80 terms

Geology Exam 2 Study Guide

Chapters 6, 7, 9 & 10
is the most common mineral in sandstones.
Compaction of sediment tends to
reduce the volume of pore space.
A cherty limestone contains which major constituents?
clay minerals
Which of the following best describes bedded gypsum and halite
evaporites (one type of chemical sedimentary rock).
is a sandstone contains abundant feldspar, suggesting that the sand was derived by weathering and erosion of granitic bedrock.
Iron oxide
is a sandstone contains abundant feldspar, suggesting that the sand was derived by weathering and erosion of granitic bedrock.
What is the main difference between a conglomerate and a sedimentary breccia?
Breccia clasts are angular; conglomerate clasts are rounded.
Which type of limestone consists mainly of tiny, marine fossils composed of calcite
is not a common cement mineral for sandstones.
Chert is a microcrystalline form of the mineral
Which of the following sedimentary rocks would you expect to have originally been deposited by fast-moving streams
Which of the following sedimentary features would typically be found in shales but not in sandstones?
mud cracks
Which one of the following is not a chemical sedimentary rock?
Which of the following is not a type of limestone?
Which of the following sedimentary features can each be used to determine paleocurrent directions?
current ripple marks
Coal beds are derived from plants that lived in
freshwater coastal swamps and bogs.
Clay and muddy sediments lithify to form shales and mudstones
Most marine limestones are of biochemical origin.
Mud cracks in a shale or mudstone indicate that the mud or clay was deposited in deep waters of an offshore marine environment.
Detrital sedimentary rocks are classified according to clastic particle size; chemical sedimentary rocks are named according to the most abundant minerals.
Of the following four rocks, which forms at the highest grade during regional metamorphism?
Which low-grade metamorphic rock, composed of extremely fine-sized mica and other mineral grains, typically exhibits well-developed rock cleavage?
Which of the following statements concerning slate is not true
has abundant, coarse-grained mica
is a planar fabric in a metamorphic rock due to a preferred alignment of platy or elongate mineral grains.
is a nonfoliated rock formed by contact metamorphism of a sandstone.
Which of the following best describes the conditions of contact metamorphism?
pressures are fairly low, the rock is in the upper part of the crust, and heat is supplied from a nearby magma body
forms from the metamorphism of limestone or dolostone.
What foliated, metamorphic rock is texturally intermediate between slate and schist?
fault breccia
Granitic gneiss
is characterized by the segregation of light- and dark-colored minerals into thin layers or bands.
Which metamorphic rock consists mostly parallel aligned coarse-grained, mica flakes?
Which of the following lists the rocks in the order of increasing grain size and increasing grade of metamorphism?
slate, phyllite, schist
Which of the following rocks is foliated?
What is the major source of heat for contact metamorphism
heat from a nearby magma body
A migmatite
forms at very high temperature and involves partial melting of rock as well as metamorphism.
Calcite is the main mineral constituent of the sedimentary rock limestone and of the metamorphic rock marble.
Metamorphic rocks formed during episodes of mountain building typically show textural characteristics indicative of shearing stress and deformation
Foliated metamorphic rocks are composed largely of equidimensional grains of minerals such as quartz and calcite.
Rock cleavage in slates (slaty cleavage) is largely a consequence of abundant, parallel-aligned, very fine-grained mica flakes in the rock.
The distinctive layers or bands of different minerals in gneisses may be complexly folded
High-grade, regional metamorphism produces significant and recognizable changes in the textures and mineral compositions of rocks.
How does urbanization (paving, etc.) affect runoff and infiltration in a small, previously forested, drainage basin?
infiltration decreases; runoff increases
Silt and clay-sized, detrital grains
make up the suspended loads of most rivers and streams.
At the head of a delta, the major channel splits into smaller channels that follow different paths to the sea. These smaller channels are known as
A radial
stream pattern is developed only on growing mountains like volcanoes or where the land surface is tectonically doming upward.
A trellis
stream pattern develops on lands underlain by tilted or folded, alternating hard and soft, sedimentary strata.
An oxbow
is an abandoned, cutoff, meander loop that is now a lake.
Rapids and lots of whitewater
are characteristics of downcutting streams and a youthful stage of valley evolution.
Many larger rivers in the Colorado Plateau region meander in deep, narrow canyons and have no floodplains. How could this happen?
meandering streams became rejuvenated, starting to downcut as the land gradually rose
The Amazon
has the largest discharge of any in the world.
Where is erosion concentrated along a meandering stream
on the outer parts of the meander loops or bends
Which one of the following would cause stream rejuvenation?
the land is uplifted
A stream begins at an elevation of 200 meters and flows a distance of 400 kilometers to the ocean? What is the average gradient?
Gradients usually decrease downstream in a major river system
Point bars are depositional features located along the outer portions of meander bends
Rapids and waterfalls are characteristic of laterally cutting (meandering) streams.
After a meander is cut off, the gradient through the newly formed cutoff is steeper than the gradient along the abandoned meander loop
Stream discharge is defined as the quantity of water flowing past a specific channel location per unit time
A V-shaped valley and no floodplain indicate a youthful, downcutting stream
Lateral cutting and deposition are important factors in floodplain development.
All else being equal, a stream with a boulder-strewn bed would be more turbulent than one with a sandy bed.
describes the ease of fluid transmission through rock.
The most useful aquifers for obtaining abundant groundwater possesses
high potability and high portability
A perched water table develops when
a horizontal aquitard above the regional water table lies below an aquifer.
An artesian well is one in
water rises above the top of the aquifer without any pumping.
Excessive groundwater withdrawals can cause
the water table to fall.
Which of the following geologic materials would have the highest groundwater velocities and be least effective in removing unwanted pollutants from the water?
limestone; numerous solution channels and fractures widened by dissolution
A stalactite
is the icicle-like speleothem that grows down from the roof of a cavern.
Which of the following can possibly contaminate an aquifer?
pesticides, industrial chemicals, sewage (all of the above)
The unsaturated zone of an aquifer
lies above the water table.
An aquifer is
a permeable rock unit that possesses a saturated zone.
Which of the following describes the configuration of an unconfined water table around a pumping well?
cone of depression
is the percentage of a rock or unconsolidated sediment that consists of empty space.
An unconfined water table is
the boundary between the unsaturated zone above and saturated zone below.
Which of the following best describes how geysers erupt?
with a slight reduction in pressure, water in a saturated, natural conduit suddenly boils, sending a plume of steam and hot water into the air above the vent
he water table is a surface separating the saturated and unsaturated zones.
In areas with humid climate, the water table of an unconfined aquifer generally slopes downward towards stream valleys.
Most caves and caverns originate by dissolution of limestone.
Water-saturated muds have low permeabilities but can have greater porosities than well-cemented sandstone
In areas underlain by unconsolidated or weakly consolidated strata, lowering of the water table can cause the land to subside
In general, contaminated groundwater will be naturally cleaned faster by circulation through porous and permeable sands than by circulation through fractured, crystalline igneous and metamorphic rocks