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Igneous Rocks

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Igneous Rocks Hot rocks/Fire Rocks Igneous Rock Igneous rocks form when: molten rock cools and solidifies. Igneous Rocks Molten rock is called magma when it is below ... – PowerPoint PPT presentation

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Title: Igneous Rocks


1
Igneous Rocks
  • Hot rocks/Fire Rocks

2
Igneous Rock
  • Igneous rocks form when molten rock cools and
    solidifies.

3
Igneous Rocks
  • Molten rock is called magma when it is below the
    Earths surface and lava when it is above.

4
Igneous Rocks
  • Remember
  • Rate of cooling affects crystal size
  • Fast cooling small crystals
  • Slow cooling large crystals

5
Crystal size
Magma (below)
when molten rock cools and solidifies
Lava (above)
6
Igneous Rock classification
  • Igneous rocks are classified two ways
  • Where they were formed
  • What they are made from (mineral composition)

7
Part 1
  • Classifying igneous rocks by where they are
    formed.

8
Igneous Rocks - Classification
  • Igneous rocks that form below the Earths surface
    are called intrusive igneous rocks (or plutonic).

9
Igneous Rocks - classification
  • The word plutonic comes from Pluto, the name
    for the Roman god of the underworld.

10
Igneous Rocks - Classification
  • They form when magma enters a pocket or chamber
    underground that is relatively cool and
    solidifies into crystals as it cools very slowly.

11
Intrusive Igneous Rock
  • Most intrusive rocks have large, well formed
    crystals. The mineral crystals within them are
    large enough to see without a microscope.

12
Igneous Rocks - Classification
  • The more slowly molten rock cools within the
    Earth, the larger the igneous rock crystals will
    be.

13
Crystal size
magma
Intrusive
slowly
Magma (below)
when molten rock cools and solidifies
large
Lava (above)
14
Intrusive Igneous Rocks - examples
  • Gabbro

15
Intrusive Igneous Rocks - examples
  • Diorite

16
Intrusive Igneous Rocks - examples
  • Granite

17
Crystal size
magma
Intrusive
slowly
Magma (below)
when molten rock cools and solidifies
large
Lava (above)
Granite, gabbro, diorite
18
Extrusive Igneous Rocks
  • Extrusive igneous rocks, or volcanic rocks, form
    when magma makes its way to Earth's surface. The
    molten rock erupts or flows above the surface as
    lava, and then cools RAPIDLY forming rock.

19
Extrusive Igneous Rocks
  • Most extrusive (volcanic) rocks have small
    crystals.

20
Extrusive Igneous rocks - examples
  • Basalt

21
Extrusive Igneous rocks - examples
  • Andesite

22
Extrusive Igneous rocks - examples
  • Rhyolite

23
Lava
Crystal size
Quickly
Small or not visible
Extrusive
Basalt, ryolite, andesite
magma
Intrusive
slowly
Magma (below)
when molten rock cools and solidifies
large
Lava (above)
Granite, gabbro, diorite
24
Volcanic Glass
  • Pumice, obsidian, and scoria are examples of
    volcanic glass.
  • These rocks cooled so quickly that few or no
    mineral grains formed.
  • Most of the atoms in these rocks are not arranged
    in orderly patterns, and few crystals are
    present.

25
Glassy Igneous Rocks
Glassy Igneous Rocks cool so rapidly, that atoms
dont have enough time to get together, bond and
form crystals. To cool this quickly the rocks
MUST be extrusive.
  • Pumice (left)
  • Scoria (bottom left)
  • Obsidian (bottom)
  • Note gasses in the lava can cause fine holes
    called vesicles as seen in the pumice and scoria.

26
Part 2
  • Classifying by mineral composition

27
Composition Magma types
  • A way to further classify these rocks is by the
    magma from which they form. An igneous rock can
    form from, granitic, andesitic, or basaltic
    magma.

28
Composition - Properties
  • Magma composition determines the physical
    chemical properties of an igneous rock

29
Lava
Crystal size
Slowly
granitic
Small or not visible
Physical chemical properties
Extrusive
Basalt, ryolite, andesite
andesitic
magma
Intrusive
slowly
Magma (below)
basaltic
when molten rock cools and solidifies
large
Lava (above)
Granite, gabbro, diorite
SiO2 Silicon Fe Iron Mg Magnesium
30
Basaltic Igneous Rocks
  • They form from magma that is rich in iron (Fe)
    and magnesium (Mg) and LOW in silica (SiO2.)

31
Basaltic Igneous Rocks
  • The presence of iron (Fe) and magnesium (Mg) in
    basalt gives basalt its dark color.
  • Basalt rocks have a high density

32
Basaltic Igneous Rocks
  • Basaltic lava is fluid and flows freely from
    volcanoes in Hawaii, such as Kilauea.
  • Basalt is the most common rock type in the
    Earth's crust (the outer 10 to 50 km).
  • Makes up the Oceanic Crust

33
Lava
Crystal size
Slowly
granitic
Small or not visible
Physical chemical properties
Extrusive
basalt, ryolite, andesite
andesitic
magma
Intrusive
Rich in Fe Mg poor in SiO2
slowly
Magma (below)
basaltic
Dense dark colored
when molten rock cools and solidifies
large
Lava (above)
Ocean floor Hawaii
Granite, gabbro, diorite
34
Granitic Rocks
  • Granitic igneous rocks are light-colored rocks of
    lower density than basaltic rocks.

35
Granitic Rocks
  • Granitic rocks are coarse-grained
  • Granitic magma is thick and stiff, high silica
    content, lesser amounts of Fe and Mg.

36
Granitic Rocks
  • It is the most common rock type on the
    continental land masses.
  • Yosemite Valley in the Sierra Nevada Mtn. range
    and Mt. Rushmore are two notable examples of
    granitic rocks
  • Makes up the continental crust

37
Lava
High SiO2 Low Fe Mg
Crystal size
Slowly
granitic
Light colored, less dense
Small or not visible
On the continents
Physical chemical properties
Extrusive
basalt, ryolite, andesite
andesitic
magma
Intrusive
Rich in Fe Mg poor in SiO2
slowly
Magma (below)
basaltic
Dense dark colored
when molten rock cools and solidifies
large
Lava (above)
Ocean floor Hawaii
Granite, gabbro, diorite
38
Andesitic Rocks
  • Andesitic igneous rocks have mineral compositions
    between those of basaltic and granitic rocks.
  • Color tends to be between dark and light.
  • Medium density

39
Andesitic Rocks
  • Many volcanoes around the rim of the Pacific
    Ocean formed from andesitic magmas.

40
Andesitic Rocks
  • Like volcanoes that erupt granitic magma, these
    volcanoes also can erupt violently.
  • Rocks made from andesite tend to be fine-grained.

41
Lava
High SiO2 Low Fe Mg
Crystal size
Slowly
granitic
Light colored, less dense
Small or not visible
On the continents
Physical chemical properties
b/t basaltic granitic
Extrusive
basalt, ryolite, andesite
andesitic
Grey, medium
magma
Pacific Rim
Intrusive
Rich in Fe Mg poor in SiO2
slowly
Magma (below)
basaltic
Dense dark colored
when molten rock cools and solidifies
large
Lava (above)
Ocean floor Hawaii
Granite, gabbro, diorite
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