Volcanoes – Day 2
Earth Science
10/7/10
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
Was type of
convergent
boundary
caused Mt. St.
Helens?
How do you
know?
Mount St. Helens emitting volcanic ash 2 months
after it’s May eruption in 1980.
Plate Tectonics and Volcanoes
2. __________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 Volcanoes
3. 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.