Warm Up Warm Up 1) The three groups of rocks are classified by ____. a. how they formed c. color b. grain size d. chemical composition 2) Which of the following is true about rocks? a. Rocks do not contain any nonmineral matter. b. Rocks are composed of only one mineral. c. Coal is not considered a true rock. d. Most rocks are a mixture of minerals. 3) What type of rocks are formed by processes powered by the sun ? a. No rocks are formed by energy from the sun. b. sedimentary rocks c. igneous rocks d. metamorphic rocks Answers: 1) a. 2) d. 3) b.
Transcript
Warm UpWarm Up1) The three groups of rocks are classified by ____.
a. how they formed c. colorb. grain size d. chemical composition
2) Which of the following is true about rocks?a. Rocks do not contain any nonmineral matter.b. Rocks are composed of only one mineral.c. Coal is not considered a true rock.d. Most rocks are a mixture of minerals.
3) What type of rocks are formed by processes powered by the sun?a. No rocks are formed by energy from the sun.b. sedimentary rocksc. igneous rocksd. metamorphic rocks
Answers: 1) a. 2) d. 3) b.
Igneous RocksIgneous Rocks
Chapter 3, Section 2Chapter 3, Section 2
Formation of Igneous RocksFormation of Igneous Rocks
Rocks that form when magma hardens Rocks that form when magma hardens beneath Earth’s surface are called beneath Earth’s surface are called intrusive igneous rocksintrusive igneous rocks
They have They have intrudedintruded into the existing into the existing rocksrocks
As magma rises it cools, allowing As magma rises it cools, allowing elements to combine and form elements to combine and form minerals, which combine to form minerals, which combine to form igneous rocksigneous rocks
When lava hardens, the rocks that form When lava hardens, the rocks that form are called extrusive igneous rocksare called extrusive igneous rocks
The have The have extrudedextruded onto the surface onto the surface
Evolution of a Evolution of a MagmaMagma
Formation of Igneous RocksFormation of Igneous Rocks
Intrusive - Granite
Extrusive - Rhyolite
Classification of Igneous Classification of Igneous RocksRocks
Texture and composition are two Texture and composition are two characteristics used to classify characteristics used to classify igneous rocksigneous rocks
Texture describes the appearance of Texture describes the appearance of an igneous rock based on its size, an igneous rock based on its size, shape, and arrangement of shape, and arrangement of interlocking crystalsinterlocking crystals
Composition describes the proportions Composition describes the proportions of light and dark minerals in the rockof light and dark minerals in the rock
If the magma cools slowly, it will have If the magma cools slowly, it will have only have a few centers of crystal only have a few centers of crystal growthgrowth
Slow cooling results in the formation of Slow cooling results in the formation of large crystals (course-grained)large crystals (course-grained)
If magma or lava cools rapidly, a large If magma or lava cools rapidly, a large number of tiny crystals compete for number of tiny crystals compete for available ionsavailable ions
Rapid cooling of magma or lava results Rapid cooling of magma or lava results in rocks with small, interconnected in rocks with small, interconnected mineral grains (fine-grained)mineral grains (fine-grained)
Glassy Texture – solids produced so Glassy Texture – solids produced so quickly that the ions are not able to quickly that the ions are not able to alignalign
Porphyritic Texture – rocks that have Porphyritic Texture – rocks that have different size minerals, a result of different size minerals, a result of different rates of coolingdifferent rates of cooling
Concept CheckConcept Check How does the rate of cooling of magma How does the rate of cooling of magma
or lava affect the texture of igneous or lava affect the texture of igneous rocks?rocks?
A slowly cooling magma or lava will A slowly cooling magma or lava will produce rocks in which the mineral produce rocks in which the mineral grains are relatively large. Quickly grains are relatively large. Quickly cooling molten material will result in cooling molten material will result in rocks with small mineral grains. Lava rocks with small mineral grains. Lava that cools rapidly will produce a glassy that cools rapidly will produce a glassy rock. Rocks that form as a result of rock. Rocks that form as a result of different cooling rates will have both different cooling rates will have both large and small mineral grains.large and small mineral grains.
Granitic Composition – Igneous rocks Granitic Composition – Igneous rocks in which quartz and feldspar are the in which quartz and feldspar are the dominant mineralsdominant minerals
Most granitic rocks also contain Most granitic rocks also contain about 10% dark silicate minerals and about 10% dark silicate minerals and 70% light silicate minerals70% light silicate minerals
Basaltic Composition – rocks that Basaltic Composition – rocks that contain many dark silicate mineralscontain many dark silicate minerals
Basaltic rocks are rich in iron and Basaltic rocks are rich in iron and magnesiummagnesium
Other Compositional GroupsOther Compositional Groups
Andesitic Composition – rocks with a Andesitic Composition – rocks with a composition between granitic and composition between granitic and basalticbasaltic
Andesitic rocks contain at least 25% Andesitic rocks contain at least 25% dark silicate mineralsdark silicate minerals
Ultramafic – rocks that are composed Ultramafic – rocks that are composed mostly of dark silicate mineralsmostly of dark silicate minerals
Peridotite is an example of an Peridotite is an example of an ultramafic rock, although rare on the ultramafic rock, although rare on the crust, it is thought that the mantle is crust, it is thought that the mantle is made mostly of peridotitemade mostly of peridotite
Other Compositional GroupsOther Compositional GroupsAndesitic Composition - Andesite
Ultramafic - Peridotite
Bowen’s Reaction SeriesBowen’s Reaction Series
Classification of Igneous Classification of Igneous RocksRocks
Concept CheckConcept Check
Describe the main differences Describe the main differences between granitic and basaltic rocks?between granitic and basaltic rocks?
Granitic rocks contain mostly quartz Granitic rocks contain mostly quartz and feldspar and thus are light-and feldspar and thus are light-colored. Basaltic rocks are rich in colored. Basaltic rocks are rich in iron and thus are dark-colored and iron and thus are dark-colored and more dense.more dense.
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