Volcanoes : What is Volcanic Activity? - PowerPoint Presentation

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Volcanoes

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What is Volcanic Activity?

1. An opening in Earth’s crust through which molten rock, ash and gases erupt.2.Volcano: The landform that develops around the opening.

3. A way for Earth to release heat energy from the interior due to radioactive decay.

D. Peebles

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Types of Volcanoes?

1. Composite

2. Shield

3. Cinder

A. Heisey

G. Vaughn

USGS

Mt. St. Helens, WA

Mauna Loa, HW

Sunset Crater, AZ

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How Do Volcanoes Differ?

1. Size2. Shape

3. Composition4. Location

Tarbuck & Lutgens

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Questions

Which type of volcano is the widest?A. Cinder B. Composite C. Shield

What type of volcano typically produces the largest explosions? A. Cinder B. Composite C. Shield

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Composition

1. Magma viscosity

Silica content: more = thicker (most explosive)Temperature: higher= thinner

High Viscosity = thick, pasty

Low viscosity= Thin and runny

2.

Mafic

Little silica

low viscosity (runny)

Produces Dark color rocks

Ex.Basalt

3.

Felsic

Silica rich

High viscosity

Light color rocks

GraniteExplosive, high gas content4.

Pyroclastic- Fire Rock. What comes out of the volcano Explosive volcanic events.

D. Peebles, USGS

D. Weintraub

Kilauea, HW

Mt. St. Helens, WA

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Questions 3

Which variable determines how explosive a volcanic eruption will be?A. Gases B. Silica C. Temperature

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Types of Lava Flow

1. Flow types: depend on temperature and comp.Pahoehoe

: fast moving, hot lava, low viscosityAa Aa

: slower moving, cooler, higher viscosity

D. Peebles, USGS

J. Judd, USGS

J.D. Griggs, USGS

Aa Flow

J.D. Griggs, USGS

Pahoehoe Flow

http://www.youtube.com/watch?v=iyIV5fd1Aww

http://www.youtube.com/watch?v=Z9iW_oXMBB8

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Shield Volcanoes

1. Mafic lava (fluid)

nonexplosive eruptions, slow build upHot spots and ridges (mantle material)

2. Structure

Low angle slope Why ? Because the lava can travel long distances due to its fluidity. Low gas content!!

Tarbuck & Lutgens

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Questions

Shield volcanoes are composed of what type of lavas?Mafic B. Felsic C. Andesitic

The shape of a shield volcano is due to A. fluid, low viscosity lavas B. high viscosity lavas

C. pyroclastics D. gases

Shield volcanoes are usually associated with what landform feature/s or processes?

A. pyroclastic flows B. explosive eruptions

C. steep sided cones D. Gentle sloped cones

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Cinder Cones

1. Mafic lavas (can be felsic)

Large amt. pyroclasticsGentle & explosiveHigh viscosity

2. Structure

High slope

3. Deep crater

A. Heisey

Tarbuck & Lutgens

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Example: Paricutin

West of Mexico City1943 eruption beganCornfield of Dionisio Pulido

Earthquakes1st

day 130 feet

5

th

day +330 feet

Lava flows from base

Nine years of eruption

T. Nichols

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Cinder Cones

USGS G. Lewis

USGS G. Lewis

USGS G. Lewis

Fire Fountain=Pyroclastics

Parasitic Cone

Pelee’s Cinder Cone, HW

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Question

Cinder cones are mainly composed of -?- lavasMafic

B. Felsic C. Andesitic

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Composite Volcanoes

Felsic lavasLarge amt. pyroclastics

Viscous lavasExplosive / catastrophic eruptions

Subduction boundaries

Structure

Symmetrical cone

Medium to high slope

Ring of Fire

M. Giannechini

Pomerape & Parinacota, Chile

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Cascade Range

50+ eruptions in U.S. in past 200 years (mainly in Alaska)Pyroclastic Flows

Lahars

USGS

USGS

Pre 1980 Eruption

Post 1980 Eruption

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Questions

Composite volcanoes are composed of -?- lavas

Mafic B. Felsic C. Andesitic

The volcano with the steepest slope is a

Shield cone B. Cinder cone C. Composite cone

Volcanoes of the Cascade Range are mainly

Shield B. Cinder C. Composite

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Where are Volcanoes Located?

Tarbuck & Luntguns

UNAVCO

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Volcanoes Locations

Located along plate boundaries“Ring of Fire”- major volcanic belt, formed around the Pacific Ocean.

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3. Hot spots-stationary plume of magma continually rising through the crust from the athenosphere. Can occur in the middle of a plate.

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Check it out!

Looking at the current location of the Yellowstone hot

spot

1. If hot spots never move in which direction is the north American continent moving?

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Bell Ringer.

In your comp book draw a data table using a ruler, showing the following, Size, shape, composition, and Eruption type. Do this for the 3 types of volcanoes.

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Other Volcanic Features

Lava Plateaus

J. Shelton

D. Falconer

T. Bean

Lava Dome

Volcanic Neck

Rift Eruption

G. Vaughn

G. Vaughn

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Other Volcanic Structures

1. Plateaus- flat area caused by lava flow. 2. Volcanic necks- magma left in vent, extinct volcano

3. Dikes- molten material that vertically cut across rock layers4. Sill- molten material that horizontally cut across rock layers

Tarbuck & Luntgens

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4.

Laccoliths- domelike magma bulge under the surface.5. Batholiths- large rock structure, magma cools inside crust6. Active- erupting or will erupt soon.

7. Dormant- erupt in the future. 8. extinct- unlikely to erupt again

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Check Your Volcano Knowledge

What purpose do volcanoes serve on Earth?

What is magma?List three factors that determine the nature of a volcanic eruption.

What are the major gases released in volcanic eruptions?

What does

Pahoehoe

and Aa refer to?

What are the three types of volcanoes? Describe each one.

What type of materials make up pyroclastic flows?

Generally, where are volcanoes located on Earth?

How does a caldera form?

What are Lahars and what type of volcano are they usually associated with?

Which type of volcano is the most explosive?

Name and describe three other igneous features.

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Calderas

USGS G. Lewis

USGS G. Lewis

Crater Lake, OR

Long Valley, CA

Mauna Loa, HW

1. Huge hole left by the collapse of a

volcano

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Classwork Page 227 & 228

Page 227 Concept MapPage 227 & 228 1-16, 17, 19, 21-24 Rewrite question as part of the answer.Page 229 1-6 Rewrite question as part of the answer.

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