Igneous Rocks Review and Practice

Pg 6,
ESRT

All igneous rocks form through the processes of MELTING and SOLIDIFCATION of minerals within/on top of Earth's crust

Pg 6,
ESRT

Extrusive Igneous Rocks

Intrusive Igneous Rocks

Formed as LAVA erupts from
volcanoes on Earth’s surface

AKA Volcanic environment of
formation

Cools quickly! (seconds to hours)

Formed as MAGMA intrudes into
Earth’s crust from the mantle

AKA Plutonic environment of
formation

Cools slowly! (days to millions of
years)

●Fine-grained (crystals too
small to see without
magnifying)

●Glassy texture

●Vesicular (air pockets/gas
bubbles)

●Coarse-grained (crystals
easy to see without
magnifying)

Characteristics

Formation

Extrusive Igneous Rocks

Intrusive Igneous Rocks

Vesicles (air bubbles/gas
pockets)

Glassy

Fine-grained

Coarse-grained
- crystals big
enough to see
without a
magnifying
glass!

Extrusive
rocks

Intrusive
rocks

Felsic rocks
(light color, low
density)

Mafic rocks
(dark color,
high density)

Estimating
percentages of
minerals within
igneous rocks.

1. Draw a line through
the rock name straight
down (vertically)
through the mineral
composition chart.

2. Estimate the
relative percentages
of each mineral using
the scale on the side.

3. Make sure that you
percentages total up
to 100!

35% potassium
feldspar
(100-65=35%)

38% quartz
(65-27=38%)

15% plagioclase
(27-12=10%)
7% biotite
5% amphibole

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Multiple Choice

Which processes lead directly to the formation of igneous rock?

• weathering and erosion

• heat and pressure

• compaction and cementation

• melting and solidification

Multiple Choice

A nonvesicular rock is made entirely of green 2-millimeter-diameter crystals that have a hardness of 6.5 and show fracture, but not cleavage. The rock is most likely

• shale

• phyllite

• dunite

• schist

Multiple Choice

Mineral crystals of quartz, biotite mica, and amphibole are produced primarily by the

• chemical reaction of elements in seawater

• deposition of sediments by a glacier

• cooling and solidification of magma

• metamorphism of bituminous coal

Multiple Choice

Which texture best describes an igneous rock that formed deep underground?

• glassy

• vesicular

• fine-grained

• coarse-grained

Open Ended

Identify two elements that can be found in both olivine and pyroxene.

Open Ended

Identify two processes that produce the igneous rock basalt.

Open Ended

Identify two elements that are commonly found in all three minerals in the data table.

Open Ended

Identify this igneous rock.

Open Ended

Two rocks, scoria and basalt, have formed from the cooled lava that erupted from the volcano, Nyiragongo. Describe the texture of each rock.

Multiple Choice

Which graph best represents the relative densities of three different types of igneous rock?

Open Ended

Identify the environment of formation of this igneous rock based on the size of its intergrown crystals.

Open Ended

Based on the minerals present, identify the relative color and density of this igneous rock compared to mafic igneous rocks with the same crystal size.

Open Ended

According to Bowen’s Reaction Series, how is the chemical composition of plagioclase feldspar found in basaltic rock different from the chemical composition of plagioclase feldspar found in granitic rock?

Open Ended

Describe the temperature conditions shown in Bowen’s Reaction Series that explain why olivine and quartz are not usually found in the same igneous rock type.

Open Ended

Identify one similarity and one difference between the igneous rocks andesite and diorite.