Rocks Igneous, Metamorphic, Sedimentary What is a Rock? A rock is a mixture of minerals,...
-
Upload
merryl-stone -
Category
Documents
-
view
219 -
download
0
Transcript of Rocks Igneous, Metamorphic, Sedimentary What is a Rock? A rock is a mixture of minerals,...
What is a Rock?
A rock is a mixture of minerals , mineraloids, glass and organic matter.
Common minerals found in rocks include: feldspar, hornblende, and mica.
Granite is a mixture of these minerals.
Rock Cycle
There are three types of rock: Igneous – formed by melting and cooling magma
and lava. Sedimentary – formed by weathering and erosion Metamorphic – formed by heat and pressure over
time. Rocks change over time.
Igneous Rocks
Molten or liquid material from a volcano or from deep inside the Earth, cools to form igneous rocks.
Magma – High temperatures and high pressure deep in the Earth cause rocks to melt and form hot magma.
Igneous Rocks
At 60 to 200 km below the Earth’s surface the temperatures reach 1400oC. (2550oF)
Magma rises because it is less dense than the surrounding solid rock.
Igneous Rock: Intrusive Rocks
These are igneous rocks that form below the Earth’s surface.
They have large mineral grains. Examples : Gabbro
Diorite
Igneous Rocks:Extrusive
These rocks are formed quickly when lava cools on or near the Earth’s surface.
Air and Moisture causes lava to cool quickly. The quick cooling does not allow large crystals to
form. Extrusive rocks have a fine-grained structure.
Igneous Rocks: Extrusive Scoria - formed from gassy lava, it has air-pockets that give it a spongy appearance.
Pumice: Lava “foam”, some samples float in water.
Igneous Rocks: Vocabulary Mafic – composed of ferromagnesian minerals-
olivine, pyroxene, and amphibole. These are oceanic. The water cooled them quickly.
Felsic – composed of mostly quartz and feldspar.These are continental, cooling on dry land.
Igneous Rock
Aphamitic – texture , made of crystals too small to be seen without a microscope.
Porphyritic – rocks with two cooling rates,
They have a mix of large and small crystals. Porphyritic = look like chocolate chips! cookies
Igneous Rocks Texture – Cooling Rate – Crystal Size – Description - Type
Vesicular -fast- none - air bubbles – extrusive Glassy – fast – none - very smooth – extrusive Aphanitic –quick–microscopic –fine grained - extrusive
Granitic – slow – visible – coarse grained - intrusive Porphoritic – slow/then quick – small&large – Chocolate
chip - Intrusive
Mineral Composition of Igneous Rocks
Name – Minerals – Color – Density- Crustal Formation
Felsic – K-Feldspar, muscovite, quartz – Light – Low density – Continental
Intermediate- Hornblende, biotite, Na-plagioclase – Medium – Medium density – Continental/Ocean
Mafic – Olivine, Augite, Ca-plagioclase – Dark – High density - Oceanic