Volcanoes and Plate Tectonics

A weak spot in the crust where molten material, or magma comes to the surface

Volcano

A molten mixture of rock-forming substances, gases, and water from the mantle

Magma

When magma reaches the surface

Lava

A major volcanic belt formed by many volcanoes that rim the Pacific Ocean

Ring of Fire

Along the boundaries of diverging plates such as mid-ocean ridges

Where do most volcanoes form?

Along the rift valley lava pours out of cracks in the ocean floor

How do volcanoes form against mid-ocean ridges?

True

True or False

Volcanoes can form along diverging plate boundaries on land

True

True or False

Many Volcanoes form near converging plate boundaries where oceanic crust returns to the mantle

Older denser plates sink beneath a deep ocean trench into the mantle. Some rock above, subducting plates melt and forms magma. Magma is less dense so it comes up eventually breaking through the ocean floor creating a volcano

How does subduction at converging plate boundaries lead to the formation of volcanoes?

Volcanoes at boundaries where two oceanic plates collide creating a string of islands

Island Arc

Japan, New Zealand, Indonesia, Philippines, Carribean Island

What are the major arcs?

a continental plate and an oceanic plate

What plates collided to form the Andes Mountains on the west coast of South America?

Where material from deep within the mantle rises and melts(the start of a volcano)

Hot Spot

Pacific plates drifted over a hot spot where Hawaii is now located

How did the Hawaiian Islands form?

False, also continental crust

True or False

Hot spots form only under oceanic crust

A substance that cannot be broken down into other substances

Element

True

True or False

When frozen water melts, it is undergoing a physical change

1) When paper is burned, it forms ashes

2) An iron chair will develop rust if oxygen combines with the iron

What indicates a chemical property?

milk and orange juice

What liquids have low viscosity?

Depends on silica content and temperature

What factors determine the viscosity of magma?

1) It makes magma thicker

2) It produces light-colored lava

What does silica do?

a rock that forms from light-colored lava

Rhyolite

a rock that forms from low-silica magma

Basalt

Hot, fast-moving lava

Pahoehoe

Cool, slow-moving lava

aa

Viscosity decreases

What happens to viscosity as temperature increases?

the temperature is lower and the silica content is higher

What happens when the viscosity of magma is higher?

the temperature is higher and the silica content is lower

What happens when the viscosity of magma is lower?

False, asthenosphere

True or False?

Magma forms in the lithosphere

True

True or False?

Liquid magma rises until it reaches the surface, or until it becomes trapped beneath the layers of rock.

1) pocket of magma beneath the surface

2) crack to the surface

What do all volcanoes have in common?

the area covered by lava as it pours out of a vent

What is lava flow?

at the top of a volcano around the central vent

Where does a crater form?

Carbon dioxide dissolved in soda pop rushes out when the pop is opened

What is a good model of a volcano erupting?

You cannot see the carbon dioxide gases but once the rock releases from pressure the carbon dioxide releases and allows the volcano to explode

What happens during a volcanic eruption?

The force of the expanding gases push the magma from the chamber through the pipe until it flows or explodes out of the vent

What factors determine the force of a volcanic eruption?

False, low in silica

True or False?

A volcano erupts quietly if its magma is thick and sticky.

Fine rocky particles as small as a speck of dust

Volcanic ash

Pebble-sized particles

Cinders

Particles ranging from the size of a baseball to the size of a car

Bombs

Occurs when an explosive eruption hurls out a mixture of hot gases, ash, cinders, and bombs (surge)

What is pyroclastic flow?

False, far away too

True or False?

Volcanic eruptions cause damage only when they are too close to the crater's rim.

Can belch out hot clouds of deadly gases as well as ashes, cinders, and bombs, can bury entire towns, if wet roofs will collapse, jet plane engines may stall from ash, cause landslides

What kinds of damage can volcanoes cause?

True

True or False?

The activity of a volcano may last from less than a decade to more than 10 million years.

False

True or False?

Most long-lived volcanoes erupt continuously.

Unlikely to erupt ever again

Extinct Volcano

No longer active but may become active again

Dormant Volcano

Erupting or showing signs that it soon will erupt

Active Volcano

False, anytime

True or False?

The length of time between eruptions of a dormant volcano is always less than a thousand years.

It can happen at anytime but that also means it may not be for another 100 years so they could live in fear

Why might people living near a dormant volcano be unaware of the danger?

1) Geologists are more successful in predicting volcanic eruptions than earthquakes

2) Geologists cannot predict what type of eruption a volcano will produce

What goes into the factor of predicting volcanoes?

1) Shield Volcanoes

2) Cinder Cone Volcano

3) Composite Volcanoes

4) Lava Plateaus

What are four landforms that form from ash and lava?

They form from many thin layers of lava

What is true about shield volcanoes?

False, ,shield volcanoes

True or False?

The Hawaiian Islands are cinder cone volcanoes.

Mount Fiji in Japan and Mount St.Helens in Washington state

Name two examples of composite volcanoes

True

True or False?

A composite volcano has both quiet and explosive eruptions

Gently sloping mountain formed by repeated lava flows

Shield Volcano

Cone-shaped mountain formed form ash, cinders, and bombs

Cinder Cone

Mountain formed by lava flows alternating with explosive eruptions

Composite Volcano

High, level area formed by repeated lava flows

Lava Plateau

Hole left by the collapse of a volcanic mountain

Caldera

It releases potassium and phosphourus

What happens when volcanic ash breaks down?

1) Volcanic Neck

2) Dikes

3) Sills

4) Batholiths

5) Dome mountains

What are 5 features formed by magma?

A mass of rock formed when a large body of magma cools inside the crust

Batholith

Baja, Sierra Nevada, Idaho, British Colombia

Where is an example of batholith in the United States?

True

True or False?

A dome mountain forms when hardened magma is uplifted and pushes up horizontal layers of rock.

True

True or False?

Some types of volcanic activity do not involve the eruption of lava.

When groundwater heated by a nearby body of magma rises to the surface and collects in a natural pool

Hot Springs

A fountain of water and steam that erupts from the ground

Geyser

Steam from underground is piped into turbines

How can geothermal energy be converted to electricity?

Bowl-shaped area that forms around a volcanoes central vent

Crater

Material found in magma that is formed from oxygen and silicon

Silica

When magma reaches the surface

lava

Slab that forms when magma forces itself across rock layers

Dike

Slab that forms when magma squeezes between layers of rock

Sill