Download Geosphere Unit

Geology Notes
Part 1
The Rock
Cycle
What is a rock?
• A rock is a mixture of such minerals,
rock fragments, volcanic glass,
organic matter, or other natural
materials.
There
is a hierarchy
to the
Atoms
make up elements.
elements of Geology
Elements combine to form
the natural compounds.
.
Natural compounds
and elements combine
to form minerals.
Minerals make up rocks.
Rocks make up the Earth.
How are rocks classified?
• first they are classified
into three groups based
on the way in the rocks
were formed
– Igneous, Sedimentary,
and Metamorphic
• then they are divided
further based on their
composition and texture
What are igneous rocks?
• a rock formed by
the cooling and
solidification of
magma or lava
What are some igneous rocks?
• granite, basalt,
obsidian, pumice,
gabbro, rhyolite
• they depend on the
composition of the
magma and the
amount of time it
takes to cool
PUMICE
What determines the size of
the crystals in igneous rocks?
• How fast it cools; the slower it cools, the
larger the crystals that form
Granite - Cool slowly;
thousands to millions
of years; course
grained
Rhyolite - Cool quick;
days to weeks; fine
grain or microscopic
grains
Obsidian - Cool VERY
quick; hours to days;
no crystals form
What is the difference between
intrusive and extrusive rocks?
• Intrusive are
formed when magma
cools slowly within
the Earth’s crust
• Extrusive form
when magma cools
fast at the surface
Extrusive rock
forms here
Geology Notes
Part 2
The Rock
Cycle
What are metamorphic rocks?
• Metamorphic rocks are
formed when other
kinds of rocks are
changed by great heat
and pressure inside the
earth.
• The word
"metamorphic" means
changed.
• Think of metamorphic
rocks as recycled
rocks.
What are some metamorphic rocks?
• Marble, quarttzite,
slate, schist, gneiss
• Limestone can be
changed to marble,
sandstone can be
changed into
quartzite, and
shale can be
changed to slate
What is the difference between
foliated and nonfoliated
metamorphic rocks?
• Foliation is a broad term
referring to the alignment
of sheet-like minerals.
(Slate, Gneiss)
• Non-foliated or granular
metamorphic rocks are
those which are composed
of equidimensional grains
such as quartz or calcite.
There is no preferred
orientation.
(Marble,Quartzite
What is the difference between
contact and regional metamorphism?
• Rocks that are in contact with hot
magma or lava often become
metamorphosed. This is called
contact metamorphism.
•Sometimes rocks are
metamorphosed over
large areas that are the
size of many states or
even several countries.
Explain how the texture of
metamorphic rock can indicate
whether it has experienced regional
or contact metamorphism.
• Foliation occurs when a
strong compressive force is
applied from one direction.
• Rocks that were subjected
to uniform pressure from all
sides, or those which lack
minerals with distinctive
growth habits, will not be
foliated.
Geology Notes
Part 3
The Rock
Cycle
What are sedimentary rocks?
• 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.
What are some sedimentary rocks?
• sandstone, limestone,
shale, and conglomerate
How are sedimentary rocks categorized?
• Like igneous and metamorphic rocks,
sedimentary rocks are classified by their
composition and by the manner in which they
formed.
• The three categories are:
– Clastic - are made up of pieces (clasts) of pre-existing
rocks that becomes compacted and cemented.
– Chemical - are formed by chemical precipitation, when
water traveling through rock dissolves some of the minerals,
eventually the minerals are redeposited when the water
evaporates away.
– Biologic/Organic - form from once-living organisms. They
may form from accumulated carbon-rich plant material or
from deposits of animal shells.
Explain how the size and shape of
grains in a sedimentary rock indicate
the environment of formation (including
climate) and deposition.
• The grain size depends on the energy of the environment
in which the sediment was deposited.
• The general shape of the grains will tell you about the
nature of the transporting medium.
• For example, a vigorous river transports much larger
grains than a gentle current in a lake, so the size of the
grains gives an indication of the strength of the currents
that could have transported and deposited the grains.
Animation
http://www.classzone.com/books/earth_science/terc/content/visualizations/es060
4/es0604page01.cfm?chapter_no=visualization
Geology Notes
Part 4
The Rock
Cycle
What are the processes that change
one kind of rock into another?
• When sediments from
any rock are compacted
or cemented, the
sediment becomes a
sedimentary rock
• a sedimentary rock can
change by heat and
pressure to form a
metamorphic rock
• any rock can be melted
and later cool to form
an igneous rock.