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test bank 3 geology
Terms in this set (87)
what was the last eruption in the us
1980 mt. st. helens
what are the two types of eruptions? what are their characteristics and examples?
- normally mafic
- intermediate and felsic lava
- ex: Mt. St. Helens
why are some volcanoes quiet and some explosive?
what is viscosity?
measure of how easily fluids flow
-high- pasty, explosive, felsic
-low-watery, quiet, mafic
how does viscosity cause explosive volcanoes?
high viscosity magma clogs the piping system, then gases (mostly steam) build up in magma chamber and explodes
what are the two types of lava and their textures?
pahoehoe- ropey, smooth
aa- angular, jagged blocks
what are the three different types of volcanoes
sheild, composite, and cinder cone
what is a shield volcano and example?
-tallest volcano on earth
-broad and wide
-basaltic lava (low si, so low viscosity)
what is a composite volcano? example
-large volcanoes about 8,000 ft
-classic volcano shape, concave upward slopes 15 degrees at base 30 degrees at top
-mostly intermediate compositions
-lava flows mixed with pyroclastic eruptions
-example: mr. st helens
soft, easily eroded
a fiery cloud that is deadly, superheated with pyroclastic flow
-greater than 800 degrees c
-clocked at 100 mph
-killed maurice and katia kraft
what is a cinder cone volcanoe?
-smallest type of volcano
-very steep slopes (30-40 degree)
-only pyroclastic material
- a lot of times they are subsidary structures on the sides of larger volcanoes
what is a fissure eruptions? why is it not its own type of volcano?
from a fissure/fracture
-there is no volcanic cone
-very low viscosity, basaltic lavas
water like, called flood waves
what is a fold shaped like an elongated trough
what is a fold shaped like an elongate arch
what is a fold shaped like an upside down bowl
fold shaped like right side up bowl
what is a polished surface produced by scraping of rock along a fault
what are normal, reverse, and thrust examples of
what is the change in shape, induced by stress called?
when a body of rock affect by tensile stress will likely undergo
during deformation, rocks can undergo a change in all of the following except
can large scale volcanic eruptions cause a drop in global temperature
what is the hawaiin island chain an example of
hot spot island chain
whether an eruption will primary produce lava flows or pyroclastic debris is influenced by the
viscosity of the lava, composition of the lava, and the proportion of gases within the lava
do all volcanic eruptions pass through the crater at the volcanic summit?
which of the three primary forms of subariel volcanoes consist of alternating layers of tephra and solidified lava?
which are true about pahoehoe?
a. forms when a basaltic lava flow ceases flowing and solidfies simultaneously
b. has a smoother texture than a'a'
c. is easier to walk on than a'a
all of the above
basaltic lavas that solidify at their surface (before ceasing to flow) that fracture irregurlary, producing a sharp surface lava rock called_________
in 79 CE the citizens of pompeii in the roman empire were burried by pyroclastic debris derrived from an eruption from _______
in an undisturbed sequence of sedimentary rocks, younger layers overlay old layers according to what principle?
the surface below sedimentary rocks that overlie igneous or metamorphic rocks is termed
buried erosional surfaces between parallel sedimentary strata are termed
uniformitarianism is succintly summarized by which phrase
the present is key to the past
a body of rock affect by compressive stress will likely undergo
the central portion of high curvature on a fold is termed the fold
in a __________ fault, the hanging wall block moves downward relative to the foot wall
on a geologic map, if the contacts form a cirlce, with the youngest rocks in the center, they underlying structure is a
on a geologic map, if the contacts form a circle, with the oldest unit in the center, the underlying structure is a
the below figure would be considered to have what type of rotational stress (shear)
sinistral (left handed, anticlockwise)
<--- is clockwise or dextral (right handed)
concerning the relative ages of the shale and sandstone,
shale must be older according to the principle of superposition
basaltic clasts within the conglomerate have been radiometrically dated to 50 million years ago. is this a reliable age for the conglomerate?
no this age is likely too old
concerning the relative ages of the basalt and the fault,
basalt must be older according to the principle of cross cutting relationship
the basalt body is best described as a
earthquake waves that pass through the interior of earth are termed
what are the two types of body waves?
s and p waves
the point within earth where an earthquake takes place is termed
hypocenter or focus
the smoky cloud that rises from the vent of an actively erupting volcano is composed of
fine volcaniclastic debris (ash) suspended in the air
contain more iron and MG than rhyolite lavas
of the three primary forms of volcanoes ________ are the larges in area
of the three primary forms of volcanoes, _________ have the most gently sloping slides, due to the low viscostiy of the basaltic lavas which form them
of the three primary volcaones_________ consist of a simple conical pile pf tephra
of the three primary forms of volcanoes, _________ consist of alternating layers of tephra and solidified lava
mt. fuji in japan is an example of a
the hot spot track associated with the hawaiian islands and emperor seamounts
shows that the pacific plate has been moving northewst for the last 30 million eyars
at continental rifts, vast bodies of basaltic lava flow forth from fissures, forming
which national park is home to a large volcanic caldera formed through a very large explosive erruption 630,000 years ago
if during an earthquake, a hanging wall slides upward relative to a football, the fault is termed ______ if the fault is steep (closer vertical than horizontal) ( fualt plane is greater than 30 degrees from horizontal)
if during an earthquake a hanging wall slides upward relative to a footwall, the fault is termed ______ if the fault is shallow (much closer to horizontal than vertical) (less than 30 degrees from horizontal)
if during an earthquake a foot wall slides upward relative to a hanging wall the fault is termed or the hanging wall block moves downward relative to the foot wall block
if a fault is nearly vertical in orientation and the two walls of rock on opposite sides slide past one another horizontally, the fault is termed
faulting and earthquakes are examples of
which type of earthquake waves generally travels fastest
body waves (p wave)
which waves cause most of the damage to building during earthquakes
the point on earths surface directly above the point where an earthquake occurs is the
how many siesmic stations are necessary to find the epicenter of an earthquake
which earthquake intensity scale assesses the effects of an earthquake on humans and human made structures
earthquakes are likely to occur along
all three major types of plate boundaries
intermediate and deep earthquakes occur along
convergent plate boundaries only
a tsunami is
an earthquake generated sea wave that can sometimes destry coastal cities thousands of kilometers from its source
the distinction between joints and faults is that _______
faults are fractures along which displacement has occured, displacement does not occur along joints
james hutton the father of geology put forth the principle of
which proportion of a radioactive isotope is expected to remain in the parent state after the passage
in what tectonic setting would you expect to find horsts and grabens?
in what tectonic setting would you expect to find reverse faults?
basaltic clasts within the basal layers of the conglomerate imply which of the following statements
the basalt must be the older of the two
the secction must not have been overtuned by tectonic activity at any time
numerical ages for boundaries between time units on the geologic time scale primarily resulted from the study of _____________, in conjuction with relative age data
radiometric dating of igneous rocks
if the relative age of two formations (with respect to one another is known,) then the numerical ages for each formation can be inferred
which statement best summarizes the development of the geologic time scale
relative ages for sedimentary strata were konwn well before accurate numerical dates for these rocks could be provided
if the lithology and fossil content of two bodies of rock on opposite sides of a cnayon are identical, even these remaining outcrows were likely physically connected at one time and formed for of an extensive, sheet like layer rock. this idea summarizes the principle of
as understood by modern geologists, the prinicple of uniformitarianism impoles that
physical processes oberserved today (such as erosion and volcanic eruptions) have been active in the past and are responsible for the geollgic history we see preserved in rock record
radiometric dates applied to the sedimentary rocks produce ages that are
too old (pre date sed deposition)
which of the following geologic prinicples is a direct result of gravity
original horizontality the half
why is radiocarbon dating only rarely applied in geological work?
the half life of carbon 14 is so short that it can only be used to date materials that are less than 70,000 years old
if horizontal sedimentary strata overlie strate (and no fault is present) the surface between the hroiztonal and tilted strata must be an
which of the following geologic prinicples is NOT a result of gravity
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