Geology Midterm
To show topography in a flat coastal area, the most appropriate contour interval would be
5 feet
What must be true in order for an ore mineral occurrence to be economically viable?
All the possible answers are correct- concentrated elements greater degree than average crystal abundance; enough ore mineral to make extraction profitable; sale price of element must be greater than costs of mining and extraction
The Public Land Survey System is used in all of the following states except
Massachusetts
Which of the following physical properties will change when you break a mineral into smaller pieces?
None of these properties will change despite how small the specimen becomes.
What changes take place during physical weathering?
Rocks are broken into smaller pieces.
What changes take place during chemical weathering?
The mineralogy of previously existing rocks
Magnetic anomaly "stripes" in the ocean are caused by
a combination of the Earth's current magnetic field and ancient magnetic fields at the time oceanic rocks are formed
Shear stress is what is generated when we use which of the following tools?
a pair of scissors
A seamount forms when
a volcano is eroded by waves and sinks as it becomes denser with time
Sedimentary rocks are formed in horizontal layers called
beds
In what ways does the formation of sedimentary rocks differ from that of a sedimentary rock or igneous rock?
changes from the previously-existing rock from which it forms all take place in a solid state
Geologists classify minerals into groups like silicates by their
chemical composition.
Biogenic sedimentary rocks are similar to ________ in that __________.
chemical sedimentary rocks; removal of dissolved ions from water is a very important process in their formation
What is the result when some of the chemical bonds in the minerals are stronger in some directions than in others?
cleavage
Grain size generally increases wit metamorphic intensity except in
dynamic metamorphism
The latitude and longitude is based on the
equator
The increase of temperature with depth within the Earth
is caused by the geothermal gradient.
Meridians of longitude
meet at North and South Poles
orders of magnitude
scientific notation (powers of 10)
The zero contour line is also known as
sea level
The texture of a rock includes its constituent grains
size, shape, and orientation
In making scale models to understand the Earth, the one factor that cannot be scaled down is
time
The agents of metamorphism include all except which of the following?
time
Which property of a protolith may change during metamorphism?
all of the possible answers are correct - grain size, grain shape, mineralogy
What can the formation of sedimentary rocks involve?
all of the possible answers are correct - precipitation of minerals when water evaporates; consolidation of many shells; transportation of fragments of rock weathered from previously existing rocks
biosphere
realm of living organisms
Strike and dip refer to
the orientation of a bed or fault
Why is vertical exaggeration often used on maps and map profiles?
to make topographic features like hills and valleys more visible
hydrosphere
water
On a map with a scale of 1:48,000, a distance of 1 mile would be represented by how many inches?
1.32
To show topography in a rugged, mountainous area, the most appropriate contour interval would be
100 feet
geosphere
solid earth
The texture of a rock is controlled by
the process of which it forms
You have been asked to draw a map of a part of your campus on a 8.5x11 sheet of paper. You first try a scale of 1:1,000, but the paper is not large enough. Which of the following scales might work better?
1:5,000
Which of the following is a possible origin of a metamorphic rock?
A sedimentary rock is buried deeply beneath other sedimentary rocks.
Sedimentary rocks are unique in that they form
by processes that operate at or near the Earth's surface
A good map must contain a way to accurately determine which of the following?
all of the possible answers are correct - distance between points shown on map, directions between points shown on map, location of points shown on map
A theory is
an explanation that has been tested many times and shown to be correct in all tests
Solidified lava flows and volcanic ash deposits are examples of
extrusive igneous rocks
The release of oxygen by green plants during photosynthesis is an example of
flux involving the biosphere and atmosphere
What causes the steep slope of stratovolcanoes (composite cones)?
large volumes of hot tephra that weld to one another
Which of the following physical properties of a mineral depends on the strength of the bonds that hold its atoms and ions together?
luster
Every mineral has a preferred habit (crystal shape) but most mineral grains do not display that shape because
many grains interfere with one another while they are growing.
in identifying rocks, geologists must consider its
mineral content and texture
foliation and lineation are terms that describe
the orientation of minerals in metamorphic rocks
At what type of plate boundary is there no vertical transfer material between the lithosphere and the asthenosphere?
transform fault
Where is the large-scale shear stress model found in the plate-tectonics model?
transform faults
A porphyritic texture indicates that the cooling rock had
two different cooling rates
Fault-block motion in a dip-slip fault is
up and down the fault plane
Contour lines on a topographic map
are usually brown
Well-rounded grains in a clastic sedimentary rocks indicate
numerous collisions between particles during extensive transportation
scientific method
observation, collecting data to ensure observation valid, hypothesis, test hypothesis
Earthquakes occur frequently at
ocean ridges, subduction zones, and transform faults
In the tectonic cycle, new lithosphere forms at ______ and is consumed at _______
ocean ridges; subduction zones
Contour lines on maps connect points
of equal elevation
In an anticline, the __________ rocks are exposed in an axial region of the fold, and beds typically dip __________ one another.
oldest; away from
Metamorphic foliation produced during compression will be
perpendicular to the compressional stress
Angular grains in a clastic sedimentary rocks indicate
rapid, typically short-distance transport
rocks forming today
recycle materials from previously existing rocks
Collision of two continental plates would cause
regional metamorphism
Igneous rock forms by
solidification of magma at the surface or within the Earth
The difference between a plunging and non-plunging fold is that
the hinge of the plunging fold is not horizontal.
Polymorphs (minerals like diamond/graphite with same chemical composition but are different minerals) exist because
their mineral structure differs based on the different temperature and pressure conditions under which they are formed.
Which of the following is LEAST likely to be associated with the eruption of a shield volcano?
a pyroclastic flow (nuee ardente)
Earth's internal structures includes
concentration of the densest materials in the Earth's core.
When the chemical bonds in a mineral are equal in all directions, what will the result be?
conchoidal fracture
Small tick marks (hachures) on contour lines indicate
depressions
what is true clastic sedimentary rock
mineral grains can come from many previously existing sedimentary rocks
A vertical exaggeration of 1.00x on a topographic profile means
the vertical scale of the map is the same as the map scale
Base lines and principal meridians are reference lines to the
township and range (Public Land Survey)
In a syncline, the ______ rocks are exposed in an axial region of the fold and beds typically dip ______ one another
youngest; towards
A benchmark is
a permanent marker on the ground that indicates location and elevation
A hypothesis is
a tentative explanation for a natural phenomenon or Earth material
Earth System
all Earth's materials - gases, liquids, solids, and life forms hy
Mohs hardness scale describes the relative hardness of ten minerals, not their absolute hardness. This means that
diamond will scratch talc, but talc won't scratch diamond
A direction of 315 degrees in the azimuth system corresponds to
northwest
Two maps have been drafted so that each fills a sheet of 8.5x11 paper, one at a scale of 1:24,000 and the other at a scale of 1:62,500. Which of the following statements correctly describes the map?
The map with the scale of 1:62,500 covers more area than the other.
What does the term metamorphic grade refer to?
the degree to which a metamorphic rock's protolith has changed
The eastern edge of the North American continent is not the same as the eastern boundary of the North American plate. The eastern edge of the North American continent is
the edge of the continental shelf because that is where the continental crust ends and oceanic crust begins
The presence of footprints in a sedimentary rock is compatible with the origin in all of the following environments except:
the floor of the Atlantic Ocean
What are the latitude/longitude and UTM systems used to describe?
the locations of points on a globe
The presence of tropical plants and animals hundreds of millions of years near the North Pole suggest that
the plate on which those organisms are found has moved from a different climate zone to its current Arctic position
The principle of uniformitarianism is
the present is the key to the past
The grain size of an igneous rock is determined primarily by
the rate of cooling, which controls the amount of time ions have to migrate the crystal seeds
Metamorphic index minerals help geologists determine
the temperature and pressure conditions during metamorphism
The asthenosphere is:
a layer of low rigidity that separates the rigid lithosphere from the rigid mantle
What is true of map projections?
all possible answers are correct - they needed to portray the nearly spherical of the Earth on a flat page; may significantly distort the shapes of continents and oceans; can be selected so that they show particular aspects of a landmass most accurately
What do lines separating different rock units on a geologic map represent?
all the possible answers are correct - faults, stratigraphic contacts between sedimentary formations, intrusive contacts between plutons and their host rocks
The Himalayan Mountains formed when
an ocean that once separated India and Asia closed by subduction
cryosphere
frozen water, including snow
Why is the scientific study of our planet difficult?
All possible answers are correct; - (1) Earth's size is relative to humans is much greater that it is so hard to conceive the scale of some of its processes (2) Many of the processes responsible for forming some of Earth's features can be so slow we cannot detect them (3) Earth history extends more than 4.6 billion years into the past
At which locations is volcanic activity abundant?
Volcanic activity is found at all of these locations - ocean ridges; subduction zones;
What does a map scale of 1:24,000 describe?
a map where 1 inch corresponds to 2,000 feet on the ground
Which rock transformations can occur in a rock cycle?
all of them - igneous-sedimentary; metamorphic-sedimentary; sedimentary-sedimentary
Which of the following describes the formation of chemical sedimentary rocks?
all of these describe the formation of chemical sedimentary rocks - their minerals form a crystalline texture; their minerals form by precipitation of ions from water; their minerals form from ions dissolved from previously existing minerals during chemical weathering
Which of the following shows the topography of a landscape?
all possible answers are correct - a digital elevation model; a Landsat satellite image; a contour map
The absence of preferred orientation in minerals in metamorphic rock may be due to which of the following?
all possible answers are correct - lack of stress during metamorphism; absence of platy minerals like mica; absence of rod-shaped minerals like amphibole
The presence of water
all possible answers are correct - lowers melting temperature during flux melting; helps magma rise towards surface; causes explosive volcanic eruptions
Why is quartz one of the most abundant minerals?
all possible answers are correct - made up of two most abundant materials; resistant to weathering; can form in igneous, sedimentary, and metamorphic rocks
Formation of large grains in an igneous rock is aided by
all possible answers are correct - magma with low viscosity, very slow cooling, and the presence of water in magma
What does a map scale of 1:24,000 indicate?
all possible answers are correct - one inch on map equals 24,000 inches; one centimeter on the map equals 24,000 centimeters on the ground; one foot on the map equals 24,000 feet on the ground
What does the assemblage of minerals in a metamorphic rock help to determine?
all possible answers are correct - the chemical composition of a protolith; the temperature at which metamorphism took place; the pressure at which metamorphism took place
Which of the following might clastic sedimentary rocks contain?
all these types of clasts - individual mineral grains separated from previously existing rocks during weathering; rock fragments made up of several minerals; fragments of volcanic glass
Most of Earth's volcanic and earthquake activity occurs
at the edges of lithosphere plates
Block diagrams used to portray geologic structures contain
both of the possible answers are correct - a map view, two cross-sectional interpretations
A fine-grained texture most likely formed when a magma cooled
close to the Earth's surface
The lithosphere is
composed of the entire crust and uppermost mantle
Intrusion of granite into layers of sedimentary rock would cause
contact metamorphism
In the plate-tectonic model, where is the large-scale compressional stress found?
convergent plate boundaries
__________ occurs at ocean ridges, whereas _______________ occurs at subduction zones
decompression melting; flux melting
Mineral assemblages generally become ______ the deeper in the Earth that metamorphism takes place
denser
Where is large-scale tensional stress found in the plate-tectonic model?
divergent plate boundaries
Isotherms on weather maps differ from contour lines on topographic maps in that they
do not show changes in elevation
The interaction of plates on opposite sides of a transform fault results in
dynamic metamorphism
Which of the following map elements is not shown on an aerial photograph?
elevations and slope steepness
The Earth's magnetic field
generates lines of force that run parallel to Earth's surface at the equator
In the Earth concept, minerals and rocks are found in the
geosphere
The principle of uniformitarianism is most useful for interpreting most ancient geologic events except those that
happened early in Earth history and do not occur today
Glassy igneous rocks
have no minerals
A mineral may have a high specific gravity because its atoms are either ________________ or ________________
high in atomic mass; packed closely together
The relative motion of fault blocks on opposite sides of a strike-slip fault is
horizontal
a glassy texture is most characteristic of
igneous rocks
Quartz is not a good index mineral because
it is stable over a very wide range of temperatures and pressures
The longitude of a location is based on the
prime meridian
Most fossils are found in sedimentary rocks because
sedimentary rocks form in the same environment where the plants and animals lived and died
The difference between sills and dikes is that
sills are parallel to layering in surrounding rocks while dikes cut out layering
all of the following properties of a mineral can be observed/measured when a mineral is found in a rock, EXCEPT its
specific gravity
Where are the intermediate igneous rocks (andesite and diorite) most commonly found?
subduction zones
The uplift of new mountains and the erosions of old ones
take place over millions of years
Which of the following mineral properties is chemical rather than physical?
taste
The major source of energy that melts the rock within the Earth, causes earthquakes, and builds mountains comes from
the Earth's internal heat
The eastern edge of the North American plate is
the Mid-Atlantic Ridge, because that is where seafloor spreading takes place.
Information on the borders of the topographic map includes all except
the types of rocks present in the map area
Cross-bedding and ripple marks are the result of ________ during deposition.
water or wind currents
A mature clastic sedimentary rock is characterized by what properties?
well-rounded grains, good sorting, and minerals resistant to chemical weathering
Volcanic arcs form above subduction zones
wherever oceanic lithosphere is subducted
