geology macc bill palmer lecture 4 rocks. what are rocks? rocks are solid materials that comprise...

GEOLOGYMACC

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?

The rock cycle explains how all rocks can be formed, deformed transformed, destroyed, and reformed as a result of natural processes.

Rock Cycle

Materials 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 Cycle

There 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 STRUCTURES

1. 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)

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)

STEP 3-Study the Texture Intrusive

Pegmatitic (crystals >1 cm)Phaneritic (crystals 1-10 mm)Porphyritic (large and small crystals indicate that it cooled at

TWO different rates)

STEP 3-Study the TextureExtrusive

Porphyritic (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!

What is this Igneous Rock? Light or Dark? Coarse or Fine Grained?

What is it?

http://images.google.com/imgres?imgurl=http://www.uwm.edu/Course/422-100/Mineral_Rocks/granite2.jpg&imgrefurl=http://www.uwm.edu/Course/422-100/Mineral_Rocks/granite.data.html&h=553&w=737&sz=46&hl=en&start=19&tbnid=Wlt-ZcL5_tsbHM:&tbnh=106&tbnw=141&prev=/images%3Fq%3Dgranite%2Bspecimen%26gbv%3D2%26svnum%3D10%26hl%3Den%26ie%3DUTF-8%26sa%3DG

What is this Igneous Rock? Granite

http://images.google.com/imgres?imgurl=http://www.uwm.edu/Course/422-100/Mineral_Rocks/granite2.jpg&imgrefurl=http://www.uwm.edu/Course/422-100/Mineral_Rocks/granite.data.html&h=553&w=737&sz=46&hl=en&start=19&tbnid=Wlt-ZcL5_tsbHM:&tbnh=106&tbnw=141&prev=/images%3Fq%3Dgranite%2Bspecimen%26gbv%3D2%26svnum%3D10%26hl%3Den%26ie%3DUTF-8%26sa%3DG

http://images.google.com/imgres?imgurl=http://www.randall.k12.wi.us/rocks/images/granite.jpg&imgrefurl=http://www.randall.k12.wi.us/rocks/granite.htm&h=516&w=591&sz=81&hl=en&start=1&tbnid=5_B7Ac52wZiQHM:&tbnh=118&tbnw=135&prev=/images%3Fq%3Dgranite%2Bspecimen%2Bred%26gbv%3D2%26svnum%3D10%26hl%3Den%26ie%3DUTF-8%26sa%3DG

What is this Igneous Rock? Granite Yes, both are granite-one

gray and one red!

http://images.google.com/imgres?imgurl=http://www.randall.k12.wi.us/rocks/images/granite.jpg&imgrefurl=http://www.randall.k12.wi.us/rocks/granite.htm&h=516&w=591&sz=81&hl=en&start=1&tbnid=5_B7Ac52wZiQHM:&tbnh=118&tbnw=135&prev=/images%3Fq%3Dgranite%2Bspecimen%2Bred%26gbv%3D2%26svnum%3D10%26hl%3Den%26ie%3DUTF-8%26sa%3DG

http://images.google.com/imgres?imgurl=http://www.uwm.edu/Course/422-100/Mineral_Rocks/gabbro1.jpg&imgrefurl=http://www.uwm.edu/Course/422-100/Mineral_Rocks/gabbro.data.html&h=553&w=737&sz=54&hl=en&start=5&tbnid=-KufbDOfe_MsqM:&tbnh=106&tbnw=141&prev=/images%3Fq%3Dgabbro%2Bspecimen%2B%26gbv%3D2%26svnum%3D10%26hl%3Den%26ie%3DUTF-8%26sa%3DG

What is this Igneous Rock? Gabbro