GEOLOGY MACC Bill Palmer
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GEOLOGY MACC Bill Palmer Lecture 4 Rocks
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GEOLOGY MACC Bill Palmer. Lecture 4 Rocks. What are Rocks?. Rocks are solid materials that comprise nearly all of the earth (and moon and planets). Rocks are almost always aggregates of minerals. (This is why we study minerals first). What is the Rock Cycle?. - PowerPoint PPT Presentation
Transcript of GEOLOGY MACC Bill Palmer
GEOLOGYMACC
Bill Palmer
Lecture 4Rocks
What are Rocks?Rocks are solid materials that comprise nearly all of
the earth (and moon and planets).
Rocks are almost always aggregates of minerals.(This is why we study minerals first).
What is the Rock Cycle? The rock cycle explains how all rocks can be
formed, deformed transformed, destroyed, and reformed as a result of natural processes.
Rock CycleMaterials for forming rocks comes from:
1) the Earth’s mantle (molten rock is magma when in the ground and lava when it erupts on the surface)
2) Space (meteorites)3) Organisms (plants and animals) 4) Fragmentation and decay of other rocks and minerals
Rock CycleThere are three main rock groups:
1) IGNEOUS ROCKS –Form when magma or lava cool.
2) SEDIMENTARY ROCKS- Form when chemical residues and fragments of plants, animals, crystals, or rocks, or sand are compressed and cemented together. Also form from chemical precipitation.
3) METAMORPHIC ROCKS- Form when other rocks are changed by heat, pressure, or hot fluids.
The Rock Cycle
Rock Properties 1. General form-smooth, rough, irregular 2. Color-light, dark, 3. Grains-sand, gravel, crystals, fossils, fragments 4. Shape-teardrop, icicle, smooth, sphere
Rock Properties 5. Texture is very important-
GlassyFine-grained , <1mmCoarse-grained, >1mmVesicular-bubblesFoliated-layersClastic-”clasts” of plants, animals, minerals
Igneous Rocks Intrusive Igneous Rocks-Magma is the source
and the rocks cool slowly beneath the ground and form large crystals.
Extrusive Igneous Rocks-Lava is the source and the rocks cool quickly above the ground and form small crystals.
INTRUSIVE STRUCTURES1. Batholith-Massive, no “bottom” 2. Sills-Sheet-like between layers of other rocks3. Laccolith- “Blister-like”4. Pipe-vertical tube5. Dikes-Layers vertical to rock
1. Radial2. Sheet3. Ring
EXTRUSIVE Lava Flows Pyroclastic deposits (fire fragments)
How to Analyze Igneous Rocks STEP 1 and 2-Study the Color and Mineral
CompositionLight- Felsic Minerals (feldspar)
Quartz (gray, white)Plagioclase Feldspar (white)Potassium Feldspar (pink)Muscovite Mica (clear, brownish)
How to Analyze Igneous Rocks STEP 1 and 2-Study the Color and Mineral
CompositionDark-Mafic Minerals (no feldspar)
Biotite Mica (black)Amphibole (dark gray)Pyroxene (dark green)Olivine (green)
How to Analyze Igneous Rocks STEP 3-Study the Texture
IntrusivePegmatitic (crystals >1 cm)Phaneritic (crystals 1-10 mm)Porphyritic (large and small crystals indicate that it cooled at
TWO different rates)
How to Analyze Igneous Rocks STEP 3-Study the Texture
ExtrusivePorphyritic (large and small crystals indicate that it cooled at
TWO different rates)Aphanitic (crystals < 1mm)Glassy (like glass, crystals too small to see)Vesicular (small or large bubbles, like pie meringue or froth)Pyroclastic- particles emitted from volcano
Now, put it all together!
Now, put it all together!
What is this Igneous Rock? Light or Dark? Coarse or Fine Grained?
What is it?
What is this Igneous Rock? Light or Dark? Coarse or Fine Grained?
What is this Igneous Rock? Granite Yes, both are granite-one
gray and one red!
What is this Igneous Rock? Light or Dark? Coarse or Fine Grained?
What is this Igneous Rock? Light or Dark? Coarse or Fine Grained?
What is this Igneous Rock? Rhyolite
What is this Igneous Rock? Light or Dark? Coarse or Fine Grained?
Be careful with this one, it is really very fine grained with some larger white minerals.
What is this Igneous Rock? Rhyolite Porphyry
What is this Igneous Rock? Light or Dark? Coarse or Fine Grained? What is the unique
texture?
What is this Igneous Rock? Pumice
What is this Igneous Rock? Light or Dark? Coarse or Fine-grained? What is the unique
texture?
What is this Igneous Rock? Light or Dark? Coarse or Fine grained?
What is this Igneous Rock? Basalt
Some Igneous Rocks to Know Granite Gabbro Rhyolite Basalt Scoria Pumice Rhyolite Porphyry
Wrap-ups1. What are rocks?2. What is the Rock Cycle?3. What is the difference between magma and lava?4. What are the three types of rocks?5. What is a batholith? Sill? Laccolith?
Wrap-upsName the rock described:
6. Light colored, coarse grained.7. Dark colored, coarse grained.8. Light colored, very fine grained9. Spongy looking and light in color.10. Dark and glassy looking.
