E3.P3XC Unit: Volcanoes Powerpoint on the standards for Volcanoes.

E3.P3XC Unit: Volcanoes

Powerpoint on the standards for Volcanoes

Volcanic Eruptions• Volcano- mountain formed from molten

magma forced through the Earth’s surface• Magma- Molten rock material

Do you think that most volcanoes have explosive or non-explosive eruptions? Why?

• Most volcanic eruptions are Non-Explosive!

• Types of Eruptions– Non-Explosive• Lava- magma that reaches Earth’s surface• Lava flows happen with non-explosive eruptions

– Explosive• Shoots hot debris and gases• No lava flows, but massive debris• Dust clouds up the atmosphere

Explosive V. Non-Explosive

List a few characteristics of each type of explosion. Be prepared to share!

Cross Section of a Volcano

• Volcanoes form around vents that release magma

Magma!

• Explosive Magma!– High water content– High silica content• Creates an eruption with stiff

magma and releases gases

What Erupts?• Pyroclastic Material – – hot debris from the volcano

• Four types of Lava:1. Blocky Lava2. Pahoehoe3. Aa4. Pillow

1. Blocky Lava– Cool, stiff lava– Doesn’t travel far

2. Pahoehoe– Slow flowing lava– Like dripping wax– Forms glassy surface

3. Aa– Hawaiian for “Jagged

Lava”– Forms jagged– Underneath continues

to move

4. Pillow Lava– Forms underwater– Rounded, bubble

lumps

Types of Pyroclastic Material

1. Volcanic Blocks- Largest pieces- Solid Rock

2. Volcanic Bombs- Blobs of magma that harden in the air

3. Lapilli -Little stones -Pebbles

4. Volcanic Ash-gases expand rapidly and shoot hot ash

Which type of Pyroclastic material is most harmful to the environment? Why?

Assignment1. What are the four types of lava?2. What are the types of pyroclastic material?3. How is pyroclastic material categorized?4. Why do you think that volcanic eruptions

with water are explosive?5. Draw a non-explosive erupting volcano

including its vents.

What Causes Volcanoes

Chapter 9 Sec 3

Formation of Volcanoes

• Volcanoes are formed by the build up of cooled lava and other pyroclastic materials

• Magma is a mixture of liquid and solid rock material at high temperatures

• A large number of volcanoes lie on the plate boundaries

What are the three types of plate boundaries?Transform, Divergent, Convergent

• Boundaries– Volcanoes form at boundaries where tectonic action is

at– Ring of Fire!• Area of immense volcanic activity Surrounding the Pacific Plate

When Plate Separate• What boundary is associated with plate

separation?Divergent!

• Magma rises through the rift in the ocean floor forming new crust

• Produce what underwater sea features? Mid-Ocean Ridges

DID YOU KNOW…. Divergent boundaries can also be continental. It’s rare, but true!

When Plates Collide!• Which boundary is associated with plate

collision?Convergent!

• Common where oceanic subducts under continental crust

• Oceanic plate moves downward, melts in the mantle, forms magma

• Magma rises to the surface and forms volcano!• Why do oceanic plates always subduct beneath

continental?Oceanic is denser than continental!

Hot Spots• Hot Spots- weak areas of crust where magma

comes through – The Hawaiian islands are formed from volcanic

activity, but are no where near a plate boundary!

• Hot Spots often produce chains of volcanoes as the Hot Spot remains permanent and the plate moves over it.

• Is it possible to live on a previous hot spot?Yes! Hawaiians do so daily!

Predicting• Extinct- A volcano that hasn’t erupted in

recorded history• Dormant- A volcano that has not erupted in

some time• Active- have shown signs up erupting

• Before become active, what type of volcano was Dante’s Peak?

Dante’s Peak was dormant. Goes to show you, always proceed with caution!

• Signs of Eruption1. Eruptions are preceded by many small quakes2. The Volcano’s slop may bulge indicating a build up in

the magma chamber3. Increase levels of volcanic gases4. Infrared images from outer space show temperature

changesWhat two gases did Pierce Brosnan detect on Dante’s Peak?Sulfur Dioxide and Carbon Dioxide, both are common volcanic gases used for detection today

Assignment1. Please draw and label the convection currents of

the mantle.2. What are the four main predictions for volcanic

activity?3. Where are most divergent boundaries found?4. Why do oceanic crusts always subduct under

continental crust?5. How do Hot Spots leave a string of volcanoes?6. What is the difference between extinct and

dormant volcanoes?