Name _______________________________________
Block _______
Igneous Rock Lab
1. Make a statement that compares the size of the crystal in each to the amount of time given to
complete the task.
The longer the time limit, the bigger the crystal.
2. The particles of magma are free to move around because the magma is
___________________ (solid/liquid).
3. When a substance (mineral or rock) becomes solid, the particles ___________________
(are/are not) free to move around and form crystals.
PART II – COOLING OF THE PIE
Read the following story:
A baker bakes three pies in an oven. After the pies are done, he turns off the oven and starts
to take the pies out of the oven. He takes the first pie out and puts it on the counter. As he is taking
the second pie out, he burns his hand and drops the pie into a sink of water. He leaves the third pie in
the oven while he takes care of his hand.
1. Which pie will cool the fastest? Explain why.
Pie in the sink because the water instantly cools it.
2. Which pie takes the longest to cool? Explain why.
Pie in the oven because the temp slowly decreases.
3. Igneous rocks form by the cooling of molten rock (magma or lava). What is the difference
between magma and lava?
Lava is above the earth’s surface. Magma is underground.
4. Apply the “pie story” to the different conditions in which molten rock would cool to form igneous
rock. Try to think of a scenario for each pie.
a. Counter pie Lava on the surface, touching air
b. Sink pie Lava hitting the ocean
c. Oven pie Magma underground
PART III – APPLICATION
Now, let’s think about real-life situations.
1. Where would molten rock take the longest to cool and change to solid? (on the surface, in the
water, in the Earth?) In the earth. Intrusive
2. Considering your answer to #1, what can you deduce about the size of the crystal grains
formed in this situation? Larger
3. Where would molten rock take the shortest time to cool and change to solid? (on the surface,
in the water, in the Earth?) In the water. Extrusive
4. Considering your answer to #3, what can you deduce about the size of the crystal grains
formed in this situation? Small crystals
5. Define the following:
a. Intrusive Cools inside the Earth
b. Extrusive Cools outside the Earth, on the surface
Match these terms to the situations in questions #1 and #3.
PART IV – USING TEXTBOOK INFORMATION
Answer the following using Chapter 6 Section 2.
1. Magma can be classified in three ways: _mafic_______________________,
_felsic______________________ and intermediate.
2. __Felsic______ magma is thick and slow-moving. It hardens into minerals such as quartz
and orthoclase feldspar. It is generally __lighter____________ in color.
3. ___Mafic_________ magma is hotter and thinner. It hardens into minerals hornblende,
augite, and biotite. It is generally _darker_____________ in color.
4. Intrusive igneous rocks form inside the Earth and cool (slowly, quickly) and thus form
(large, small or no) crystals. Igneous rocks with large crystals are said to be (coarse, fine) grained igneous rocks.
5. Extrusive igneous rocks form on the Earth’s exterior and have (large, small or no) crystals.
Extrusive igneous rocks with small crystals are said to have a _fine_______-grained texture.
Extrusive igneous rocks with no crystals are said to have __glassy___________ texture.
Some glassy textures have air holes.
PART V – IDENTIFICATION
Complete the following table using the rock kit samples.
NUMBER Crystal size
Fine=F
Coarse=C
1,2,3
7
10
13
16
Location
Intrusive=I
Extrusive=E
Color
Light=L
Dark=D
Magma
Type
Felsic=F
Mafic=M
Rock
Name
C
I
L
F
granite
C
I
D
M
gabbro
F
E
D
M
basalt
F
E
L
F
rhyolite
F
E
D
F
obsidian
Felsic even
though dark
in color.
19,20
21
F
E
L
F
pumice
F
E
D
M
scoria