Name: _____________________________________________
Date: _________________________________
Density and Geology
Background: The density of rock is very important in the
field of geology. The difference in density of oceanic and
continental crust determines which tectonic plate will subducts under the other; the
density of magma determines whether a volcano will explode or gently erupt; the
density of heated rock makes melted crust float up to the surface and create granite
mountains…Understanding density can help predict geologic events and explain why
the world looks the way it does today.
In this lesson, you will be explaining why:

Tectonic plates subduct under each other.

Why super volcanoes erupt

Why tectonic plates move.
Earth Science Review:
1. What causes a volcano? Volcanoes are exits for hot melted rock that forces
its way through the crust. Underground, this
melted rock is called “magma.” Once it exits the
volcano, it is called “lava.”
2. What is the theory of plate tectonics? Earth’s
crust is broken into tectonic plates that move
around on the surface. These plates bump into
each other and can do one of 3 things: slide past each other, one slides under
the other (subducts), or both crash into each
other making a mountain. Oceanic crust is made
of basalt, and continental crust is made of
granite predominantly.
3. What is inside the Earth? The hard outer layer
of Earth is called the crust. Below that is the
solid mantle. Below the mantle is the liquid
outer core and the center of the Earth is the
inner core. The crust is the only cool layer. The other layers are
characterized by increasing heat and pressure.
Station 1: Supervolcanoes
Instructions:

Find the ars technica article online: “Earth’s devastating supervolcanoes
powered by density differences”
(http://arstechnica.com/science/2014/01/earths-devastatingsupervolcanoes-powered-by-density-differences/)

Answer the following questions:
1. Where is there a supervolcano in the United States?
____________________________.
2. How often do supervolcanoes erupt?
___________________________________________.
3. Why does the magma in the magma chamber eventually break through the
Earth’s crust?
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4. What makes supervolcano eruptions different from the typical volcano?
_________
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Supervolcanoes of the world.
Station 2: Subducting Plates

Complete the table below and then answer the questions.
Type of Rock
Mass
Volume
Density
Basalt
(oceanic crust)
Granite
(continental crust)
1. Which of the two types of crust is more dense?
__________________________________
2. Which will sink below the other when they collide? Use data above to
support your answer.
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3. Predict what happens when:
a. Continental crust collides with oceanic crust:
_____________________________________________________________
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b. Continental crust collides with continental crust:
_____________________________________________________________
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c. Oceanic crust collides with oceanic crust:
_____________________________________________________________
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4. When oceanic crust subducts under a continent, the plate melts when it
enters the mantle. What is going to happen to the density of the crust when
this heat energy is added?
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__
___________________________________________________________________
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5. Why do you think there are volcanoes along a subducting plate?
_________________
___________________________________________________________________
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Station 3: Mantle Convection Currents

Go to the following website:

http://maggiesscienceconnection.weebly.com/mantle-convection-platetectonics-earthquakes--volcanoes.html

Watch the first 3 videos on the right side of the screen and then answer the
questions.
1. Why does hot rock near the core become less dense? (Use the words “energy”
and “particles” in your answer)
____________________________________________________
___________________________________________________________________
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________________________
2. Why does the hot rock become denser when it reaches the crust? (Use the
words “energy” and “particles” in your answer.)
_______________________________________
___________________________________________________________________
___________________________________________________________________
________________________
3. What do you think will happen on the surface of Earth when the core finally
cools?
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4. The diagram below has arrows pointing to regions of the mantle. Draw a
particle diagram for each arrow.