Welcome to Science 10/25• Get out your lab sheet. You have 3 minutes

to create the type of volcano listed on your card. Have your group help you if needed.

• Today’s Schedule• 1. Finish/Review Volcano Types Lab• 2. Outline/Notes Volcanic Eruptions• 3. Yokum Construction Co. will be open for

business to sell building materials.

Volcano TypesVolcano Types• Shield, Cinder-Cone, and Composite.

• What causes these different types of volcanoes to form?

• The different ways in which they erupt and the different materials that are erupted.

Volcanic EruptionsVolcanic EruptionsSection. 3Section. 3

PelePele

I. Kinds of Volcanic EruptionsI. Kinds of Volcanic Eruptions• Eruptions are classified as either quiet or

explosive.

• How a volcano erupts depends on the gasses, silica, and viscosity of the magma.

• Silica-similar to sand, one of the key components of

magma• Viscosity- the resistance of a

liquid to flow

II. How the Eruption WorksII. How the Eruption Works• A volcanic eruption is similar to an exploding

pop can.

• Gasses inside the volcano build up. As gas builds up, so does the pressure. When the pressure is too great, the volcano erupts.

BBC NEWS | Science/Nature | Animated guide: Volcanoes

• OUR RESTLESS PLANET

III. Quiet EruptionsIII. Quiet Eruptions• Magma has low silica,

low viscosity, and low gasses so it flows easily.

• Hawaiian Islands were made this way.

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• What type of volcano is formed by quiet eruptions?

• Shield

IV. Explosive EruptionsIV. Explosive Eruptions• Magma has high-silica

and high viscosity, making it thick and sticky. High Gas.

• Magma does not flow.• Builds up in the pipe

like a cork in a bottle . • Pressure builds up until

the volcano explodes.• :: Make a Volcano

Mount St. HelensMount St. Helens mt. st. helens - Google Videos#

During Eruption

Mount St. Helens Mount St. Helens Before Eruption After Eruption

"Mt. Saint Helens' Powerful Erruption"

Mt. St. Helens 2003Mt. St. Helens 2003

Mt. St. Helens 1984

V. Explosive EruptionsV. Explosive Eruptions• Explosive eruptions break lava

into fragments that quickly cool into pieces of different sizes.

• Large pieces = bombs• Small pieces = cinders

• Pyroclastic flow- mixture of hot gas, ash, cinders, and bombs

• -pyroclastic-flow-video.htm

VI. Stages of Volcanic ActivityVI. Stages of Volcanic Activity• Active, dormant, or

extinct?• Active- erupting or shows

signs of erupting.• Dormant- may awaken in

the future.• Extinct- unlikely to erupt

again

• Is a volcano ever really extinct?

• No, at anytime a volcano thought to be extinct could reawaken.

How It All StartsHow It All Starts• Magma from the mantle

rises up through the crust because it is less dense.

• Magma becomes trapped beneath layers of rock.

• Weak spots in the crust allow trapped magma to reach the surface, forming a volcano.

At the SurfaceAt the Surface

• Magma Chamber- pocket of magma beneath a volcano

• Pipe- long tube that connects the magma chamber to the surface

• Vent- opening where molten rock and gas leave the volcano

Pipe, Vent, Magma Chamber, Crater, Lava Flow

At the SurfaceAt the Surface

• Lava flow- area covered by lava as it pours out of a vent.

• Crater- bowl shaped area that may form at the top of a volcano.

Question of the DayQuestion of the Day• Correctly the match the

stages of volcanoes with the definitions.

• A. A volcano that is unlikely to erupt again.

• B. A volcano that is erupting or shows signs of erupting.

• C. A volcano that may awaken in the future

• Active

• Dormant

• Extinct

Today’s ObjectivesToday’s Objectives

• 1. Question of the Day

• 2. Open book quiz

• 3. Continue research on volcanoes