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CLASSIFYING ROCKS

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classifying rocks p. 94-97 4.1 studying rocks geologists look at several characteristics: 1. mineral compostition 2. color 3. texture mineral compostition rocks are ... – PowerPoint PPT presentation

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Title: CLASSIFYING ROCKS


1
CLASSIFYING ROCKS
  • P. 94-97
  • 4.1

2
STUDYING ROCKS
  • GEOLOGISTS LOOK AT SEVERAL CHARACTERISTICS
  • 1. MINERAL COMPOSTITION
  • 2. COLOR
  • 3. TEXTURE

3
MINERAL COMPOSTITION
  • ROCKS ARE MADE OF MIXTURES OF MINERALS AND OTHER
    MATERIALS. ABOUT 20 MINERALS MAKE UP MOST OF THE
    EARTHS CRUST. THESE ARE KNOWN AS THE
    ROCK-FORMING MINERALS.

4
COLOR
  • 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 DOESNT TELL US MUCH.

5
TEXTURE
  • VERY USEFUL FOR IDENTIFYING.
  • GRAINS ( PARTICLES OF MINERALS) GIVE ROCK THEIR
    TEXTURE OR FEEL AND LOOK OF ROCKS SURFACE.
  • SMOOTH, GLASSY, CHALKY, ROUGH,
  • ALSO USE SIZE SHAPE AND PATTERN OF GRAIN.

6
GRAIN SIZE
  • IF A GRAIN IN A ROCK IS LARGE AND EASY TO SEE IT
    IS CALLED COURSE- GRAINED.
  • FINE-GRAINED IS SO HARD TO SEE YOU WOULD NEED A
    MICROSCOPE.
  • \SOME HAVE NO VISIBLE GRAIN EVEN UNDER A
    MICROSCOPE.

7
GRAIN SHAPE
  • SOME GRAINS ARE ROUNDED AND SOME ARE JAGGED.

8
GRAIN PATTERN
  • SOME GRAINS FORM PATTERNS.
  • THEY CAN LIE IN FLAT LAYERS OR STACKS . SOME
    SWIRL. SOME HAVE DIFFERENT COLOR BANDS.
  • BANDED/ NONBANDED.

9
HOW ROCKS FORM
  • WE WANT TO DETERMINE A ROCK ORIGIN. WE CLASSIFY
    ROCKS INTO CATEGORYS BASED ON WHERE THEY FORMED.
  • IGNEOUS- MAGMA OR LAVA
  • METAMORPHIC-HEAT/PRESSURE
  • SEDIMENTARY-CEMENTED/COMPACTED/BURIED

10
What are minerals made up of and how do they form?
  • 3.2 p. 76-79

11
What are minerals made up of?
  • 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.

12
The atom
  • Protons and nuetrons are in the nucleus.
  • Electrons are in the electron cloud.

13
Mineral crystals
  • 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

14
Crystallization
  • 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.

15
2 ways minerals cystallize
  • 1. from molten material
  • 2. from being dissolved in water

16
Minerals from magma and lava
  • 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

17
Minerals from solutions
  • 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 Earths surface either by
    evaporation or from hot water solutions.

18
Evaporation
  • When minerals are left behind after water
    evaporates then crystals form
  • Examples
  • Halite
  • Gypsum
  • calcite

19
Hot water solutions
  • 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.
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