question archive Lab Exercise: Identification of Igneous Rocks Every igneous rock has a story to tell that geologists can unravel by considering the rock’s texture and composition
Lab Exercise: Identification of Igneous Rocks Every igneous rock has a story to tell that geologists can unravel by considering the rock’s texture and composition
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Lab Exercise: Identification of Igneous Rocks
Every igneous rock has a story to tell that geologists can unravel by considering the rock’s
texture and composition. In this exercise, you will briefly tell the story of four of the igneous
samples you just identified—samples 4, 5, 6, and 9.
Instructions and Observations
Write a few lines about each of the rocks listed below, including the following information:
(1) Rock name
(2) Was this rock formed from felsic, intermediate, or mafic magma or lava? How do
you know?
(3) What type of plate boundary is associated with this type of magma/lava composition?
(4) What kind of eruption and volcanic structure is this type of magma/lava associated with?
(5) Where did this rock solidify? Underground? On Earth’s surface from extruded lava?
In midair as part of expelled pyroclastic material? How do you know?
(6) How relatively quick was this rock’s formation? Did it solidify in a one- or two-step
process? How do you know?
Sample #1:
The rock name is granite. The mixture of light-colored, felsic minerals with just a
few dark-colored mafic minerals means that it formed from felsic magma, which is
associated with convergent plate boundaries near subduction zones. This type of
magma is associated with explosive eruptions and stratovolcanoes. This rock’s
phaneritic texture means that it solidified slowly underground.
Sample #4: (2.5 points)
Sample #5 (2.5 points)
Sample #6: (2.5 points)
Sample #9: (2.5 points)
Lab 7 Igneous Rocks and volcanism II
