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8/13/2019 lecture_08_2011_v0
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Interlude B:
Rock Groups
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Rocks are:
Coherent
Naturally occuring
Aggregates ofminerals or masses of
glass
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How are rocks held together?
Grains are heldtogether by cement
A. Clastic rocks
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How are rocks held together?
Crystals interlock
B. Crystalline rocks
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How are rocks held together?
Form as a continuousmass
Grains welded together
while hot
C. Glassy rocks
http://www.es.ucl.ac.uk/schools/Glossary/obsidian.jpg
obsidian
Welded volcanic ash
http://darkwing.uoregon.edu/~dogsci/2/kays
/313/igfig45.jpg
http://www.nio.org/userfiles/image/projects/photomicrograph_1a.jpg
Volcanic
glass
Olivine
crystal
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Rocks are classified based on
how they form.
Solidification of molten rock
A. Igneous rocks
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Rocks are classified based on
how they form.
Pre-existing rocks break up, then grains
are cemented together
B. Sedimentary rocks
Darragh McDonagh (Geological Survey of Ireland)
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Rocks are classified based on
how they form.
Precipitation of mineral crystals
(evaporites)
B. Sedimentary rocks
http://www.travelvivi.com/wp-content/uploads/2009/12/Dead-Sea.jpg
Creative Commons / Wilson44691
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Rocks are classified based on
how they form.
Pressure and temperature cause solid
state changes
C. Metamorphic rocks
http://geophysics.ou.edu/geol1114/notes/met_rx/mica_garnet_schist.jpghttp://w
ww.nvcc.edu/home/cbentley
/gol_135/sideling_hill/images
/shale.JPG
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For each rock type, other characteristics are NB
Grain size and shape
Composition (elements, minerals)
Igneous rocks Sedimentary rocks
Metamorphic rocks
NB = important (nota bene)
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For each rock type, other characteristics are NB
Texture
E.g., smallest to largest
E.g., alignment
Igneous rocks Sedimentary rocks
Metamorphic rocks
NB = important (nota bene)
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For each rock type, other characteristics are NB
Layering
E.g., Bedding
Igneous rocks Sedimentary rocks
NB = important (nota bene)
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For each rock type, other characteristics are NB
Layering
Foliation
Metamorphic rocks
NB = important (nota bene)
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Thin sections (photomicrographs) are a way to
look at microscopic details
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Thin sections (photomicrographs) are a way to
look at microscopic details
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Interlude C:
Rock Cycle
8-22
8 23
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8-23 Rock cycle: materials move from one rock
type to another
8 24 H d thi k?
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8-24 How does this work?
Igneous rocks form
Sedimentary(from igneous rocks igneous
igneous
Sedimentary, metamorphic,
igneous rocks are melted
Plates collide
Ocean crust
recycled into
mantle
8 25 H d thi k?
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8-25 How does this work?
igneous
sedimentary
metamorphic
(sedimentary and igneous rocks
heated and compressed)
(Sedimentary, metamorphic,
igneous rocks have been eroded)
Plates collide and lock
8 26 H d thi k?
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8-26 How does this work?
sedimentary
igneous
(Sedimentary, metamorphic,
igneous rocks have been eroded)
metamorphic
Plates stop moving, erosion happens
8 27 H d thi k?
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8-27 How does this work?
Igneous rocks forming
(Sedimentary, metamorphic,
igneous rocks are being melted)
A rift forms, plates move apart