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Rocks – Almost As Old As the Earth
“The Earth is made of rock, from the tallest mountains to the floor of the
deepest ocean. Thousands of different types of rocks and minerals have
been found on Earth. Most rocks at the Earth's surface are formed from only
eight elements (oxygen, silicon, aluminum, iron, magnesium, calcium,
potassium, and sodium), but these elements are combined in a number of
ways to make rocks that are very different.
Rocks are continually changing. Wind and water wear them down and carry
bits of rock away; the tiny particles accumulate in a lake or ocean and
harden into rock again. The oldest rock that has ever been found is more
than 3.9 billion years old. The Earth itself is at least 4.5 billion years old, but
rocks from the beginning of Earth's history have changed so much from their
original form that they have become new kinds of rock. By studying how
rocks form and change, scientists have built a solid understanding of the
Earth we live on and its long history.
Rock-forming and rock-destroying processes have been active for billions of
years. . . In a simple rock collection of a few dozen samples, one can
capture an enormous sweep of the history of our planet and the processes
that formed it.”
Image and text from: http://interactive2.usgs.gov/learningweb/explorer/topic_rocks.htm
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
Different Types of Rocks
“Geologists
classify rocks in three groups,
according to the major Earth processes
that formed them. The three rock groups
are igneous, sedimentary, and
metamorphic rocks. Anyone who
wishes to collect rocks should become
familiar with the characteristics of these
three rock groups. Knowing how a
geologist classifies rocks is important if
you want to transform a random group of
rock specimens into a true collection.”
Text from: http://interactive2.usgs.gov/learningweb/explorer/topic_rocks.htm ;
Image from: http://www.fi.edu/fellows/payton/rocks/create/index.html
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
Sedimentary Rock Formation
If you seeing this information from a PowerPoint
presentation or if you click on the web link listed below,
you will see this image as an animation that shows
sedimentary rock formation.
Image animation is from:
“For thousands, even millions of years,
little pieces of our earth have been
eroded--broken down and worn away
by wind and water. These little bits of
our earth are washed downstream
where they settle to the bottom of the
rivers, lakes, and oceans. Layer after
layer of eroded earth is deposited on
top of each. These layers are pressed
down more and more through time,
until the bottom layers slowly turn into
rock.”
http://www.fi.edu/fellows/payton/rocks/create/sediment.htm
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
Sedimentary Rock – Some
Examples
“Sandstone rocks are sedimentary rocks
made from small grains of the minerals
quartz and feldspar. They often form in
layers as seen in this picture. They are
often used as building stones.”
“Limestone rocks are sedimentary rocks
that are made from the mineral calcite
which came from the beds of evaporated
seas and lakes and from sea animal
shells. This rock is used in concrete and is
an excellent building stone for humid
regions.”
Image and text is from:
http://www.fi.edu/fellows/payton/rocks/create/sediment.htm
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
Sedimentary Rock – Some
Examples
“Shale rock is a type of sedimentary rock
formed from clay that is compacted
together by pressure. They are used to
make bricks and other material that is fired
in a kiln.”
“Conglomerate rocks are sedimentary
rocks. They are made up of large
sediments like sand and pebbles. The
sediment is so large that pressure alone
cannot hold the rock together; it is also
cemented together with dissolved
minerals.”
Image and text is from links to:
http://www.fi.edu/fellows/payton/rocks/create/sediment.htm
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
Sedimentary Rock – Some
Examples
“Gypsum rocks are sedimentary rocks
made up of sulfate mineral and formed as
the result of evaporating sea water in
massive prehistoric basins. It is very soft
and is used to make Plaster of Paris,
casts, molds, and wallboards.”
Image and text is from links to:
http://www.fi.edu/fellows/payton/rocks/create/sediment.htm
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
Sedimentary Rocks – More Detail
Bonus question: why do
you think these scientists
put a pen in the picture?
“Sedimentary rocks are formed at the surface of the Earth, either in
water or on land. They are layered accumulations of sediments:
fragments of rocks, minerals, or animal or plant material.
Temperatures and pressures are low at the Earth's surface, and
sedimentary rocks show this fact by their appearance and the
minerals they contain. Most sedimentary rocks become cemented
together by minerals and chemicals or are held together by electrical
attraction; some, however, remain loose and unconsolidated. The
layers are normally parallel or nearly parallel to the Earth's surface; if
they are at high angles to the surface or are twisted or broken, some
kind of Earth movement has occurred since the rock was formed.
Sedimentary rocks are forming around us all the time. Sand and
gravel on beaches or in river bars look like the sandstone and
conglomerate they will become. Compacted and dried mud flats
harden into shale. Scuba divers who have seen mud and shells
settling on the floors of lagoons find it easy to understand how
rocks form. limestone, and shale. These
rockssedimentary
include sandstone,
Common sedimentary
rocks often start as sediments carried in rivers and deposited in lakes and
oceans. When buried, the sediments lose water and become cemented to form
rock.”
Image and text from: http://interactive2.usgs.gov/learningweb/explorer/topic_rocks.htm
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
Igneous Rock Formation
If you seeing this information from a PowerPoint
presentation or if you click on the web link listed below,
you will see this image as an animation that shows
igneous rock formation.
Image animation and text is from:
“ Igneous rocks are called fire rocks
and are formed either underground or
above ground. Underground, they are
formed when the melted rock, called
magma, deep within the earth becomes
trapped in small pockets. As these
pockets of magma cool slowly
underground, the magma becomes
igneous rocks. Igneous rocks are also
formed when volcanoes erupt, causing
the magma to rise above the earth's
surface. When magma appears above
the earth, it is called lava. Igneous
rocks are formed as the lava cools
above ground.”
http://www.fi.edu/fellows/payton/rocks/create/igneous.htm
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
Igneous Rock – Some Examples
“Granite rocks are igneous rocks which
were formed by slowly cooling pockets of
magma that were trapped beneath the
earth's surface. Granite is used for long
lasting monuments and for trim and
decoration on buildings.”
“Scoria rocks are igneous rocks which
were formed when lava cooled quickly
above ground. You can see where little
pockets of air had been. Scoria is actually
a kind of glass and not a mixture of
minerals.”
Images and text are from links to:
http://www.fi.edu/fellows/payton/rocks/expert/igneous.htm
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
Igneous Rock – Some Examples
“Pumice rocks are igneous rocks which were
formed when lava cooled quickly above ground.
You can see where little pockets of air had been.
This rock is so light, that many pumice rocks will
actually float in water. Pumice is actually a kind of
glass and not a mixture of minerals. Because this
rock is so light, it is used quite often as a
decorative landscape stone. Ground to a powder,
it is used as an abrasive in polish compounds and
in Lava© soap.”
“Obsidian rocks are igneous rocks that form
when lava cools quickly above ground.
Obsidian is actually glass and not a mixture of
minerals. The edges of this rock are very
sharp.”
Images and text are from links to:
http://www.fi.edu/fellows/payton/rocks/expert/igneous.htm
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
Igneous Rocks – More Details
“Igneous rocks, also called volcanic rocks, are formed from
melted rock that has cooled and solidified. When rocks are
buried deep within the Earth, they melt because of the high
pressure and temperature; the molten rock (called magma)
can then flow upward or even be erupted from a volcano
onto the Earth's surface. When magma cools slowly, usually
at depths of thousands of feet, crystals grow from the molten
liquid, and a coarse-grained rock forms. When magma cools
rapidly, usually at or near the Earth's surface, the crystals
are extremely small, and a fine-grained rock results. A wide
variety of rocks are formed by different cooling rates and
different chemical compositions of the original magma.
Obsidian (volcanic glass), granite, basalt, and andesite
porphyry are four of the many types of igneous rock.
Common igneous (volcanic rocks) are basalt, andesite, and rhyolite. When
magmas crystallize deep underground they look different from volcanic rocks
because they cool more slowly and, therefore, have larger crystals. Igneous rocks
cooled beneath the Earth's surface are called intrusive rocks. The intrusive
equivalents of basalt, andesite, and rhyolite are gabbro, diorite, and granite,
respectively.”
Image and text from: http://interactive2.usgs.gov/learningweb/explorer/topic_rocks.htm
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
Metamorphic Rock Formation
If you seeing this information from a PowerPoint
presentation or if you click on the web link listed below,
you will see this image as an animation that shows
metamorphic rock formation.
“Metamorphic rocks are rocks that
have "morphed" into another kind of
rock. These rocks were once igneous
or sedimentary rocks. How do
sedimentary and igneous rocks
change? The rocks are under tons and
tons of pressure, which fosters heat
build up, and this causes them to
change. If you exam metamorphic rock
samples closely, you'll discover how
flattened some of the grains in the rock
are.”
Image animation and text is from:
http://www.fi.edu/fellows/payton/rocks/create/metamorph.htm
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
Metamorphic Rock – Some
Examples
“Schist rocks are metamorphic. These rocks
can be formed from basalt, an igneous rock;
shale, a sedimentary rock; or slate, a
metamorphic rock. Through tremendous heat
and pressure, these rocks were transformed
into this new kind of rock.”
“Gneiss rocks are metamorphic. These rocks
may have been granite, which is an igneous
rock, but heat and pressure changed it. You
can see how the mineral grains in the rock
were flattened through tremendous heat and
pressure and are arranged in alternating
patterns.”
Image and text is a link from:
http://www.fi.edu/fellows/payton/rocks/create/metamorph.htm
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
Metamorphic Rocks – More Details
“Sometimes sedimentary and igneous rocks are subjected
to pressures so intense or heat so high that they are
completely changed. They become metamorphic rocks,
which form while deeply buried within the Earth's crust. The
process of metamorphism does not melt the rocks, but
instead transforms them into denser, more compact rocks.
New minerals are created either by rearrangement of
mineral components or by reactions with fluids that enter the
rocks. Some kinds of metamorphic rocks--granite gneiss
and biotite schist are two examples--are strongly banded or
foliated. (Foliated means the parallel arrangement of certain
mineral grains that gives the rock a striped appearance.)
Pressure or temperature can even change previously
metamorphosed rocks into new types.
Common metamorphic rocks include schist, marble, and gneiss. Sedimentary
rock shale (formed mostly of clay sediments) when buried and heated to high
temperatures (300-500°C) becomes transformed or metamorphosed into schist.”
Image and text from: http://interactive2.usgs.gov/learningweb/explorer/topic_rocks.htm
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
What is the Rock Cycle?
“Like most Earth materials, rocks are created and destroyed in cycles. The rock
cycle is a model that describes the formation, breakdown, and reformation of a
rock as a result of sedimentary, igneous, and metamorphic processes. All rocks
are made up of minerals. A mineral is defined as a naturally occurring, crystalline
solid of definite chemical composition and a characteristic crystal structure. A
rock is any naturally formed, nonliving, firm, and coherent aggregate mass of
solid matter that constitutes part of a planet.”
Image and text from:
http://imnh.isu.edu/digitalatlas/geo/basics/diagrams.htm
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
NY State Geologic Map
- This map shows the type of rocks found in the different regions
of New York; although the information is complex, you can easily
see the patterns where various rocks are found. What do you
think these patterns tell us about the geographic features of New
York? Do any patterns appear familiar? You can go to the link
below if you are interested is seeing the interesting details about
New York and its geologic history .
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
http://geology.about.com/library/bl/maps/newyorkmapmid.jpg?once=true&
Lesson on the Rocks & Rock
Formation
• The following information has been compiled from a
number of government and education web sites (the
links are shown on the pages)
• This information is provided in print format for students
who can not access the web sites directly
• This information will serve as background text to several
school lessons
• Students should be encouraged to access the web sites
themselves (links are provided on the pages) so they
can explore more about these topics; a more
comprehensive list of web sites is available through
http://www.ils-courses.net/rocks
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available
More Information on Geology
• See http://www.ils-courses.net/rocks for
more links to geology information and a
companion web site that is associated with
Dr. O’Connor’s work on this geology unit
• You can reach Dr. Eileen O’Connor at:
[email protected]
Assembled from web sources by E. O’Connor, Ph.D. / Instructional supplement available