Volcanoes – Day 2

Earth Science10/7/10

Announcements

• We will have a QUIZ tomorrow on Volcanoes!

• Vocabulary for Chapters 8 and 10 are due TOMORROW!

• Remember, this is the time to make a NEW start and get a good grade for this new report card!

Objectives

• I will be able to relate plate tectonics to volcanoes by describing ________________ __________________________, the types of boundaries that produce volcanoes.

• I will be able to _____the locations of volcanoes on a map and compare patterns of volcanoes to plate tectonics.

Key Points• Magma composition plays a major part in determining

the form of a volcano.• Magma forms when solid rock in the crust and upper

mantle melts.• The composition of the material, water content and

confining pressure are factors that affect the melting point of rock.

• Magma tends to rise towards Earth’s surface primarily because rocks become less dense when they melt.

• Most of the active volcanoes on Earth are located in a belt known as the ring of fire.

• Identify an O-C plate boundary creating a volcano.

How Volcanoes Form

• How Volcanoes Form Video

Magma

• As we know, ________________plays a major part in determining the __________of a volcano.

• But where does magma come from?• Magma forms when __________in the crust

and upper mantle ________.

Magma• How does rock melt?

– There are ________factors that contribute to rocks melting, or the formation of magma.

1. ________– As you go ______in the earth, the temperature _____.– Subduction creates friction and causing heat– As magma ________, it heats rocks closer to the

earth’s surface.• But this alone is ____________to create all of the

magma that we know exists below the earth’s crust…

Magma

2. Confining ___________– As confining pressure is __________, the melting

temperature of rocks is ________.– This means that as rocks can __________as they

are released from the confining pressure deep within the earth.

– This process is called _____________________

Magma

3. __________Content– Water in rocks can cause a rock to melt at

_________temperatures.– Rocks with more water in them melt easier than rocks

that are “dry”.

• BOTTOM LINE: The _____________ ________________, ________content and confining ________are factors that affect the __________________ of rock.

Magma

• Now that we know how magma forms, why does it come to the surface of the planet?

• Let’s discuss.• Write down what you think:

__________________________________ __________________________________

Magma

• Magma tends to rise towards Earth’s surface primarily because ______________________ ____________________________________.

• What does that mean? When rocks change from a solid state to a liquid state, they become _____________!

• What is lighter will rise, just like heavy things sink!

Plate Tectonics and Volcanoes

• Most of the active volcanoes on Earth are located in a belt known as “____________”.

• Others are located seemingly sporadically around the globe.

• Scientists could not explain the worldwide distribution of volcanoes until the introduction of the theory of ___________________________.

The Ring of Fire

• Watch a slideshow of the Volcanoes on the Ring of Fire HERE!

Plate Tectonics and Volcanoes• Plate movement forms volcanoes in three zones:1. ___________Plates

– Ocean – Ocean• Rising magma can form volcanic ________arcs in

an ocean (Aleutian Islands).– Ocean – Continent

• Rising magma can form __________volcanic arcs (Andes Mountains).

Convergent Boundary Volcano

Mount St. Helens emitting volcanic ash 2 months after it’s May eruption in 1980.

Was type of convergent boundary caused Mt. St. Helens?

How do you know?

Plate Tectonics and Volcanoes2. __________Plate Boundaries

– When plates pull apart, there is less pressure on the rocks below.

– Because of the ________________, rocks melt and magma is formed.

Plate Tectonics and Volcanoes3. Intraplate Igneous Activity (non boundary)

– Intraplate means activity _______a tectonic plate _______from plate boundaries.

– This is caused by ________________. – Examples of this are the ____________________

Kilauea, an Intraplate Volcano

Mapping Volcanoes Lab

Follow the directions on the handout to map volcanoes around the world.

After you finish plotting the volcanoes, answer the questions in complete sentences.

Check In – Answer on a separate piece of paper in COMPLETE

sentences.• Most of the active volcanoes on Earth are

located where?

• Explain how magma forms.

• What three things affect the melting point of a rock?

• Why does magma rise to earth’s surface?