VolcanoVolcanoBy: Carol and Thuthao

Why I Chose The TopicWhy I Chose The Topic

• I chose the topic because I wanted to explore the world of volcanic activities and see our surroundings.

• In addition of its surroundings, I also wanted to learned how a volcanic eruption happens.

Key StatementKey Statement• This presentation includes

the various types of volcanoes.

• The presentation also includes how the volcanoes look like and what their surroundings contain.

• In the following presentation you will also encounter different ways of how a volcano erupts.

Examples• Cinder Cone Volcano - built from

particles and blobs of congealed lava ejected from a single vent.

• Composite Volcano – have a crater at the summit which contains a central vent or a clustered group of vents.

• Shield Volcano - flow after flow pours out in all directions from a central summit vent, or group of vents

• Lava Domes - formed by relatively small, bulbous masses of lava too viscous to flow any great distance.

Cinder ConesCinder Cones• Cinder cones are the

simplest type of volcano. Cinder cones are chiefly formed by Strombolian eruptions. Cinder cones can only occur alone or in small to large groups or fields. The longer the eruption takes place, the higher the cone. If gas pressure drops, the final stage cinder cone construction may be a lava flow that breaks through the base of the cone. 2006 Brooks/Cole-Thomson

Composite VolcanoesComposite Volcanoes• Composites volcanoes are made

of layers of lava, ash, cinders, and bombs. Composite volcanoes are tall, evenly shaped, with steep sides, sometimes as high as 10,000 feet. Composite volcanoes comprise the largest percentage (60%) of the Earth’s individual volcanoes. Some composite volcanoes are just a collection of domes piled up on each other.

2006 Brooks/Cole-Thomson

Shield VolcanoesShield Volcanoes• Shield volcano is made of

thin pahoehoe lava from quiet eruptions hardening on layers of lava over and over again. Lava tubes are essential for building broad shield volcanoes, because they can permit lava to travel great distances from an erupting vent. Eruptions at shield volcanoes are only explosive if water somehow gets into the vent.

Lava DomesLava Domes• Volcanic or lava domes are

formed by relatively small, bulbous masses of lava too viscous to flow any great distance; consequently, on extrusion, the lava piles over and around its vent. A dome grows largely by expansion from within. As it grows its outer surface cools and hardens, then shatters, spilling loose fragments down its sides.

Summary of Major PointsSummary of Major Points• The four types of volcanoes are the Cinder Cone

Volcano, Composite Volcano, Shield Volcano, and Lava Domes.

• Cinder cone volcanoes are built from particles and blobs of congealed lava ejected from a single vent.

• In a cinder volcano, as the gas-charged lava is blown into the air, it breaks into small pieces that solidify and fall around the vent to form a circular or oval cone.

• Composite volcanoes are formed by alternating layers of lava and rock fragments.

• The main feature of a composite volcano is a conduit system in which magma from a reservoir deep in the Earth's crust rises to the surface.

• Shield volcanoes are built almost entirely of fluid lava flows.

• Lava tubes are needed for making a shield volcano because they can let lava travel long distances from an erupting vent.

• Lava domes are formed by masses of lava. • As a lava dome grows , its outer surface cools and

hardens.

The EndThe End