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geology midterm 1
Terms in this set (96)
What does "present is the key to the past" mean?
understanding the present events and processes helps to unravel the past history of our planet.
Natural systems are...
complex dynamic system always trying to reach equilibrium
The crust, the outermost layer of Earth, consists of...
continental and oceanic types
Plate tectonic theory is considered a unifying theory because it...
explains evidence for a dynamic Earth from a variety of subdisciplines and features in geology
The evidence supporting the "Big Bang" theory includes....
1. an expanding universe as evidenced by 'red shift'.
2. a pervasive background radiation everywhere in the universe
Mercury, Venus, Earth, and Mars have solid rocky interior and are called...
The age of the earth is established by dating the...
Increase in temperature of the early earth was caused by...
1. Meteoritic impacts
2. Gravitational compaction
How is Earth unique among the planets of our solar system?
Earth supports life, has oceans of water, has a hospitable atmosphere, has a variety of climates.
In addition to a hospitable atmosphere and climates, what are other favorable conditions for life's existence
on Earth that we know?
the presence of water, low levels of carbon dioxide
Give two examples of geology-related environmental concerns and briefly explain why geology holds the
focal position of environmental science?
water quality and distribution, soil formation and erosion. Geology concerns all aspects of the physical
Earth and their interactions with the biosphere.
What is one way in which geologic knowledge is used to help humans?
finding mineral or energy resources/helping solve environmental problems/predicting natural hazards
How have geologic natural resources been important in history?
States, nations, empires have risen and fallen because of, and fought for control of, natural resources
Give one specific example of how geology has an effect on your daily life in terms of materials and energy
Coal is used in producing steel and other materials, and supplies an increasing percentage of our
Give one example of how you might use geology as you prepare to purchase property on which to build
two of the most common natural hazards that affect homeowners are landslides and floods.
What was the origin of the material which now forms the solar system, according to a current theory?
Interstellar material in a spiral arm of the Milky Way Galaxy, which condensed and collapsed.
By how long ago had the early Earth formed?
4.6 billion years ago
Why is Earth considered to be a dynamic (as opposed to static) planet?
Earth has been continuously changed through its 4.6 billion year existence.
What are the two types of crust?
Which of Earth's major concentric divisions forms the largest volume?
The lithosphere is comprised of which layer or layers?
the crust and the underlying upper mantle
What are the three zones into which the mantle can be divided, based on physical characteristics?
solid inner mantle, plastic asthenosphere, solid upper mantle
Given that the asthenosphere behaves like a plastic, deforming under high pressures and temperatures,
explain why oceanic crust always occurs at lower elevations/greater depths than continental crust.
Oceanic crust is denser than continental crust and both "float" at equilibrium levels on the deformable
Briefly explain the differences between hypothesis and theory.
A theory is a systematic, broad-scope explanation consisting of one or more hypotheses that have
been or can be tested and that provide predictions that permit verification or rejection. A hypothesis is an
untested explanation of incomplete scope, from which there may or may not emerge verifiable predictions.
What fact about scientific theories best distinguishes science from other forms of human inquiry?
Scientific theories are always subject to further testing, which may result in their being supported or
What discovery, near the turn of the century, led to the development of techniques for determining absolute
ages of rocks in years?
What is the basic premise of the principle of uniformitarianism?
Present-day processes have operated throughout geologic time.
What are the two fundamental phenomena that are taken as evidence for the Big Bang origin of the
The galaxies are all moving away from one another, and there is a universal background radiation
slightly above absolute zero.
Name the terrestrial planets.
Mercury, Venus, Earth, Mars
Name the Jovian planets
Jupiter, Saturn, Uranus, Neptune
How do the Jovian planets differ from the terrestrial plants?
The Jovian planets are large and have low mean densities, and are composed largely of gases and
The deepest drill holes extend to approximately...
Discontinuities in earthquake (seismic) wave travel pattern permits...
1. the identification of internal layering of earth
2. the identification of rocks having differing compositions and properties.
Which one of this is the thickest internal layer of the earth?
The S-wave shadow zone exists because...
S waves do not travel through liquids
On average, Earth's lithosphere is approximately ____ km thick
Lithosphere consists of...
Upper mantle and crust
Continental Drift theory was proposed by...
The theory that finally explained the mechanism of continental drift was initially called...
Seafloor spreading theory
Mohorovicic discontinuity establishes the boundary between...
Crust and Mantle
Summarize the Uniformitarianism theory of James Hutton
Present is the key to the past
The mid oceanic ridges....
1. spans through the middle of most oceans.
2. are locations of numerous earthquakes.
3. are locations of rifts within the crust
Why are science fiction tales of subterranean journeys, such as Jules Verne's A Journey to the Center of
because of the intense heat and pressure
What is the major source of information used in developing this model of Earth's interior?
What are two ways in which the direction of travel of seismic waves can be changed as they travel through
by refraction and reflection
How are discontinuities located?
by marked changes in the velocity of seismic waves as they cross them
What are the major elements comprising Earth's core?
iron and nickel (and probably sulfur and other elements in minor amounts)
What is the asthenosphere?
a low velocity zone in the upper mantle where the rocks are close to their melting point and are thus
Is Earth's mantle entirely molten? What evidence is there?
No. S-waves are transmitted through the mantle.
Why do geophysicists believe the outer core is liquid?
S-waves, which do not travel through liquids, are completely blocked by the core.
Where is the continental crust thickest?
beneath mountainous regions
Where is the continental crust thinnest?
in regions of rifting
Where is the oceanic crust thinnest?
in regions of sea-floor spreading, or mid-ocean ridges
What is the primary source of Earth's internal heat?
the decay of radioactive isotopes
Although experts do not fully understand how Earth's magnetic field is generated, what appears to be the
best explanation for the field?
The Earth's magnetic field appears to be generated by electrical currents in the liquid outer core.
Hot material flows upward and displaces cool material.
Continental crust is ________ oceanic crust.
less dense than
In plate tectonic theory, the lithosphere...
1. is composed of oceanic and continental crust and upper mantle.
2. rests upon the buoyant asthenosphere.
3. is destroyed as fast as it is created.
At divergent plate boundaries, the forces operating are...
The currently accepted hypothesis for the driving mechanism of plate tectonics is based on...
thermal convection cells in the asthenosphere and mantle
Not evidence of continental drift theory
Presence of Kangaroos in Australia
Not associated with convergent plate boundaries
sea floor spreading
New lithosphere is created...
at mid-ocean ridges
When a deep-sea trench is located next to a continent, where would you expect to find active volcanoes?
on the continent side of the trench
an example of a transform plate boundary?
the San Andreas Fault
In which ocean are most of the world's convergent plate margins located?
Which ocean does the Ring of Fire encircle?
For what kinds of geologic activity is the Ring of Fire known?
intense seismicity, volcanism
In what way does plate tectonic theory have economic applications?
It can be used to predict the locations of natural resources, such as ore deposits
What are the lines of evidence which were cited for continental drift?
the glacial deposits of Gondwana continents, the fit of continental shorelines, fossil plant and animal
distributions, similar rock sequences and mountain ranges
Name a freshwater or land-dwelling reptile which was considered important fossil evidence linking the
Mesosaurus (freshwater)/Lystrosaurus /Cynognathus (both land-dwelling)
Early paleomagnetic data gathered in Europe showed the paleomagnetic north pole apparently wandered
with respect to Europe through time. What are three ways in which this data could be interpreted?
(1) the magnetic pole moved while the continent stayed fixed, (2) the magnetic pole remained in one
location and the continent moved, (3) the magnetic pole and the continent both moved over time
Who proposed the hypothesis of sea-floor spreading?
Harry H. Hess, 1962
What was the major difference between sea-floor spreading and continental drift?
with sea-floor spreading, continents don't move across or through oceanic crust, but rather the
continents and oceanic crust move together as parts of large plates.
What does the symmetrical pattern of magnetic polarities about spreading ridges in oceanic crust basalts
New ocean crust is created by volcanism at oceanic ridges and old crust moves laterally away from the
What evidence is there that the ocean basins are young and old ocean crust must somehow be destroyed?
The maximum age for oceanic crust is 180 million years, but the continents contain rocks much older
than 180 million years.
Briefly explain the mechanism of convective heat transfer.
When a material is heated, it expands, and its density decreases in comparison to the surrounding
colder material. Because its density is decreased, it rises. After having risen some distance, it begins to
cool, contract and become more dense. As its density increases, it sinks, and returns to the original level
where it will eventually become heated again.
Briefly describe the meaning of the term "plate" in "plate tectonic theory."
rigid independent sections of lithosphere which move about on the surface of the asthenosphere and
interact along their boundaries
Briefly describe the role of plate tectonics in geological processes:
Convergence, divergence, and transform movement of plates cause faulting, folding, earthquakes,
mountain building, and volcanism. Subduction results in partial recycling of crust to mantle.
Briefly describe how the discovery of sea floor spreading transformed the continental drift hypothesis into
the theory of plate tectonics.
Sea-floor spreading demonstrated that new crust was continually being formed and that continental
and oceanic crust moved together as a unit or plate in response to the forces that cause sea-floor spreading.
Who proposed the hypothesis of continental drift, and when?
Alfred Wegener, 1912
After Wegener's hypothesis of continental drift was rejected, what later hypothesis was proposed to explain
new data obtained from studies of the ocean floors?
How do geologists locate the boundaries of the plates?
In the plate tectonic model, what three kinds of boundaries can there be between adjacent plates?
(in any order) divergent, convergent, transform
At which type(s) of boundary(-ies) can we expect to have volcanoes?
divergent , convergent
At which type(s) of boundary(-ies) do we have earthquakes?
What are the three types of convergent boundaries?
continent-continent, continent-oceanic, oceanic-oceanic
Where do volcanic island arcs form?
at oceanic-oceanic plate boundaries
What happens at oceanic-continental convergent plate boundary?
subduction of the oceanic crust beneath the continental crust, with the formation of a volcanic arc on
the continental plate
What happens when two continents converge?
One of the continental plates will be incompletely subducted and a mountain range will form at the
What are the names of the plates on either side of the plate boundary which passes through the state of
Pacific Plate, North American Plate
What are hot spots or mantle plumes?
sites within plates or along their boundaries where stationary mantle plumes rise to the surface
Why are hot spots considered useful for determining the absolute motions of plates?
The hot spots appear to be essentially fixed in position, so they can be used as a reference frame
Which of the following are all examples of minerals?
copper, ice, quartz, topaz, diamond,
Minerals originate from crystallization of...
1. molten magma
2. hydrothermal solutions
4. chemical alteration of pre-existing minerals
Which group below lists the elements in correct order of abundance in the earth's crust
O, Si, Al, Fe
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