Geo Exam 2 All Homeworks
Quartz is not a good index mineral because
It is stable over a very wide range of temperatures and pressures
If a fault offsets a sequence of sedimentary rocks, what must be true about the fault?
It is younger than the rocks based on the principle of cross-cutting relationships
Define the principle of original horizontality
Layers of sediment, when first deposited, are fairly horizontal
Which mineral is responsible for the strong foliation in a schist?
Mica
Which of the four types of seismic waves are body waves?
P-waves and s-waves
Order the steps in neocrystallization
Protolith minerals are consumed by chemical reactions. Thin clay minerals begin to align. Clay grains flatten out and become parallel to one another. Small garnets appear.
Form of metamorphism occurring at a fault zone
dynamic
Foliation is an alignment of mineral grains ____________ to the direction of compression
perpendicular
A vertical exaggeration of 1.00x on a topographic profile means
the vertical scale of the profile is 100x that of the map scale
The agents that cause metamorphism include all except which of the following?
Time
The low seismic velocity zone is caused by
a change in the rigidity of the mantle in the asthenosphere
The two main types of sedimentary rocks are
clastic and chemical
Attributes of crustal deformation being associated with folding
compressional stress, bending of geologic materials, and ductile deformation
A sedimentary rock with large class sizes (>2mm) would be called a
conglomerate
Consequences of shear stress
elongation of grains; foliation
Chemical weathering is highest in
rocks that have been broken up by intense physical weathering
A disconformity occurs when
there has been some uplift and erosion but no folding between deposition of rocks above and below the disconformity
Which of the four types of seismic waves are surface waves?
R-waves and L-waves
Marble is metamorphic rock that was originally
Limestone
Which property of a protolith may change during metamorphism?
Grain size, grain shape, and mineralogy
To show topography in a rugged, mountainous area, the most appropriate contour interval would be
100 feet
The absence of preferred orientation of minerals in a metamorphic rock may be due to what?
The lack of stress during metamorphism, the absence of play minerals like mica, and the absence of rod-shaped minerals like amphibole
Metamorphic index minerals help geologists determine
The temperature and pressure conditions during metamorphism
The asthenosphere is known from
a low velocity zone in the upper mantle
Contour lines on a map connect points
of equal elevation
What is one difference between body and surface waves?
Body waves are described as compressional or shear.
The principle of superposition can be used to determine the relative ages of all of these
a sequence of lava flows, layers of unconsolidated sediment in a lake, and horizontal layers of sedimentary rock inter-layered with lava flows
Which of the following is NOT an example of a chemical sedimentary rock
breccia
Attributes of crustal deformation being associated with faulting
brittle deformation
Form of metamorphism occurring ten miles below the surface
burial
Small tick marks (hachures) on contour lines indicate
depressions
Which of the following processes is NOT important in generating the components necessary for the formation of sedimentary rocks
diagenesis
Compared to the average density of the mantle, the average density of the continental crust is
less
What tectonic processes are associated with earthquakes?
plate subduction, mountain building, formation of ocean basins, and movement along plate boundaries
The zero contour line is also known as
sea level
Long-term earthquake predictions are based on what?
seismic belts and recurrence intervals
Form of metamorphism occurring at a meteorite impact site
shock
Particle size is used as an indicator of maturity in clastic rocks. This is because
smaller particles have been transported farther and are therefore older
Glacial isostatic rebound refers to
the isostatic uplift of continental margins associated with meltwater induced sea level changes since the glacial maximum
The Moho is
the observation that seismic waves speed up below the crust mantle boundary in association with a compositional change
The face that the outer core is liquid is known from
the s-wave shadow
An angular unconformity is evidence that
there is an incomplete geologic record preserved in an area
Form of metamorphism occurring at a intrusion of a pluton
thermal
In order for a fossil to be used as an index fossil, the species must have existed for a
very short span of geologic time and lived throughout the world
The term relative age refers to
whether a feature is older or younger than another
What does the assemblage of minerals in a metamorphic rock help to determine?
The chemical composition of a protolith, the temperature at which metamorphism took place, and the pressure at which metamorphism took place.
What does the term metamorphic grade refer to?
The degree to which a metamorphic rock's protolith has changed
Foliation and lineation are terms that describe
The orientation of minerals in metamorphic rocks
What solid is most likely to deform elastically under stress?
a rubber band
The principle of inclusions states that
a sedimentary rock must be younger than the clasts that it contains
Which statement best agrees with the isostasy model of G.H. Pratt?
High elevation regions have lower-density crust than lower elevation areas.
Which statement best agrees with the Airy model for isostacy?
High topography regions have thicker crust than lower relief areas
Contours form closed loops around
depressions and hills
The two types of chemical sedimentary rocks are
inorganic, biochemical
To show topography in a flat coastal area, the most appropriate contour interval would be
5 feet
How is ductile deformation different from elastic deformation?
Ductile deformation ca result in tight folds, whereas elastic deformation usually terminates in brittle deformation rather than tight folding. Once the stress is removed, rocks that have undergone ductile deformation retain their new shape.
What types of deformation do rocks undergo during formation of an orogenic belt such as the Alps?
Faulting, folding, foliation, and jointing
What is true about earthquakes?
Most are the consequence of plate tectonics, an estimated 1 million occur each year, but most are small, and most occur along plate boundaries
Imagine a mountain range supported by a low-density root zone (Airy's hypothesis). What is the isostatic response as rivers erode the mountain away?
The mountains and root zone rise, and the mountains become lower as the root zone also diminishes.
A Wadati-Benioff zone is
a band of earthquakes along subducting lithosphere in a convergent boundary
A benchmark is
a permanent marker on the ground that indicates location and elevation
What is isostasy?
a state of gravitational equilibrium maintained by a block of lithosphere that "floats" in the underlying mantle at a level determined by both its density and its thickness
Consequences of uniform pressure
development of large, equant grains; rounding of grains
Form of metamorphism occurring at a mountain range core
dynamo-thermal
The Moho and the base of the lithosphere are the same
false
Immature sedimentary rocks can be distinguished from mature ones by greater amounts of
feldspar
Form of metamorphism occurring at a mid-ocean ridge
hydrothermal
Information on the borders of a topographic map includes all except
the types of rocks present in the map area
What type of unconformity forms when sedimentary rocks overlie either igneous or metamorphic rocks?
a nonconformity