Volcanoes:Volcanoes:

DonDon’’t get all steamed about it…t get all steamed about it…

Magma Chamber

Lava

Vent

Lava Flow

Pyroclastic Flow

Q: What is a

Volcano?

1. Pressure increases as molten material fills

up the “magma chamber”

2. Molten materialfills up every

crack it can find

3. When it breaks throughthe surface, we get a

volcanic eruption!

4. Lava and other super hotmaterial flow out of the

volcano and onto the sides

A: Main Concept #3: Any place where heat and A: Main Concept #3: Any place where heat and ““molten materialmolten material”” From deep in the earth reaches the surface of the crust!!!From deep in the earth reaches the surface of the crust!!!

The basic process of an eruption is listed here:

Where you’ll likely find a Volcano

• Convergent plate boundary (large volcanoes)

• Divergent plate boundary (small volcanoes)

• “Hot spot” (various sizes but can be the biggest by far. This includes SUPERVOLCANOESSUPERVOLCANOES!!!!)

Volcanoes & Plate Boundaries

• Divergent & Convergent Plate Boundaries

You can see that volcanoes are forming where ocean crust dives under other crust

As the crust goes deeper, it gets melted!

As we have learned, hot stuff goes up!

If the melted crust (magma) gets to the surface…we get a volcano!

Hot Spots

Why do volcanoes form at hot spots?

Because there is hot material that wants to move up!

Why do hot spots form? Now that’s a good question!

We are not surewhy they occur…

A hot spot is where a large amount of molten materialIs trying to push it’s way up to the surface FAR FROM

A PLATE BOUNDARY!!!

Hawaii is a CLASSIC example of a hot spot

We can learn a lot from hot spots!

We can see the direction a plate ismoving by the line of volcanoes!

You can see that the Pacific plate has changed it’s direction of travel sometime in the past!!!

You can identify hot spots in two ways:

Volcanoes in the middle of nowhere (not near a plate boundary)

Older

Younger

A long line of volcanoes that get older in one direction

Hot spot

Plate Boundary

Volcanic HazardsVolcanic HazardsHey!

Where did my

car go?!

• Quiet Eruptions:– Lava flows from vents, setting fire and

burying everything in its path.– Covers large areas with a thick layer of lava.

Volcanic HazardsVolcanic Hazards

Quiet EruptionsQuiet Eruptions

Great. Now how are we

gonna get home?

Fig. 7.23a

Stephen Marshak

Volcanic Hazards Volcanic Hazards Quiet EruptionsQuiet Eruptions

Teachers, Please don’t mark your

students tardy – we have a bus that’s

running late.

**

Mt. Saint Helens

Mt. Saint Helens

Mt. Saint Helens

Mt. Saint Helens

Mt. Saint Helens

The Aftermath

You can see stumps that were trees sliced

in half by the force of the wind!

Here is an entire forest that wasdestroyed by the energy released

from the volcano!

Now we also have a river of hot mud instead of water!

The AftermathIt wasn’t just a small section of

forest that was destroyed!

The Aftermath

The air was so hot, these trees just started to burn spontaneously!!!

Rabaul Caldera on September 19, 1994

The amount of ash the volcano expelled almost covered this house!

U.S. Clark Air Base, Philippines, about 25 km east of Mount Pinatubo

The ash can travel 100’s of miles!!!

Pompeii was destroyed by Mt. Vesuvius in Italy

The people died before they couldrun away and their bodies left a

body shaped hole in the ash.

If you fill in the hole with cement, and then removed the ash, the cement shows the person who died there!

There is volcanic danger in Utah!!!

There are extinct volcanoes all over Utah

There are hot springsall over Utah

What about Yellowstone National Park?There are geysers…

And lots of hot springs…

How do you explain all this if there isn’t hotmaterial under the ground?

Here is a map showing

the areas that are in

danger if Yellowstonehas a major

eruption again!!!

Monitoring Volcanoes

• Because volcanoes have a lot of energy, we can use instruments to detect that energy to determine when she’s gonna blow!

Seismograph

Tilt Meter

Measures the shaking of the ground

If the ground begins to bulge

Volcanic Eruption Indicators

• Bulging & Tilt

• Increase in Earthquakes

• Increase in Temperature from underground water

• Out-gassing

• Many other indicators…

Main Concept #4: We can use indicators to determine if a volcano is likely to erupt

Fig. 7.15abc

W. W. Norton

Notice a bulge forming where the molten materialis trying to punch through

Dormant volcano (basicallyno molten material at this time)

Potentially active volcano (Magma fills chamber,

signs of possible eruption)

Active volcano (Molten material has

punched through)

Graphing the energy of a volcano

Energy of a volcano

0

5

10

15

20

25

30

35

40

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Days

En

erg

y

Energy

Earthquake 1

Earthquake 2Volcanic Eruption

Energy builds up over time Earthquakes release some Eruption releases most