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Historical Geology
Historical Geology Wagner Texas State GEOL 1420
75
Geology
Undergraduate 1
02/02/2014

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Term
What are the steps of the scientific method
Definition
question>research>hypothesis>experiment>analyze>results.
Term
What is a hypothesis
Definition
a procisional explanation for observations that is subject to continual testing and midification if necessary; if well supported by evidence, hypotheses may become theories
Term
What is a theory
Definition
an explanation for some ntural phenoenon with a large body of supporting evidence; theories must be testable by experiments and or observations, as is the case with plate tectonic theory
Term
What are the three main themes of historical geology
Definition
Plate tectonics, time, evoluionary theory
Term
What about the gerbil?
Definition
gerbil is what happens when things die
Term
What is the definition of a mineral
Definition
A naturally ocurring, inorganic, crystalline solid having characteristic physical properties and a narrowl defined chemical composition.
Term
What is the classification system for minerals?
Definition
1. Naturally occuring 2. inorganic solid 3. crystalline structure 4. narrowly defined chemical comp. 5. with particular physical properties.
Term
What are the non-silicate types of minerals?
Definition
Oxides, Carbonates, Sulfides, Sulfates.
Term
What are the silicate types of minerals?
Definition
Halides, Phosphates, Hudroxides, Native elements.
Term
What are some of the most important mineral groups for historical geology?
Definition
Silica minerals (quartz), Feldspars, Clays, Calcite, Gypsum, Halite, Iron-oxide minerals (ferromagnesian minerals)
Term
What are characteristics of Quartz?
Definition
(almost) pure silica, macrocrystalline structure = quartz (large crystals), Microcrystalline structure = Chalcedony (micro), Conchoidal fracture, very hard (7ish) Very stable, Nearly isotropic.
Term
What is the most common MINERAL in the earth's CRUST?
Definition
Feldspars
Term
Feldspars characteristics
Definition
Similar to quartz but with a bit of metal, most common mineral in crust, two clevage planes, unstable at surface (weather to clays)
Term
What are the most abundant minerals at the SURFACE
Definition
Clay Minerals
Term
Characteristics of clay minerals?
Definition
Sheet silicates, Most abundant at surface, Stacks of sheets, Floculate (form clumps) microscopic, soft, form mud.
Term
What's with calcite?
Definition
Calcium carbonate, effervesses, soft, three clevage planes, secreated by organisms to make shells, polymorph: aragonite. Similar to dolomite.
Term
Gypsum, what's it all about?
Definition
Calcium sulfate, highly soluble, usually formed by concentration of water, very very soft, three clevage planes, used in drywall, sand at white sands beach.
Term
Halite
Definition
salt
Term
Iron oxides
Definition
commonly the cement in sedimentary rocks, often distinctly colored.
Term
ferromagnesian minerals
Definition
silicates, rich in iron and magnesium, unstable at earths surface, bulk of earths mantle, dark colored.
Term
What kind of information can you get from minerals?
Definition
Molecular chemistry = enviroment and conditions of formation.

Nuclear chemistry = radiometric dating

Thermodynamic stability = related to their chemistry and crustalline structure. temperature and pressure.
Term
What is a rock?
Definition
A solid aggregate of minerals
Term
How are rocks classified?
Definition
by how they form
Term
What are the three basic types of rocks?
Definition
Igneous, metamorphic, sedimentary
Term
How are rocks classified within each group?
Definition
Texture: side and arrangement of grains, compisition: minerology
Term
What are igneous rocks?
Definition
Rocks formed by solidification of magma
Term
What are intrusive igneous rocks?
Definition
formed below earths surface (plutonic)
Term
what are extrusive rocks?
Definition
formed above earths crust (volcanic)
Term
What do igneous rocks tell us?
Definition
Chemistry of magma source, temperature and pressure history of magma, large scale tectonic events.
Term
What is ultramafic compisition
Definition
composition of the mantle, high ferromagnesian content, very dense, dark, low magma viscocity, never extruded. (peridotite)
Term
What is mafic composition?
Definition
composition of oceanic crust, high ferromagnesian content, dense, dark, low magma viscosity, associated with crustal divergence. (Gabbro, Basalt)
Term
What is intermediate?
Definition
Often found as mixed mafic/felsic rock, reasonable ferromagnesian content, not very dense, medium grey, moderate to high magma viscosity, associated with crustal convergence. Diorite, Andesite. (salt and peppery?)
Term
What is Felsic rock?
Definition
Igneous rock, Often found as mixed mafic/felsic rock, Low ferromagnesian content (mostly feldspar and quartz) Low density, Light colored, High magma viscosity, bulk composition of continental crust. (granite, rhyolite, Erock)
Term
What type of rock is granite?
Definition
Felsic INTRUSIVE rock. Formed underground! Enchanted rock!
Term
What type of rock is basalt?
Definition
Mafic EXTRUSIVE rock. Formed underwater, above crust!
Term
What type of information can you get from igneous rocks?
Definition
mantle viscosity.....
Term
Definition of Metamorphic rock
Definition
Rock formed through the alteration of other rocks by some combination of: Heat, Pressure, Hot aqueous fluids
Term
What can metamorphic rock tell us?
Definition
Local temperature/pressure, general geochemical history, information about the protolith.
Term
What causes metamorphism
Definition
Changes in pressure, temperature and chemistry change mineral stability.
Term
What are some ways minerals change
Definition
Dissolution, recrystallization, growth. No change in bulk, loss of water.
Term
What is foliation?
Definition
foliation is repetitive layering formed perpindicular to directional pressure and stress causes recrystallization or formation of new minerals in response to pressure.
Term
Non foliated?
Definition
Usually made from a single predominant mineral, Usually very specific to protolith, tend to give less information.
Term
What is contact metamorphism
Definition
Local scale, contact aureole, significant increase in heat, may also involve hot fluids. May be indirect evidence for magmatic activity.
Term
What is burial metamorphism
Definition
basin-scale, generally along local geothermal gradient, Leads to info about tectonics and sedimentation.
Term
what is regional metamorphism
Definition
continental scale, inscreased directional pressure (predominant), often involves folding faulting. Closely tied to tectonics.
Term
what is shock Metamorphism
Definition
local scale, extreme pressure, relavant to hisory of life. Meteors!
Term
what is metamorphic grade
Definition
degree of alteration of protolith
Term
What is facies?
Definition
Distinct combinations of index minerals
Term
What is diagenesis
Definition
Changes in a sediment or sedimentary rock below 200C, compaction, cementation, minor minerological change, removes information.
Term
What is clastic sedimentary rock?
Definition
Made of pieces of other rocks, comes in grain sizes, grain minerology, info comes from sediment.
Term
What are some types of sandstones?
Definition
Quartz arenite, Arkose, Litharenite
Term
What are chemical sedimentary rocks?
Definition
Made of chemicals dissoled from other rocks, and reprecipated. Usually oen predominant mineral, information comes from sediment and diagenesis
Term
What are some carbonate examples?
Definition
Limestone (calcite or aragonite), Dolostone (diagenetic alteration of limestone)m Organic or evaporitic (fossils, aragonite, warm shallow seas)
Term
What are some examples of evaporites?
Definition
Limestone, gypsum, anhudrite, rock salt.
Term
What are some other chemical sedimentary rocks?
Definition
chert (silica), Coal, Glauconite
Term
What are the basics of hyposemetric curve and stream gradient?
Definition
The gradient shallows closer to deposition area, it is steep near soucce, grain size decreases closer to shore, further from source, glacial deposits are poorly sorted, wind deposits are very well sorted.
Term
Grain shape keys?
Definition
roundness is further from source, sharp is closer to source, except for feldspars and their clevage.
Term
what info can we get from sedimentary structures?
Definition
depositional enviroment, climate, weather, currents, post burial history, biological activity.
Term
what is a geopetal structure?
Definition
Indicates which way was up
Term
what does paleohorizontal mean?
Definition
which way was up?
Term
what is paleocurrent?
Definition
unidirectional, bidirectional current indicators
Term
What is an easy depositional environment?
Definition
breccia, always near source, cave ins, mountains etc... Shale, Coal, black shale, limestone,
Term
What is a not so easy depositional environment?
Definition
Arokse
Term
What are sedimentary facies?
Definition
associatons of sedimentary roccks and structures indicative of a particular depositional environment, also holographic
Term
What is eustasy
Definition
change in absolute sea level. A rise is refferred to transgression, a fall is regression
Term
What is isostacy?
Definition
A change in land level, a tectonic uplift is regression and a subsidence is transgration.
Term
Eustacy + isostacy
Definition
relative sea level change
Term
Sediment supply changes
Definition
Increased sedimentation is regression, increased coastal erosion and subsidence is transgression
Term
What does stratigraphy include?
Definition
mapping, measuring stratigraphic columns, documenting facies, interpreting depositional history
Term
What is stratigraphy?
Definition
The description and interpretation of sequences of layered rocks
Term
What is lithostratigraphy?
Definition
study of types of rocks
Term
what is biostratigraphy
Definition
study of distriution of fossils in rocks
Term
what is chronostratigraphy
Definition
study of relationships of rocks and time
Term
what is magnetostratigraphy
Definition
study of magnetic history of rocks
Term
what is a stratigraphic column?
Definition
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