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Geol Test #1
Jules' test
100
Geology
Undergraduate 2
02/08/2011

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Cards

Term
Geology
Definition
The science that pursues an understanding of planet Earth
Term
Physical geology
Definition
Examines the materials composing Earth and seeks to understand the many processes that operate beneath and upon its surface
Term
Relative dating
Definition
means that dates are placed in their proper sequence or order
Term
Radiometric
Definition
gives precise dates
Term
Density
Definition
mass/volume
Usually in grams per cubic centimeter gm/cc
Term
Density Stratification
Definition
Solid earth, oceans and atmosphere have layers based upon density differences, they are density stratified
Term
15 BYA
Definition
Big bang: expansion of the universe-first stars and galaxies formed.
Term
5 BYA
Definition
Cloud of gas and space dust (nebula) began to contract forming Proto-planets
Term
4 BYA
Definition
The earth's oceans were essentially in place. Oldest rocks from Canada are of this age.
Term
1.5 BYA
Definition
Oxygen production greatly accelerated from green plants.
Term
<1 BYA
Definition
First multi-cellular organisms appear
Term
540 MYA
Definition
Phanerozoic Time begins
Term
Nebular hypothesis
Definition
• Assumes a flat, disk shape with the protosun (pre-Sun) at the center
• Inner planets form from metallic/rocky substances
• Larger outer planets began forming from fragments of ice (H2O, CO2, and others)
Term
Proto-earth formed
Definition
• Initially homogenous
• Larger in size than today’s Earth
• No continents or oceans, or life
• Denser materials sank to the center
• Early crust began to form
Term
Volcanic outgassing
Definition
Produced large volumes of water and formed earths primitive atmosphere of carbon dioxide, nitrogen, methane, and ammonia.
Term
Uniformitarianism
Definition
• Late 1700’s “the age of modern geology “ James Hutton
• The present is the key to the past
• The way to understand the Earth's history is by comparing to current processes and events
• Most geologic changes occur slowly over long periods of time.
Term
Earth's spheres
Definition
• Atmosphere
• Hydrosphere
• Biosphere
• Solid Earth
Term
Earth’s surface features
Definition
Continents:
• Stable interior
• Mountain belts

Ocean basins
• Continental margins
• Deep-ocean basins
Term
Igneous rocks
Definition
Solidification of magma (at depth) and lava (on surface)
Ex: granite and basalt
Term
Sedimentary rocks
Definition
Derived from weathering of pre-existing rocks. Often contain fossils and indicative internal structures.
Ex: sandstone and limestone
Term
Metamorphic rocks
Definition
Formed by “changing” pre-existing igneous, sedimentary or other metamorphic rocks
• Driving forces are increased heat and pressure.
Ex: gneiss and marble
Term
How do we know the structure of the earth?
Definition
• Seismic (earthquake) waves
• Gravity measurements
• Magnetic measurements
Term
Seismic waves
Definition
• Earthquake waves that traveling through the earth
• two types of waves: surface waves and body waves
• surface waves travel on the surface
• body waves travel through the earth
• there are two main types of body waves: P and S waves
Term
P (primary) waves
Definition
Primary
Compressional (Parallel)
Faster
Solids, liquids, and gas
Term
S (shear) waves
Definition
Secondary
Shear(Perpendicular)
Slower
Solids only
Term
Earths Shadow Zones
Definition
P and S waves both go through solids. S waves do not go through non-solids, so only P waves are received on the opposite side of the earth.
Term
What can P and S wave data tell us?
Definition
1. Parts of the earth are not solid.
2. The depth and location of an earthquake (EQ)
3. The relative strength of an EQ
4. The average density of earth.
5. The density of each layer in the earth.
Term
Gravity measurements
Definition
tell us that there must be denser material deeper in the earth through the gravity formula
Term
Magnetic measurements
Definition
• Formed from convection in the liquid outer core
• Tells us about the composition and physical properties in the interior of the Earth.
• There must be significant amounts of iron for earth to have such a strong magnetic field.
Term
Earth's layers defined by composition
Definition
Crust
Mantle
Core
Term
Crust
Definition
• Composed of light silicates rich in aluminum.
• Comparatively thin outer skin that ranges from 3 km at the oceanic ridges to 70 km in some mountain belts.
• Separated into thin oceanic (3.0 gm/cc) and thicker continental crust (2.7 gm/cc)
Term
Mantle
Definition
• Composed of heavier silicates rich in iron and magnesium
• Large portions can flow slowly and are near melting.
Term
Core
Definition
• An iron-nickel rich sphere
• Outer core is liquid, convection here sets up earth’s magnetic field
• Inner core is solid and very dense
Term
Layers defined by physical properties
Definition
Lithosphere
Asthenosphere
Methosphere (lower mantle)
Outer core
Inner core
Term
Earth's major boundaries
Definition
Mohorovic discontinuity
Core mantle boundary
Lehman discontinuity
Term
Plate Tectonics
1600 - 1700's
Definition
It was noticed that charts of land masses in the new world "fit" together like a puzzle.

Geologic and fossil trends indicated that some land masses which are now separated may have been together at some point in time.

Nobody could provide a mechanism for the continents to move.
Term
Alfred Wegener
Definition
1912

German with PhD is astronomy and interest in meteorology.

Proposed the concept of continental drift in a lecture.
Term
Pangea
Definition
Name given by Alfred Wegener for original land mass
Term
What did Alfred Wegener propose about the original landmass?
Definition
continents started moving about 200 million years ago (MYA) and they are still moving. This is amazing because it is pretty accurate.
Term
What were Alfred Wegeners conclusions about continental drifting based on?
Definition
Fossil evidence of Mesosaurus (reptile), Glossopteris (plant) and the present distribution of plants and animals especially marsupial mammals.
Term
What did geophysicists Wadati and Benioff delineate in the 1940's?
Definition
They plotted deep earthquakes and delineated the "Ring of Fire".
Term
When was radiometric age dating developed
Definition
1940's.
Term
How old is the oldest continent?
Definition
More than 3 BYO
Term
How old is the oldest sea floor?
Definition
About 200 MYA
Term
Who claimed that continents plowed through the oceanic crust?
Definition
Alfred Wegener.
Term
What did Harry Hess propose in the 1960's?
Definition
That the continents did not plow through the oceanic crust (Wegener) but were riding with the oceanic crust like a conveyor belt.
Term
What is the definition of Plate Tectonics?
Definition
A theory that states that the earth's solid outer shell (lithosphere) broken into "plates" can move relative to each other while sitting over a plastic, non-solid layer called the astenosphere.
Term
What is thought to be the driving force of plate tectonics?
Definition
Convection in the asthenosphere
Term
Which boundary is the most important for plate tectonics to occur?
Definition
The lithosphere/asthenosphere boundary
Term
What happens in plate tectonics where the solid lithosphere plates meet?
Definition
We see the most volcanic and seismic activity.
Term
What is the evidence for plate tectonics?
Definition
A) Continental drift
B) Plate boundaries
C) Hotspots
Term
What is the evidence for continental drift?
Definition
1. the shape of the continents
2. fossil evidence
3. geologic features (old mountain ranges spanning contenental boundaries)
4. Paleomagnetism
5. The sedimentary rock record
Term
What are the three types of plate boundaries?
Definition
1) Divergent (pulled apart, tensional force)
2) Convergent (pushed together, compressional force)
3) Transform (sliding past or rotational)
Term
What are the two signs of divergent plate boundaries?
Definition
1. Seafloor spreading
2. Continental rifting
Term
What is the process of seafloor spreading?
Definition
Tensional forces pull oceanic crust apart.
Mid oceanic ridge forms
Lava rises, new seafloor surface
Older is more dense, gets pulled away from ridge
Term
A rise...
Definition
Spreads faster and is less steep
Term
A ridge...
Definition
is steeper and spread slower
Term
East pacific _____?
Definition
rise
Term
Mid-atlantic ____?
Definition
Ridge
Term
How does continental rifting occur?
Definition
Continental crust pulls apart
Large amount of sediment produced
Forms lakes and rivers, finally an ocean
Term
What is an old continental rift?
Definition
Africa pulling apart from SA
Term
What are two present continental rifts?
Definition
1. Red Sea
2. East Africa Rift System
3. Djiboti
Term
What are the features of convergent plate boundaries?
Definition
• Plates move together and collide so you have compressional forces
• Active margins: mountain building, earthquakes, and andesite (explosive) volcanoes.
• Most dangerous type
• Earthquakes up to 9.5 in subduction zones
• Andesite volcanoes: very explosive
• Tsunami potential where you have subduction.
Term
What are the three types of convergent plate boundaries?
Definition
1. Subduction of OC beneath CC
2. Subduction of OC beneath OC
3. Continental collisions, CC colliding with CC
Term
What happens in the subduction of OC beneath CC?
Definition
• Denser, thinner OC is pushed or subducted beneath less dense and more buoyant CC.
• Called a continental volcanic arc.
• Deep and shallow (tsunami potential) focus earthquakes, the largest ever 9.5 magnitude in Peru/Chile Trench in 1960
• Andesite (explosive) volcanoes, like the Cascade Range: Mt. St. Helens etc.
• Deep trenches form around continents (more on trenches later). Especially when far away from spreading centers.
• Reduces amount of (destroys) OC.
• Rates up to 15 cm/yr in the active margins of the Pacific Basin
Term
What happens in the subduction of OC beneath OC?
Definition
• Many similar features as above.
• Denser, older, cooler OC is pushed or subducted beneath less dense, warmer, younger OC.
• Forms island volcanic arcs
• Deep and shallow (tsunami potential) focus earthquakes
• Volcanoes not as explosive as above with OC/CC, as there is no mixing of CC rocks (called granites). Mostly basaltic.
• Reduces amount of (destroys) OC.
Term
What happens in a Continental Collision? CC colliding with CC?
Definition
• Neither of the CC are subducted,
• Both are very buoyant and want to "float" or ride high.
• This is where you form the very large mountain chains.
• Mountain building
• Earthquakes
Term
What are the three types of transform boundaries?
Definition
1. Continental transform faults
2. Oceanic transform faults
3. Hotspots and mantle plumes
Term
What are the features of Continental Transform Faults?
Definition
• In CC we have large destructive faults like the San Andreas.
• Magnitudes up to 8.5 have been measured.
• Rates on the San Andreas average 2-5 cm/yr or LA will be adjacent to SF in about 20 million years.
• Where these faults bend or change direction you can get local compression (and uplift) like Mt Soledad or tension (and down-warping)
Term
What are the features for Oceanic Transform Faults?
Definition
• In OC, perpendicular to the spreading centers we have smaller transform faults.
• They have smaller earthquakes associated with them, when compared with their continental cousins.
• These faults occur where there is a bend or change in the rate of spreading along the MOR.
Term
What are the features of hotspots and mantle plumes?
Definition
• These are hotspots beneath the lithosphere caused by rising plumes of mantle material
• Can form volcanoes on surface:
-Mostly mafic (basaltic) as these lavas are very fluid.
-Less common are felsic (rhyolitic) magmas as they are thicker and less prone to flow.
Term
Where are the Hawaii volcanoes formed?

What type of volcanoes are they?

How long has the hotspot existed?
Definition
Underneath oceanic crust,

Forms basalt (non-explosive) volcanoes,

This hotspot has existed for about 60 MY's.
Term
Where is the Yellowstone hotspot?

What types of volcanoes?

How many times has it erupted in the last 2 million years?
Definition
Underneath continental crust

Forms rhyolitic and other types of volcanoes

Has had large rhyolitic eruptions 3 times in the last 2 million years
Term
What drives plate motions?
Definition
Convective flow in the mantle
• Slab-pull
• Ridge-push
• Convective friction
Term
What is the importance of plate tectonics?
Definition
• The theory provides explanations for many of earth’s major processes
• The geologic distribution of earthquakes, volcanoes, and mountains
• The distribution of ancient organisms and mineral deposits
• Plate tectonics are responsible large volumes of oil and gas deposits we enjoy today.
Term
Which two major interior parts (not lava or magma) of the earth are non-solid?
Definition
a) Asthenosphere
b) Outer core
Term
What is the Moho?
Definition
Moho stand for the Mohorovicic discontinuity. It is one of the Earth’s major boundaries which separates the crust and the mantle. First discovered in the early 1900’s by a Croatian named Andriaja Mohorovicic who interpreted the gathering speed of P waves as a change of composition beneath the Earth’s surface.
Term
What is the average thickness, density and rock type of continental crust?
Definition
a) About 25 miles thick
b) About 2.7 g/cm3
c) Many rock types with a granitic rock called granodiorite showing up the most.
Term
What is the average thickness, density and rock type of oceanic crust?
Definition
a) About 5 miles thick
b) About 3.0 g/cm3
c) Basalt (igneous rock)
Term
Describe or orign of andesite volcano.
Definition
An andesitic volcano is formed when tectonic plates produce a large amount of friction by rubbing together, generating enough heat to produce molten rock known as magma. The magma is then pushed through the earth’s surface and gradually becomes solid, forming the volcano.
Term
Name the three types of plate boundaries and give one common (name place/area) example location for each.
Definition
a. Divergent – Iceland
b. Convergent – the Andes
c. Transform – Hawaii
Term
Lithosphere
Definition
• Consists of the crust and uppermost mantle
• Relatively cool, rigid shell
• Averages about 100 km in thickness, but may be 250 km or more thick beneath the older portions of the continents
Term
Asthenosphere
Definition
• Beneath the lithosphere, in the upper mantle to a depth of about 600 km
• Behaves plastically and can mechanically detach and move independently of the lithosphere.
Term
Mesosphere or lower mantle
Definition
• Rigid layer between the depths of 600 km and 2900 km
• Rocks are very hot and capable of very gradual flow
Term
Outer core
Definition
• Liquid layer
• Composed mostly of an iron-nickel alloy
• Convective flow within generates Earth’s magnetic field
Term
Inner core
Definition
• Behaves like a solid
• Very dense around 16 gm/cc
Term
The Moho
Definition
• Discovered in 1909 by Andriaja Mohorovicic
• Separates crustal materials from underlying mantle
• Identified by a change in the velocity of P waves
Term
The core-mantle boundary
Definition
• Discovered in 1914 by Beno Gutenberg
• Based on the P-wave shadow zone
• No P waves from 105 to 140 degrees
• S waves do not travel through the outer core provides of liquid outer core below the mantle
Term
Lehmann Discontinuity
Definition
• Predicted by Inge Lehmann in 1936
• Boundary between outer and inner core
• Increase in velocity from outer to inner core
• Reflection off solid inner core
Term
Harry Hess
Definition
Undergrad Yale, graduate Princeton
A professor of geology at Princeton University, was very influential in setting the stage for the emerging plate-tectonics theory in the early 1960s
Term
Who put the Theory of Plate Tectonics together along with Harry Hess?
Definition
Vine and Matthews (Paleomagnetism), and Tuzo Wilson (plate boundaries)
Term
What is an example of OC subducting beneath CC?
Definition
Andes and Cascades
Term
What is an example of OC subducting beneath OC?
Definition
Aleutian Islands SW of Alaska
Japan
Tonga Islands
Phillipines
Term
What is an example of CC colliding with CC?
Definition
Himalayas (India) 45 MYA
Appalachians (East Coast NA) 350-400 MYA
Term
What is the general range of rates that seafloor spreading occurs?
Definition
5-15 cm per year.
Term
A fracture is just a _____ if it moves it becomes a _____
Definition
Crack, fault
Term
Continental transform faults
Definition
1. Cool
2. Hard to move
3. Large EQ
Term
Oceanic transform faults
Definition
Warm
Easy to move
Lost of small EQ
Term
"D" Layer
Definition
Between rocky mantle and outer core.
Term
Distance from an EQ
Definition
P waves arrive at the seismometer first, followed by the S-wave. Once the S-wave arrives.

The difference in the arrival times of the waves is distance from earthquake
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