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Rocks and the Rock Cycle


The Rock Cycle is a group of changes, this change does not necessarily have to be a chemical change. Igneous rock can change into sedimentary rock or into metamorphic ... – PowerPoint PPT presentation

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Title: Rocks and the Rock Cycle

Rocks And The Rock Cycle
Why Are Rocks Important To Us?
Buildings Roads Bridges Concrete Extract minerals
like iron (Fe) to make steel Toothpaste Salt San
dpaper Decorations Jewelry
1. Why is it important to have a basic
understanding of the rock cycle?
Rocks contain clues about the environment.
Helps us understand the formation of the earth.
2. Rock
Any solid mass of minerals or mineral-like matter
3. Do most rocks occur as one mineral or as a
mixture of minerals?
4. Some rocks are made of non-mineral material,
can you name one?
Coal - begins as layers of plant matter
accumulate at the bottom of a body of water. For
the process to continue the plant matter must be
protected from biodegradation and oxidization,
usually by mud or acidic water. This trapped
atmospheric carbon in the ground in immense peat
bogs that eventually were covered over and deeply
buried by sediments under which they
metamorphosed into coal. Over time, the chemical
and physical properties of the plant remains
(believed to mainly have been fern-like species
antedating more modern plant and tree species)
were changed by geological action to create a
solid material.
Coal, a fossil fuel, is the largest source of
energy for the generation of electricity
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5. Explain the rock cycle.
A continuous process that causes rock to change
from one form to another
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The Rock Cycle
  • The Rock Cycle is a group of changes, this change
    does not necessarily have to be a chemical
  • Igneous rock can change into sedimentary rock or
    into metamorphic rock.
  • Sedimentary rock can change into metamorphic rock
    or into igneous rock.
  • Metamorphic rock can change into igneous or
    sedimentary rock.
  • Almost all of rock today that we have on earth is
    made up of all the same stuff as the rocks that
    dinosaurs and other ancient life forms walked,
    crawled, or swam over
  • While the stuff that rocks are made of has stayed
    the same, the rocks themselves, have not
  • Over time rocks are recycled into other rocks
  • Moving tectonic plates are responsible for
    destroying and forming many types of rocks

6. List the 3 types of rocks
Igneous Metamorphic Sedimentary
7. Igneous Rocks
  • Igneous rock forms when magma cools and makes
  • Magma is a hot liquid made of melted minerals.
    When magma pours onto the earths surface it is
    called lava. The minerals can form crystals when
    they cool.
  • Igneous rock can form underground, where the
    magma cools slowly. Or, igneous rock can form
    above ground, where the magma cools quickly.
  • The crystals grow together and form one igneous

8. What kind of igneous rocks form when molten
lava cools and hardens?
Extrusive forced out while molten through
cracks in the earth's surface
9. What is the Latin word that the word igneous
comes from and what does it mean?
ignis fire
10. Intrusive Igneous Rocks
Form from magma below the earths surface
11. Extrusive Igneous Rocks
Formed by lava on the Earths surface
12. What is the difference between magma and
Lava molten rock flowing on the earths surface
Magma molten rock below the earths surface
13. What are the 8 elements that make up magma?
Silicon, oxygen, aluminum, iron, calcium, sodium,
potassium, magnesium
Look at the granite rock (A on age 71) and the
rhyolite rock (B on page 71)
14. In what ways are the two rocks similar?
Both are from melted rock Their composition is
the same
15. In what ways are the two rocks different?
Granite coarse texture, made from magma
Rhyolite fine texture, made from lava
16. What causes the two rocks to be different?
Granite Slow cooling below the earths surface
Rhyolite Quick cooling on the earths surface
17. Why do you think some rocks are heavier
than others?
Some are denser less air space between particles
Which rock would have greater density?
Classifying Rocks
Rocks can be classified, or put into groups with
similar characteristics, by looking at the rocks
texture, mineral composition, and color.
18. What is texture?
The size, shape, and pattern of the rocks grain
19. Composition (whats it made of?)
The minerals that make up the different parts of
a rock
ADD Rock Color
The apparent color of the rock, on the inside and
the outside
20. Slow cooling magma will form rocks with
a a. coarse grained texture. b. fine grained
texture. c. glassy texture. d. porphyritic
  • Rapid cooling magma will form rocks with a
  • a. coarse grained texture.
  • b. fine grained texture.
  • c. glassy texture.
  • d. porphyritic texture.

22. When lava spews onto the earths surface
rocks will form with a a. coarse grained
texture. b. fine grained texture. c. glassy
texture. d. porphyritic texture.
23. Magma that is located deep within the earth
may take tens of thousands of years to
harden. The rocks that form in this case will
have a a. coarse grained texture. b. fine
grained texture. c. glassy texture. d.
porphyritic texture.
24. Which 2 minerals are granitic rocks
composed of?
Quartz Feldspar
25. Which 2 minerals are basaltic rocks
composed of?
Magnesium Iron
  • Metamorphic rocks are rocks that have "morphed"
    into another kind of rock.
  • These rocks were once igneous or sedimentary
  • 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.

The Rock Divisions
  • Rock divisions occur in three major families
    based on how they formed igneous, sedimentary,
    and metamorphic.
  • Each group contains a collection of rock types
    that differ from each other on the basis of the
    size, shape, and arrangement of mineral grains.
  • Just remember 3 types of rocks3 divisions.
    (igneous, sedimentary, and metamorphic)

Classifying Rocks
  • When classifying a rock sample geologists observe
    the rocks color and texture and determine its
    mineral composition.
  • Texture the size, shape, and pattern of the
    rocks grain.
  • Color the apparent color of the rock, on the
    inside and the outside.
  • Mineral composition The minerals that make up
    the different parts of a rock.

Texture Grain Size
  • Often, the grains in a rock are large and easy to
  • Such rocks are said to be coarse-grained. In
    other rocks, the grains are so small that they
    can only be seen with a microscope.
  • These rocks are said to be fine-grained.
  • Notice the difference in texture between the
    fine-grained slate and the coarse-grained diorite
    to the right.

Texture Grain Shape
  • The grains in a rock vary widely in shape
  • Some grains look like tiny particles of fine sand
  • Others look like small seeds or exploding stars
  • In some rocks, such as granite, the grain results
    from the shapes of the crystals that form the
  • In other rocks, the grain shape results from
    fragments of other rock
  • These fragments can be smooth and rounded, like
    the fragments in conglomerate, or they can be
    jagged, like the fragments in breccia
  • You can compare conglomerate and breccia one the
    next slide

Texture Grain Pattern
  • The grains in a rock often form patterns. Some
    grains lie in flat layers that look like a stack
    of pancakes.
  • Other grains form wavy, swirling patterns. Some
    rocks have grains that look like rows of
    multicolored beads, as in the sample of gneiss
    shown above.
  • Other rocks, in contrast, have grains that occur
    randomly throughout the rock.

Different Types of Texture
Fine-Grained, Coarse-Grained, Rounded Grain,
Jagged Grain, Nonbanded, Banded
2 Types of Igneous Rocks
  • INTRUSIVE IGNEOUS ROCKS When igneous rocks are
    formed by magma that cools BENEATH Earths
    surface, they are called intrusive igneous rocks
  • EXTUSIVE IGNEOUS ROCKS When igneous rocks are
    formed by LAVA ON Earths surface, they are
    called extrusive igneous rocks

  • The process by which sediment becomes sedimentary
  • 1st step erosion
  • 2nd step deposition
  • 3rd step compaction
  • 4th step cementation

Sedimentary Rocks Erosion
  • Destructive forces are constantly breaking up and
    wearing away all the rocks on Earths surface
  • The forces include heat and cold, rain, waves,
    and grinding ice
  • Erosion occurs when running water or wind loosens
    and carry away the fragments of rock.

Sedimentary Rocks Deposition
  •  Eventually, the moving water or wind slows and
    deposits the sediment.
  • If water is carrying the sediment, rock fragments
    and other materials sink to the bottom of a lake
    or ocean.
  • Deposition is the process by which sediment
    settles out of the water or wind carrying it.
  • After sediment has been deposited, the processes
    of compaction and cementation change the sediment
    into sedimentary rock.
  • In addition to particles of rock, sediment may
    include shells, bones, leaves, stems, and other
    remains of living things.
  • Over time, any remains of living things in the
    sediment may slowly harden and change into
    fossils trapped in the rock.

Sedimentary Rocks Compaction
  •  At first the sediments fit together loosely. But
    gradually, over millions of years, thick layers
    of sediment build up.
  • These layers are heavy and press down on the
    layers beneath them.
  • Then compaction occurs.
  • Compaction is the process that presses sediments
  • Year after year more sediment falls on top,
    creating new layers.
  • The weight of the layers further compacts the
    sediments, squeezing them tightly together.
  • The layers often remain visible in the
    sedimentary rock.

Sedimentary Rocks Cementation
  •  While compaction is taking place, the minerals
    in the rock slowly dissolve in the water.
  • The dissolved minerals seep into the spaces
    between particles of sediment.
  • Cementation is the process in which dissolved
    minerals crystallize and glue particles of
    sediment together.
  • It often takes millions of years for compaction
    and cementation to transform loose sediments into
    solid sedimentary rock.

Sedimentary Transformations
  • Point A water or wind deposits sediments
  • Point B The heavy sediments press down on the
    layers beneath
  • Point C Dissolved minerals flow between the
    particles and cement them together

Metamorphic Rock Pictures
Granite, Gneiss, Shale, Slate, Sandstone, and
Quartzite are good examples of metamorphic rocks.
Bet Cha Werent Expecting A.POP QUIZ!!!!!
  • What are the three types of rock?
  • Which type of rock has been formed by magma or
  • What do we classify rocks by?
  • How do sedimentary rocks form (in order)?
  • Metamorphic rocks are rocks that have
  • ?(fill in the blank)
  • What is the process of sediments forming a
    sedimentary rock?
  • What does ignis mean in the word igneous?

Answers are on next slide!
  1. Igneous, Sedimentary, and Metamorphic
  2. Igneous
  3. Texture, Color, and Mineral Composition
  4. Erosion, Deposition, Compaction, Cementation
  5. Morphed
  6. Lithification
  7. ignis means fire

  • Earth Science Textbook
  • http//

Sedimentary Rocks
  • Sedimentary rocks form from particles deposited
    by water and wind
  • If you have ever walked along a beach (which I am
    sure you have) you may have noticed tiny sand
    grains, mud, and pebbles.
  • These are some sediments that eventually form
    into sedimentary rocks
  • Sedimentary Rocks can form in 4 ways by
  • Erosion
  • Deposition
  • Compaction
  • Cementation
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