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139 Cards in this Set
- Front
- Back
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What is one of the most convincing arguments for the super continent cycle hypothesis?
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The surprising regularity of mountain building caused by compression during continental collisions.
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What is proposed as the cause of the break up of the super continents?
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continental drift or super continents cycle hypothesis
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According to the super continents cycle hypothesis, how long is the cycle during which supercontinents form, break up, and reform?
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about 500 million years
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when did pangea begin to fragment?
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about 200 million years ago.
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Explain why the existence of guyots indicates that the sea floor is geologically young and that oceanic crust moves away from spreading ridges over time
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? |
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what is the max age for oceanic crust
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180 millon years
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what evidence for active seafloors did the discovery of guyots provide
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? |
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how do certain rock types record the locations of past magnetic poles
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Iron–bearing minerals align themselves in thedirection of the current magnetic field when the rock cools below theCurie point.
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why was the Glossopteris flora on Gondwana contients considered evidence for continental drift?
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because they are found in Pennsylvanian and Permian coal deposits on all 5 Gondwanaland continents
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what are the lines of evidence which were cited for continental drift
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fossil evidence, glacial evidence, seafloor spreading, plate tectonics.
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what presently accepted piece of evidence for continental drift/plate tectonics was first observed as early as 1620?
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Francis Bacon observed that Africa and South America had similar shorlines
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what are 4 of the many things which plate tectonic theory explains or whose explanations it has influenced?
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the distributions of earthquakes and volcanoes,the locations of ore deposits and mountain systems, climatic patternsand ocean circulation, the geographic distribution, evolution andextinction of life forms
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a transform boundary may connect
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a spreading ridge and a subduction zone, two spreading ridges, or 2 subduction zones.
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the forces operating at continent–continent convergent plate boundaries are
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compressional
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at divergent plate boundaries, the forces operating are
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tensional
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Studies of paleomagnetism showed that
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older rocks showed the north pole in a different place as the younger rocks as well as the present rocks.
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which structural layer of Earth comprises the greatest volume of earth
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mantle
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Which structural layer of earth is thinnest and least voluminous?
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crust
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which structural layer of earth is liquid?
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outer core
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what is the major source of information used in developing this model of earth's interior?
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earthquakes
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velocities of P and S waves are determined by which two physical properties of the material through which they pass?
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elasticity
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why are the paths of seismic waves curved?
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because of the density and elasticity forces
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what are two important and very useful differences between p and s waves
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P are faster and trave through liquid and gases while S waves are slow and don't travel through gases and liquids
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what happens to P and S waves when they encounter the core–mantle boundary?
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S waves stop and P waves continue
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Why the outer core can be liquid at temperatures of 3500 – 5000 degrees C while the inner core is solid
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Pressure and composition. The outer core experiences more pressure than the inner core.
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what significant boundary occurs at a depth of approximately 30 km beneath earth's surface?
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asthenosphere
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instead of x rays used in CAT scans, what energy is used in seismic tomography?
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seismic waves
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for what purpose is seismic tomography used
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In order to map the inside of the earth, seismographs all over the world to sweep Earth's interior in many different directions and construct a three–dimensional image of what's inside.
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what are the major elements comprising the earths core
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nickel and iron
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what does the abrupt change in behavior of P and S waves at the core boundary indicate about the core?
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part of it is liquid
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where is the continental crust the thickest?
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Mountain ranges
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Where is the continental crust the thinnest?
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spreading centers. rift zones, divergent zones
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where is the oceanic crust thinnest?
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spreading zones
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continental crust has a mineral composition like that of and is known as granitic crust
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True
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which igneous rock is considered the most likely candidate for representing the composition of the mantle?
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peridotite
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what is the geothermal gradient?
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temperature increase with depth. 25 degrees C per km.
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why do we know that the geothermal gradient near the surface cannot continue very deeply into earth
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because near the surface, temperatures can be affected by external factors such as the sun.
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what is an estimate of the temperature range at the base of the crust
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200 – 400 degrees C
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what is an estimate of the temperature at the core–mantle boundary?
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about 4000 degrees C
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what is the primary source of the earths internal heat?
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radioactive decay of chemical elements
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what is meant by the term "gravity anomaly"?
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the difference between the observed acceleration of a planet's reaction to gravity and a value predicted from a model
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what causes a positive gravity anamoly?
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. A location with a positive anomaly exhibits more gravity than predicted
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what is isostatic rebound?
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the gradual rising of land elevations as it springs back after thousands of years of being crushed under the weight of continental glaciers
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Explain why, according to the principle of isostasy, continential crust should be thicker than oceanic crust?
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the oceanic crust is thinner due to the weight of the water pressing down on the crust.
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what is isostasy?
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state of gravitational equilibrium between Earth's crust and mantle such that the crust "floats" at an elevation that depends on its thickness and density.
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Given the phenomenon of isostatic rebound, what happens to the depth of a mountain range's roots as it is eroded?
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as a mountain range is eroded, the (reduced) range rebounds upwards (to a certain extent) to be eroded further. Some of the rock strata now visible at the ground surface may have spent much of their history at great depths below the surface buried under other strata.
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what is meant when earth's magnetic field is described as dipolar
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? |
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what is the Curie point?
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the temperature at which certain materials lose their permanent magneticproperties, to be replaced by induced magnetism
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What is the best explanation for how the earth's magnetic field is generated?
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is believed to be generated by electric currents in the conductive material of its core, created by convection currents due to heat escaping from the core.
Basically : outer core is made of iron = good conductor liquid = convection = motion that creates electric currents |
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What are magnetic anomalies?
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A magnetic anomaly is a deviation in the Earth's magnetic field from the overall average expected for the area. Magnetic anomalies are most often attributed to differences in the composition of the lithosphere
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lithosphere
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the solid rock crust surrounding the Earth's molten core
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what is paleomagnetism?
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study of the record of the Earth's magnetic field in rocks, sediment, or archeological materials
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What is a magnetic reversal?
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A change in the Earth's magnetic field resulting in the magnetic north being aligned with the geographic south, and the magnetic south being aligned with the geographic north.
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What is a cause of a positive magnetic anomaly?
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a body of magnetic ore, an intrusion of gabbro or, mafic rock masses
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Given two objects of the same mass, one at sea level, and the other atop Mt. Everest, which has a greater weight?
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the object at the lower altitude due to the distance from the center of the earth
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What plate tectonic setting is responsible for the large mountain systems of the world?
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convergence
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what is the definition of stress?
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Types of forces at work
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what is the difference between stress and strain?
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stress is the type of force at work and strain is the result of stress
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What are the three types of stress?
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compression, tension, sheer
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what happens if a rock is strained beyond its elastic limit?
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fracturing occurs
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What is the difference between brittle and ductile rocks?
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Brittle rocks fracture more and are closer to surface while ductile rocks don't fracture and are generally farther from the surface.
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what is the strike of an inclined rock layer?
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direction of intersection at horizontal and dipping plains
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what is the dip of an inclined layer of rock?
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angle that the bed dips
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a fold is a result of what kind of deformation?
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plastic
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what type of fold is an up–arched fold?
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anticline
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In an anticline, the beds in its axial region are (BLANK) than the beds of its limbs and all strata dip (BLANK) the axis
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older, away from
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what type of fold has axial beds which are younger than those of its limbs and limbs which dip toward its axis?
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syncline
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what can we say about a fold if both its limbs dip in same direction?
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symmetrical
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what is the difference between faults and joints?
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joints are fractures that show no lateral movement
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which type of fault is one in which the hanging wall has moved upward relative to the footwall?
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reverse fault
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what type of fault is created by tensional forces?
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normal fault
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which type of fault is one in which the hanging wall has moved downward relative to the footwall?
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normal fault
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what type of fault is caused by sheering forces?
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strike slip faults
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what kind of fault is the infamous San Andreas Fault in California?
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strike slip fault
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How is a fault classified when it has components of both dip–slip and strike–slip movement?
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oblique slip
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What are three ways in which mountains form?
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convergence, spreading zones, hot spots, Accretion.
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what type of forces produce block fault mountains such as those in the Basin and Range Province of teh southwestern United States?
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Tension
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What is an orogeny?
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Mountain building process
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What percentage of the Pacific Coast of N. America is thought to be composed of microplates?
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25%
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What is the age of the oldest known rocks that have been dated in North America?
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3.96 billon. Part of Canadian Shield
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In what country were these oldest dated rocks recently discovered?
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Australia. 4.2 billion years.
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Which of the three major types of plate boundaries is responsible for most orogenesis?
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convergent plate boundaries
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What is the difference between a shield and a craton?
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Shield is exposed portion of Craton
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What is the name of the complex mountainous region which extends through N. America from Alaska into Central Mexico?
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Cordierllan
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Continents grow and evolve by addition of felsic and mafic crust. A process known as:
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Accretion.
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The following have become microplates:
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island arces, ocean ridges, seamounts, fragments of other continents
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The micoplates identified on the west coast of N. America have been accreted within the past
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200 million years
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True or False.. An important means of continental accretion is plutonism
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True.
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what is a shield, such as the canadian shield?
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rge area of exposed Precambrian crystalline igneous and high–grade metamorphic rocks that form tectonically stable areas. VERY OLD!!!
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What are microplates?
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Small, continental like plates.
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What is the difference between horst and grabens?
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refer to regions that lie between normal faults and are either higher or lower than the area beyond the faults. Horsts of the higher than Grabens.
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What is the distinction between the hanging wall and the footwall of a fault?
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the hanging wall occurs above the fault plane and the footwall occurs below the fault
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What is a fault scarp?
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small step or offset on the ground surface where one side of a fault has moved vertically with respect to the other. Basically, a cliff.
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A rock which behaves as a brittle solid near the surface may behave in a ductile manner and deform (BLANK) under higher (BLANK) and pressures, and thus will (BLANK) instead of fracture
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,fold
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What are the names of the plates on either side of the plate boundary which passes through the state of California?
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North American plate and the Pacific plate
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Which type of plate boundary runs through the state of California and what is its name?
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–Strike slip fault
–San Andres Fault |
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Name its plate boundary:
The Himalayan and Tibetan Plateau |
Convergent
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Name its plate boundary:
The central and southern coast of California |
Transform
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Name its plate boundary:
The Gulf of California |
Divergent
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Name its plate boundary:
The Red Sea |
Divergent
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Name its plate boundary:
The Gulf of Aden |
Divergent
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Name its plate boundary:
The Alps |
Convergent
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Name its plate boundary:
The Philippine Islands and Japan |
Convergent
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Name its plate boundary:
Java and Sumatra |
Convergent
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Name its plate boundary:
The Aleutian Islands |
Convergent
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What happens when two continents converge?
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Doubling of the continent
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What happens at oceanic– continental
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What is the source of the material which is melted and later erupted at island arc volcanoes?
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Basalt and Coral
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Where do island arcs form?
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Oceanic convergent zones
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Give a example of a back–arc basin.
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Sea of Japan
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What are the two types of divergent boundaries?
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Oceanic spreading zones and continental riff zones
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Give an example of a long narrow sea which has formed over a divergent boundary, as a result of continental rifting?
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Red Sea
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In the plate tectonic model, what three kinds of boundaries can there be between adjacent plates?
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Convergent, Divergent, and Sheer zones
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How do geologist locate the boundaries of the plates?
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Earthquake activity
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Explain the differences of continental drift and plat tectonics.
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Continental (old) – shows how continents drift around.
Plate Tectonics (new) – How plates react |
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Where is new crust formed?
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Spreading zones, riff zones, and hot spots
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What is believed to be the mechanism for plate movement?
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Convection combined with gravity
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What is an orogen?
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Mountain building process
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What does the topography of the ocean floor actually consist of?
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Ridges, trenches, hills, vast plains, plateaus, and volcanoes
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What are turbidity currents?
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Undersea landslides
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Name the continental margin:
It's deeper edge lies at an average of 135 M |
Continental slope
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Name the continental margin:
It is cut by many deep ,steep sided canyons |
Continental shelf
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Name the continental margin:
It slopes Seaword at 2 to 4 on averages, sometimes as much as 25 |
Continental slope
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Name the continental margin:
Changes in sea level drown and expose this portion |
Continental shelf
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Name the continental margin:
Contains glacial sentiments, fossil mammoths, trees and archeological remains |
Continental shelf
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Name the continental margin:
Sedimentation here is affected by waves and tides |
Continental shelf
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Name the continental margin:
Sediments here are largely deposited by turbidity currents |
Continental rise
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What are three of the characteristics of an active continental margin?
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Small continental shelf, trench, abisel point
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What is an example of an active margin, in the Western Hemisphere?
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Chille
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Name it's geographic region:
East coast of south America |
Passive margin
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Name it's geographic region:
Region between the north Atlantic spreading ridge and the continental shelf of the United States |
Abyssal plains
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Name it's geographic region:
Offshore of the continental shelf of western South America |
Active margin
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Name it's geographic region:
The regions offshore, and east of, Japan and the Philippines islands |
Active margin
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Name it's geographic region:
The region offshore, south of the Aleutian Islands |
Active margin
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Name it's geographic region:
The region offshore of, and surrounding great Britain |
Passive margin
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Name it's geographic region:
The region south, and offshore of, Sumatra and Java |
Active margin
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Name it's geographic region:
The feature containing the deepest site in all the oceans |
Oceanic trenches
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Name it's geographic region:
The region off the coast of Southern California |
Passive margin
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What is an ophiolite
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A igneous rock consisting largely of serpentine
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