Transcript CLASSIFYING ROCKS - Dublin City Schools

CLASSIFYING ROCKS
P. 94-97
4.1
STUDYING ROCKS
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GEOLOGISTS LOOK AT SEVERAL
CHARACTERISTICS:
1. MINERAL COMPOSTITION
2. COLOR
3. TEXTURE
MINERAL COMPOSTITION
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ROCKS ARE MADE OF MIXTURES OF
MINERALS AND OTHER MATERIALS.
ABOUT 20 MINERALS MAKE UP MOST
OF THE EARTH’S CRUST. THESE
ARE KNOWN AS THE ROCKFORMING MINERALS.
COLOR
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A ROCKS’ COLOR PROVIDES CLUES AS
TO WHICH MINERALS ARE IN THE ROCK.
BASALT- A DARK COLORED ROCK THAT
IS LOW IN SILICA
GRANITE- A LIGHT COLORED ROCK HAS
HIGH AMOUNTS OF SILICA
REMEMBER COLOR DOESN’T TELL US
MUCH.
TEXTURE
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VERY USEFUL FOR IDENTIFYING.
GRAINS ( PARTICLES OF MINERALS)
GIVE ROCK THEIR TEXTURE OR
FEEL AND LOOK OF ROCK’S
SURFACE.
SMOOTH, GLASSY, CHALKY, ROUGH,
ALSO USE SIZE SHAPE AND
PATTERN OF GRAIN.
GRAIN SIZE
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IF A GRAIN IN A ROCK IS LARGE AND
EASY TO SEE IT IS CALLED COURSEGRAINED.
FINE-GRAINED IS SO HARD TO SEE
YOU WOULD NEED A MICROSCOPE.
\SOME HAVE NO VISIBLE GRAIN
EVEN UNDER A MICROSCOPE.
GRAIN SHAPE
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SOME GRAINS ARE ROUNDED AND
SOME ARE JAGGED.
GRAIN PATTERN
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SOME GRAINS FORM PATTERNS.
THEY CAN LIE IN FLAT LAYERS OR
STACKS . SOME SWIRL. SOME HAVE
DIFFERENT COLOR BANDS.
BANDED/ NONBANDED.
HOW ROCKS FORM
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WE WANT TO DETERMINE A ROCK
ORIGIN. WE CLASSIFY ROCKS INTO
CATEGORYS BASED ON WHERE
THEY FORMED.
IGNEOUS- MAGMA OR LAVA
METAMORPHIC-HEAT/PRESSURE
SEDIMENTARYCEMENTED/COMPACTED/BURIED
What are minerals
made up of and how do
they form?
3.2 p. 76-79
What are minerals made up of?
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Minerals are made up of elements or
compounds. Elements are atoms that
are all alike and have the same number
of protons, neutrons, and electrons.
Some minerals are compounds which
are combinations of different elements.
Reminder atoms have a nucleus and an
electron cloud.
The atom
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Protons and nuetrons are in the nucleus.
Electrons are in the electron cloud.
Mineral crystals
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I know that it is a stretch to get from
atoms to minerals but minerals are made
up of tiny atoms and when they bond
together- they form minerals. They also
form into 6 particular shapes or patterns.
Cubic, hexagonal, etc
Crystallization
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Crystal come in many sizes. Some are
geodes which are a rounded hollow rock
lined with mineral crystals.
They form when water seeps into the
rock and slowly evaporates leaving the
minerals behind to crystallize.
Crystallization is the process by which
atoms arrange themselves into a pattern.
2 ways minerals cystallize
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1. from molten material
2. from being dissolved in water
Minerals from magma and lava
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Magma-molten material inside the earth
Lava- magma that reaches the surface.
Anytime magma cools whether inside the
Earth or as lava, minerals crystallize. The
size of the crystals depend on the rate of
cooling.
Cools slow- large crystals
Cools fast- small crystals
Minerals from solutions
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A solution is a mixture in which one
substance is dissolved into another
substance.
Mineral crystals can form this way
underground or in bodies of water on
Earth’s surface either by evaporation or
from hot water solutions.
Evaporation
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When minerals are left behind after
water evaporates then crystals form
Examples:
Halite
Gypsum
calcite
Hot water solutions
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Magma heats water underground and
causes minerals to dissolve in the water,
when this water cools the elements and
compounds leave the solution and
crystallize.
Pure metals form veins or narrow
chambers or slabs of minerals. They
often form in cracks in the rock
surrounding it.