Download Rock Classification & Igneous Rocks

Earth Science Daily Challenge, 12/3
What do you already know about the
rock cycle and rock classification?
(Everyone knows SOMETHING
about it, so no “idk” today!)
Earth Science Daily Challenge, 12/4
How can you tell whether a
rock is igneous, sedimentary,
or metamorphic?
What kind of textures and/or
compositions are associated
with each rock type?
What is a ROCK?
• A rock is a solid mixture of minerals
and/or other materials.
How are rocks classified?
–Texture
• Grain size, shape, and layering
–Mineral Composition
• What is the rock made of?
–Origin
• How did the rock form?
SOME ROCK TEXTURES
• Coarse grained
• Grains are large enough to be seen by eye
• Fine grained
• Grains are small, need a microscope to see
• Glassy
• No grains, volcanic glass
• Prophyritic
• Few large grains in fine grained background
• Rounded or Angular
• Describes shape of grains
• Foliated
• Layering / banding in metamorphic rocks
ROCK COMPOSITION
• Iron-rich (mafic)
• Dark colors – black, dark grey, blue-grey
• Minerals like hornblende, biotite, olivine
• Silica-rich (felsic)
• Light colors – white, pink, tan
• Minerals like quartz, feldspar, muscovite
ROCK ORIGIN
• Igneous
• Cooling & crystallization of magma or lava
– Interlocking crystals of igneous minerals
• Sedimentary
• Lithification of sediments or dissolved solids
– Layers or masses of sedimentary minerals
• Metamorphic
• Heat & pressure recrystallize existing rocks
– Metamorphic minerals, may be foliated or not
Earth Science Daily Challenge, 12/8
Why do you think anyone
would care about studying
the rock cycle?
In other words, why is the
rock cycle important?
IGNEOUS ROCKS
• Igneous means “BORN OF FIRE”
• Formed by crystallization of magma or lava
• Often hard, durable, useful building stone
• Classified by…
–Composition (silica or iron rich = color)
–Texture (grain size & arrangement)
• Instrusive (magma cooled slowly)
–Coarse grained
• Extrusive (lava cooled quicky)
–Fine grained, Glassy, or Porphyritic
http://www.indiana.edu/~geol105/images/gaia_chapter_5/dike&sill.jpg
IGNEOUS FORMATIONS