Download Classifying Igneous Rocks

Classifying Igneous Rocks
2017
IGNEOUS ROCKS
TEXTURE
Light-colored
(quartz
Dark-colored
olivine)
Coarse-grained
Granite
Diorite
Gabbro
Fine-grained
Rhyolite
Andesite
Basalt
little quartz
Obsidian
Glassy
Pumice
Porous
Scoria
orthoclase feldspar
plagioclase feldspar
***(quartz, olivine, orthoclase feldspar, and plagioclase feldspar are minerals)
Use the above chart to answer the following questions.
1.
What type of light-colored igneous rock with coarse-grains of quartz and orthoclase feldspar ?
___________________ granite _________________________________________________________________________
2.
What type of igneous rock is a fine-grained and dark-colored ? _________ basalt ___________________________
3.
What is the difference between diorite and andesite ?
_________________ diorite is coarse grained and andesite is fine grained ____________________________
4.
How are gabbro and granite different ?
__________________ gabbro is dark colored and granite is light colored _________________________
5.
Would it be easier to see individual minerals of granite or rhyolite ? ________ granite___________________________
6.
Which of the following igneous rocks would have the greatest amount of quartz:
rhyolite, diorite, or basalt ?
__________________________________________________________________________________________________
7.
What mineral other than plagioclase feldspar is very common in gabbro ?
_______ olivine___________________________
8.
Circle the following igneous rocks that are extrusive (cools quickly on the surface
creating fine-grained crystals).
basalt
diorite
rhyolite
granite
andesite
Classifying Igneous Rocks
2017
• Igneous rocks (most abundant type of rock) are formed from the cooling of molten rock material. The heat (approximately
1,400 ° C) that melts the rock does not come from the core of the earth, rather it generally comes from the radioactive decay of
elements in the mantle (60-200 km below the surface). This molten rock material that is found below the surface is referred to as
magma. As soon the molten rock material reaches the surface it is called lava.
• In situations which magma cools into igneous rocks, the resultant rocks are categorized as intrusive. Due to the slow cooling
within the earth the mineral crystals are able to grow relatively large, coarse-grained.
• When lava cools relatively quickly (volcanoes), the minerals form small crystals and the igneous rock is categorized as extrusive,
fine-grained. Generally speaking the crystals are too small to see with the naked eye.
• A sub-category of extrusive igneous rock are the glasses. These rocks cool so fast that no crystals form. Obsidian and pumice
are examples of volcanic glass.
• Additionally, you may further categorize igneous rocks by their chemical composition. Recollect the 2 types of crustal
material are basalt and granite.
• Mafic- basaltic magma is more dense, dark-colored, makes up ocean crust, and creates lava flows such as Hawaii.
• Felsic- granitic magma is less dense, light-colored, makes up continental crust, and creates pyroclastic eruptions.
• Look at the examples of igneous rocks. List them by the following categories: intrusive, extrusive, or
I-1 ________________________
I-2 _______________________
I-3 _______________________
I-4 ________________________
I-5 ________________________
I-6 ________________________
glass