Lab 3 On Igneous Rocks,
Should take about 1.5 hours
Is for geology.
Must be done in a timely manner, must be well organized and have the motivation for lab.
Must submit in pdf and docx format.
Lab instructions are attached.
GEOL4
Igneous Rocks
NAME_______________________________________________
Part 1: Melting and Plate Boundaries
1. Open a web browser (e.g. Google Chrome) and go to www.google.com/maps
2. In the lower left-hand corner there will be an icon (box) labeled, “Satellite.” Click on this
icon to change the view to Satellite imagery.
3. Complete the table on page 2 using the terminology from the table below by:
a. typing the location listed into the search bar in the upper left-hand corner and
examining that region of the world.
b. zooming in and out to fully examine the area, looking for the features (i.e. evidence)
associated with each type of plate boundary, as listed below.
Plate Boundary Type
Surface Features
Dominant Melting Process
Divergent Boundary on
oceanic lithosphere
Mid-ocean ridge (MOR)
Decompression
Divergent Boundary on
continental lithosphere
Continental rift
Decompression
Convergent Boundary with
Subduction (O-O)
•
•
Oceanic Trench
Volcanic island arc
Partial Melting
Convergent Boundary with
Subduction (O-C)
•
•
Oceanic Trench
Continental volcanic arc
Partial Melting
Convergent Boundary
without subduction (C-C)
•
•
Continental collision zone
Huge and tall (high
elevation) mountain
ranges
High (elevation) plateaus
Some melting by burial
and/or addition of water (not
related to subduction), but
few if any volcanoes because
magma typically does not
reach the surface.
See also Transform Boundary
(oceanic lithosphere)
•
Addition of Water
Addition of Water
Transform Boundary on
oceanic lithosphere
Mid-ocean ridge (MOR)
Transform Boundary on
continental lithosphere
Offset features on the land
surface, such as river valleys,
road, etc. (due to strike-slip
faulting)
N/A
N/A
Hot Spots (volcanoes far
from plate boundaries)
Decompression
1|Page
N/A
See also Divergent Boundary
(oceanic lithosphere)
GEOL4
Igneous Rocks
4. Complete the following table by:
a. typing the location listed into the search bar in the upper left-hand corner and
examining that region of the world.
b. zooming in and out to fully examine the area, looking for the features (i.e. evidence)
associated with each type of plate boundary, as listed below.
Location
(type location into
Google Maps
search bar)
Mid-Atlantic Ridge
Yellowstone
National Park, WY
Philippine Trench
Great Rift Valley
Peru-Chile Trench
Himalayas
San Andreas Fault
2|Page
Surface Features
(see list above)
Type of Plate Is Melting
Boundary
Occurring
at this
Plate
Boundary
(Yes or
No)?
If Melting Is
Occurring, What
is the Dominant
Type of Melting
Process? (see list
above)
GEOL4
Igneous Rocks
Part 2A: Intrusive vs Extrusive Igneous Rocks
1. Intrusive Igneous rocks cooled from a magma BELOW OR ABOVE (circle one)
Earth’s surface; whereas, Extrusive Igneous rocks cooled from a lava BELOW OR
ABOVE OR VERY CLOSE TO (circle one) Earth’s surface.
2. TRUE OR FALSE (circle one): Extrusive Igneous rocks cooled more slowly than
Intrusive Igneous rocks.
3. TRUE OR FALSE (circle one): In general, Intrusive Igneous rocks will have larger
(more visible) crystals (minerals) than Extrusive Igneous rocks due to the respective
cooling histories of Intrusive and Extrusive Igneous rocks.
4. TRUE OR FALSE (circle one): An Intrusive Igneous rock that cooled very close to the
Earth’s surface could have an extrusive texture, such as aphanitic, because the rocks close
to the Earth’s surface are relatively cold compared to those deeper below the Earth’s
surface.
5. Porphyritic Igneous Rocks have 2 distinct crystal sizes. If one crystal size is visible to
the naked eye, but the other is not it is likely that this rock cooled SLOWY
OR
QUICKLY OR SLOWLY THEN QUICKLY (circle one).
6. The following terms are a list and summary of common Igneous Rock Textures: Fill in the
table on the next page by writing the type of textures possible for Intrusive Igneous Rocks
and Extrusive Igneous Rocks. Hint: consider crystal size and cooling history.
Textures:
• Phaneritic: crystals (minerals) visible to the naked eye with an interlocking
texture
• Vesicular: visible holes (vesicles) on the surface and/or throughout the rock
• Glassy: looks like glass; shiny; no crystals (minerals)
• Pegmatite: very large crystals (minerals) visible to the naked eye that are at least
1 cm in diameter
• Aphanitic: crystals (minerals) not visible to the naked eye; may have a grainy
appearance
• Porphyritic: two distinct crystal (mineral) sizes
3|Page
GEOL4
Igneous Rocks
Intrusive Igneous Rock Texture
Extrusive Igneous Rock Texture
Part 2B: Composition
1. Draw a line matching the following compositions to the appropriate description of the
composition
4|Page
•
Felsic
•
Intermediate
•
Mafic
•
Ultramafic
a. Light-colored (e.g. pink,
light-purple, white) due to
relatively high concentrations
of silica (Si) and potassium
(K), but relatively low
concentrations of iron (Fe)
and magnesium (Mg)
b. Green or greenish-black
colored due to very high
concentrations of iron (Fe)
and magnesium (Mg), but
very low concentrations of
silica (Si) and potassium (K)
c. Grey or black and white
colored due to intermediate
concentrations of silica (Si),
potassium (K), iron (Fe),
magnesium (Mg)
d. Dark-colored (black or darkgrey) due to relatively high
concentrations of iron (Fe)
and magnesium (Mg), but
relatively low concentrations
of silica (Si) and potassium
(K)
GEOL4
Igneous Rocks
Part 2C: Igneous Rock Identification
Follow the link and watch each of the videos in the folder for each igneous rock:
https://www.dropbox.com/sh/g6z62jd9d0r9vqg/AABW61MHoYucJIKflVB8Cn4da?dl=0
Use the flow chart on page 6 to identify your samples. List your answers in the table below.
Sample Composition:
#
(F=Felsic, I=Intermediate,
M=Mafic, U=Ultramafic)
1
2
3
4
5
6
7
8
9
10
11
12
5|Page
Texture (see
list above)
Review pages
3, 4, and 6
Igneous
Rock Name
Intrusive (I) or
Extrusive (E) or
Both (I & E)
Hint: use texture.
Cooling History
(Fast, Slow, or
Slow then Fast)
Hint: use texture.
GEOL4
Igneous Rocks
IGNEOUS ROCK IDENTIFICATION FLOW CHART
START HERE – What is the composition of the rock?
Dunite
Felsic – light colored (e.g.
pink, purple, white, light grey)
(includes orthoclase, quartz,
muscovite, biotite, and/or
amphibole)
Intermediate – greyish
or black & white
(includes plagioclase,
quartz, orthoclase,
muscovite, biotite, and
/or amphibole)
Can you see any visible crystals?
Yes
Is the entire rock made up
of visible crystals with an
interlocking (puzzle-piece
fit) texture?
No, visible and
fine-grained
crystals =
Porphyritic
Granite
Porphyritic
Rhyolite
Is the sample Glassy?
Yes
Obsidian
Yes
No = Aphanitic
6|Page
No
Yes =
Phaneritic
Gabbro
Yes
Is the entire rock made
up of visible crystals with
an interlocking (puzzlepiece fit) texture?
Yes =Phaneritic
Diorite
If yes go to the Felsic
category and start over.
This rock looks mafic,
but is actually felsic.
No, visible and
fine-grained
crystals =
Porphyritic
Porphyritic
Andesite
No = Aphanitic
Rhyolite
No
Andesite
Is the sample Vesicular?
Pumice
Can you see visible crystals?
Is the sample Glassy?
No
Yes
Mafic – black, dark grey, or
reddish (includes plagioclase,
Augite, and/or Olivine)
Can you see any visible crystals?
No
Yes =
Phaneritic
(Pegmatite
if ≥ 1 cm)
Ultramafic (dark green or
bright green) with visible
olivine crystals (i.e. phaneritic)
Yes
Scoria (may be
reddish in color)
Is the sample Vesicular?
Yes
Is the sample lightweight,
frothy (has numerous
vesicles), rough to the
touch?
No
Vesicular
Basalt
No, and
no visible
crystals =
Aphanitic
Basalt
No, visible and finegrained crystals =
Porphyritic
Porphyritic Basalt