows,called flood basalt.  Shield volcanoes created the Hawaiian Islands

Composite Volcano :  A composite volcano is built up from alternate layers of ash, high viscosity lava and rock debris.  It has steep sides because when it erupts it lava is thick and viscous meaning that it does not travel great distances and stays on the side of the volcano.

Cinder Cones:  Erupts violently  Cinder cones form around a volcanic vent. Lava explodes into the air and cools very quickly forming accumulating a ring of volcanic fragments.

Lava Dome:  A dome volcano is a round shaped mountain made of viscous lava.  The lava has a high silica content that prevents the lava from flowing very far from its vent.  Most domes are formed by dacite and rhyolite lavas.  Mount Myoko Japan is example.

 Lava Plateau: A lava plateau is a plateau formed by low-viscous lava through numerous vents, during quiet eruptions.  Caldera: The main volcano vent dries out and the top of the volcano collapses into it.  Volcanic Neck: A volcanic neck forms when the magma inside a volcano turns into rock and the outside of a volcano wears away, leaving the spiky-shaped rock magma

LAVA PLATEAU CALDERA

 Dike: Magma hardens in a vertical crack  Sill: Magma hardens in a horizontal crack  Batholith: A large deposit of magma that cools underground.

Benefits of volcanoes  Soils  Energy from heat  Rock (Pumice)  Gases for industry