Rocks

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Rocks
Rocks! What makes up Earths Crust
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Three types of rocks
Sedimentary

• Igneous

• Metamorphic

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What is a rock?

• A rock is a solid that forms in nature. It
  may have one or more types of minerals within it
• (or no minerals at all).

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Some rocks have minerals, some dont

• Minerals are clearly visible in some igneous
  rocks like..

• There are no mineral
• crystals in obsidian.

Diorite
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What is the rock cycle?

• Natural processes
• that
• Forms
• Changes
• Breaks down rocks
• Rock is
• reformed
• into another
• type of rock.

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The rock cycle in action

• The rock cycle
• shows the
• three types of
• rocks.
• Igneous
• Metamorphic
• Sedimentary
• ? Listen and watch how the processes formed the
  three types of rocks.

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Igneous Rock

• Forms when molten rock cools and becomes a solid.
• Igneous rocks may form inside Earth or on Earths
  surface.

• ?Intrusive-forms when magma cools within the
  Earth.
• ?Extrusive-forms when lava cools on the surface.

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What is a rocks texture?

• Texture refers
• to the size of
• the mineral crystals
• coarse, fine, glassy

Coarse
Pumice
Glassy
Fine
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Textures of Intrusive Igneous Rock
Intrusive Rocks

• The size of mineral crystals depends on how
  quickly the magma or lava cooled.
• The high temperatures of the interior of the
  Earth causes magma to cool slowly.
• Slow cooling allows large crystals to form.

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How are we able to see intrusive rocks?

• Ship Rock formed 30 million years ago.
• Magma cooled to form intrusive rock.
• Intrusive igneous rock
• has been left as weaker rock (like
  sedimentary) has worn away
• due to weathering erosion.

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Textures of Extrusive Igneous Rock

• The surface of Earth is much cooler than the
  interior, causing lava to cool quickly.
• There is no time for large mineral crystals to
  form.

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Composition of Igneous Rocks

• Most igneous rocks are made up of silicate
  materials
• The color tells you how much silica the rock has.

• High levels of silica will be lighter in color.
• Low levels of silica will be darker in color.

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What type of rock was carved to create Mount
Rushmore?
Igneous!
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Interesting Rock Formations
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1
4
2
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• Which of these is a rock?

• A. halite B. granite
• C. mica D. quartz

Answer B. granite
Which is formed from cooling magma?
A. metamorphic B. igneous C. sedimentary D.
sandstone
Answer B. igneous
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Sedimentary Rocks something that settles

• Small pieces of rock turn into pebbles, gravel,
  sand, clay, and plant animal matter. They
  tumble down rivers and streams.
• These pieces settle in a new place and begin to
  pile up and the sediments form flat layers.

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Sediments harden into rock in two ways.

• Compaction- layer after layer of sediments are
  deposited, they are pressed together tightly to
  form rock.
• Cementation- sediments are held together by
  minerals that have crystallized between them
  (acting as cement).

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Sedimentary rocks may be rich in.

• Fossils- Remains or trace of an organism from
  long ago.
• Coal-Made up of the remains of dead plants. The
  coal we use today formed millions of years ago in
  swamps.
• Limestone-made of carbonate minerals (calcite)
  from seashells that settle on the bottom of the
  ocean.

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COAL Natures rock..
Coal is made from dead plants and over time
pressed into the Earth.
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Sedimentary Rock tells a story about Earths past

• These rocks are laid down in layers with the
  oldest on the bottom.

Do you remember what rock layers are called?
Law of Superposition or stratification!
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Do you remember?

• What layer of rock is the Oldest?

Youngest
Oldest
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Metamorphic RockChanged Rock
Sedimentary
Metamorphic
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Composition and Texture a way to identify
metamorphic rock

• When mineral grains line up in parallel layers,
  the metamorphic rock is said to have a Foliated
  texture.

Slate
Gneiss
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Non Foliated Metamorphic Rock
When a metamorphic rock does not have foliation
it typically has only one mineral, therefore no
parallel banding patterns.

• Typically made up of one type of mineral so
  different minerals can not line up in bands.

• Marble formed from limestone

Quartzite forms from Sandstone
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Metamorphic Rocks are formed when



Metamorphic Rock
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How much of Earths Crust is made of each type of
rock?
Surface 75 Sedimentary Rock Entire Crust 95
Igneous and Metamorphic Rock
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• What type of rock is the most common
• on the surface of Earths crust?

A. metamorphic B. igneous C. sedimentary D.
sandstone
Answer C. sedimentary
95 of Earths entire crust consist of what
type(s) of rock?

• A. metamorphic B. sedimentary
• C. igneous D. igneous and metamorphic

Answer D igneous and metamorphic