Download IGNEOUS ROCKS

IGNEOUS ROCKS
Igneous rocks are one of three main categories of rock that
include sedimentary and metamorphic. The first rocks on Earth
were igneous rocks. The word igneous comes to us from the
Latin‘ignis’ meaning fire. Igneous rocks are geologically
important because their minerals and chemistry give us
information about the composition of the Earth’s mantle from
which some igneous rocks originate. Their features are
usually associated with specific tectonic environments and
they may also host important mineral deposits including
tungsten,chromium, platinum, tin and uranium.
Mineral Composition of Igneous Rocks
Feldspars, quartz, feldspathoids, olivines, pyroxenes, micas
and amphiboles are important minerals in the formation of all
types of igneous rock. Felsic rock has a high silicon content
including quartz and feldspar. Felsic rocks are usually light
colored and have a low density. Mafic rock has less silicon
content and more mafic minerals such as pyroxenes and olivines.
How Igenous Rocks Form
Igneous rock is formed from the cooling and solidification of
hot molten rock. Where the rock cools and solidifies and how
fast it cools are the criteria that is used to classify and
identify kinds of igneous rock. Magma that form intrusive
igneous rocks tend to cool more slowly forming coarse textured
rock, while extrusive igneous rocks formed from lava tend to
cool more quickly forming fine textured rocks.
Intrusive Igneous Rock
Intrusive igenous rock is formed from magma that cools and
solidifies within Earth’s crust. Plutonic is a term that is
also used to identify intrusive rocks. As magma wells upwards,
it fills crevices and eventually hardens, only becoming visible
when the soil above it has eroded away. Because magma cools
slowly, the texture of intrusive rocks is often coarse or
phaneritic. The central cores of major mountain
ranges consist of intrusive igneous rocksusually granite. Intrusive igneous rocks can also
be classified according to the size and shape of
the formations into which they intrude. These
formations include batholiths, stocks,
laccoliths, dikes and sills. Examples of
intrusive igneous rocks include Granite, Gabbro, Diorite and
Peridotite.
Extrusive Igneous Rocks
Extrusive igeneous rock is formed from lava
released by volcanoes that cools and soldifies
on the surface of the Earth. Volcanic is a term
that is also used to identify extrusive
igneous rocks. Because lava cools and solidifies
more rapidly on the surface of the Earth, many
extrusive igneous rocks are fine grained and
textured. Examples of extrusive igneous rocks include
Obsidian, Basalt, Rhyolite, Andesite and Komatilite
The rock to the left is an example of an intrusive rock. Note
the coarse grains indicating the magma cooled slowly. The rock
on the right Obsidian is extrusive with much finer grains.
FEATURED PINTEREST PINS
https://www.pinterest.com/pin/23573598020685896/
Nice diagram showing igneous rock classification
https://www.pinterest.com/pin/560205641129195833/
Relationship between igneous rocks and tectonic plates
https://www.pinterest.com/pin/AWRVwyxPXhytE31PpWtsNNjSmPdFR0OitwMzZLyaRMeqk6q9r1Njb4/
Simplified volcanic rock identification chart
https://www.pinterest.com/pin/503629170808679522/
Textures of igneous rocks
https://www.pinterest.com/pin/5770305750621369/
Using food to demonstrate the three different kinds of rocks
https://www.pinterest.com/pin/86131411600994452/
Using Crayons to teach the rock cycle
https://www.pinterest.com/pin/445997169329475882/
Sample Igneous rocks
RECOMMENDED INTERNET RESOURCES
http://www.usgs.gov/faq/categories/9819/2756
USGS website in an FAQ format that describes the types and
classification of igneous rocks.
http://jersey.uoregon.edu/~mstrick/AskGeoMan/geoQuerry14.html
Geo-Man description of igneous rock texture and composition.
http://www.pitt.edu/~cejones/GeoImages/2IgneousRocks/IgneousCompositions.html
Brief summary of how igneous rocks are classified according to
mineral type.
http://www.arch.dcr.state.nc.us/ncarch/geoarcheo/igneousA.htm
Read the description on the page and then click the flow chart
at the bottom of the page.
http://volcano.oregonstate.edu/igneous-rocks-lesson-12
Oregon State University website that provides a great
description of types of igneous rocks as well as illustrations
showing the role of tectonic plate movements in igneous rock
formation.
http://geology.com/rocks/igneous-rocks.shtml
Includes images of igneous rocks
http://www.mineralogy4kids.org/rock-cycle/extrusive-igneousrocks
Very brief, but includes some very high quality images of
different types of igneous rock
https://www.msnucleus.org/membership/html/k-6/rc/index.html
A nice assembly of different aspects of the study of rocks and
minerals as well as fossils. Includes references to some
commercial catalog items for purchase, but you can easily
adapt the activities without purchasing the items
http://www.physicalgeography.net/fundamentals/10e.html
Always one of my favorite websites for Earth Science, this
website describes types and characteristics of igneous rocks
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Mark A. Van Hecke
Instructional Design Consultant
www.vanheckescience.com
[email protected]