Do Now:

1. What is convection?

2. In which layer does convection take place?

3. What is the heat source for convection?

4. Which layer makes up the tectonic plates?

5. What types of landforms are created at divergent boundaries?

6. What types of landforms are created at convergent boundaries?

VOLCANOES!!!!!!

• http://www.youtube.com/watch?v=jRfEGvp6wDU

• Take 1 minute to read the questions at the top of your guided video notes and be prepared to answer them in complete sentences during the video!

Map of Volcanoes around the WORLD!

Volcano Discovery

• http://webcams.volcanodiscovery.com/Kilauea

• This site allows you to look at what is currently happening around the world with volcanoes and earthquakes!

What is the difference between

magma and lava?• REVIEW: What is the type of rock that forms

when magma cools and hardens?

• What type of rocks forms when lava cools and hardens?

• THEY ARE BOTH TYPES OF IGNEOUS ROCK! What’s the difference?! –Think location…

Magma is below the Earth and forms intrusive igneous rock

Lava is what comes out of the volcano and forms extrusive igneous rock

How a volcano erupts is based on viscosity.

1. What is viscosity?• Viscosity is how resistant a substance is

to flowing. For example, honey is more viscous than water.

• Magma that contains more silica will be more viscous, magma that contains less silica will be less viscous.

Magma that is very viscous will explode, magma that is less viscous will flow.Lava that is hotter will be less viscous (like if you heat up honey) and will flow more.Lava contains dissolved gases, and if the lava is very viscous, those bubbles cannot expand. Instead, the bubbles will explode upwards.

Viscosi – what?!

• If the Shield volcano has faster flowing lava that creates new land, does it have a high viscosity or low viscosity?

• If the Composite Cone has a slower flowing lava that explodes due to the high content of silica, does it have a high viscosity or low viscosity?

HOT SPOTS!

• Volcanic regions that are fed by the mantle below and are much hotter than the mantle in other parts of the world

• Occur at divergent boundaries

Convergent vs. Divergent

• Divergent boundaries form hot spots – ex: Hawaiian islands and the RING OF FIRE – shield volcanoes, composite cones, etc.

• Convergent boundaries form volcanic island arcs. These form over subduction zones• The plate that is subducted releases water into

the overriding plate and causes some rock to melt – ex: Alaska volcanoes or Mt. St. Helens – cinder cones

• http://www.youtube.com/watch?v=9CxhOpk3J7Y

Anticipation Guide!

Volcanoes also eject pyroclastic materials,

• These particles can be as small as ash or as large as boulders.

There are 3 main types of

volcanoes, but they all have this

general form:

Shield Volcanoes

Shield Volcanoes

• Made of very fluid lava that spread really far and hardened.

• Broad shape

• Lots of island volcanoes (for example, Hawaii)

• Eruptions are not very violent

• Hot spot or subduction?

Cinder cone volcanoes

Cinder cone volcanoes

• Ejects lots of cinders (chunks of pyroclastic material) that accumulate at the bottom.

• Steep sides

• Short lifespans (usually only erupt once).

• Usually pretty small

• Hot spot or subduction?

Composite cone volcanoes

Composite cone volcanoes

• Huge!

• Produce both lava and pyroclastic material that can reach up to 120 mph!

• Usually found in the Ring of Fire, which is a zone of volcanoes that circles the Pacific Ocean.

• Can sometimes form lahars, which are mudflows that are made when lava mixes with water and soil.

• Hot spot or subduction?

Shape Review

Build your own virtual volcano

• Let’s explore some more and build our own virtual volcano to test eruption types

Let’s explore other types of volcanoes

Calderas• Calderas are volcanic depressions that

are created when the magma chamber is drained and the volcano collapses in on itself. Instead of looking like a mountain, it looks like a valley.

Volcanic necks

• Volcanic necks are formed when a volcano has been weathered down so that only the magma conduit (pipe) is left.

Lava plateaus are made from very low-viscosity lava flowing out of a fissure (crack) in the ground. The lava spreads really far and creates a flat landform.

Review:1. What is the relationship between the temperature

of magma and its viscosity? The higher the temperature, the more or less viscous the magma.

2. Name the three types of volcanoes AND list them in the order of least to most violent.

3. What region of the world are the most violent

volcanoes found?

4. Draw a diagram of a cinder cone volcano and lable the main parts (conduit, vent, crater, lava/pyroclastic material)