Geology Exam 3
according to currently available geologic evidence, life appeared on the Earth about ___ ago
3.5 billion years
the oldest known rock found on Earth is dated at ___ years old
4.03 billion
formation of the earth beginning of the paleozoic era beginning of the mesozoic era end of the mesozoic era
4.5 billion years ago 541 million years ago 252 million years ago 66 million years ago
we live in the ____ epoch, the ___ period, and the ____ Era
Holocene quaternary cenozoic
faunal succession
William Smith's principle or law stating that fossil species succeed one another in a definite and recognizable order; in general, fossils in progressively older rock show increasingly greater differences from species living at present
inclusion
a fragment of rock that is distinct from the body of igneous rock in which it is enclosed
soil
a layer of weathered, unconsolidated material on top of bedrock often also defined as containing organic matter and being
cross cutting relationships
a principle or law stating that a disrupted pattern is older than the cause of disruption
disconformity
a surface that represents missing rock strata but beds above and below that surface are parallel to one another
flow
a type of movement that implies that a descending mass is moving downslope as a viscous fluid
talus
accumulation of broken rock at base of a cliff
numerical age
age given in years or some other unit of time determined by using radiometric dating
what are the ways the nuclei of radioactive isotopes can change
an alpha emission a beta emission electron capture
the event that may have caused the extinction of dinosaurs was ___
an asteroid impact on Earth
nonconformity
an unconformity in which an erosion surface on plutonic or metamorphic rock has been covered by younger sedimentary or volcanic rock
angular unconformity
an unconformity in which younger strata overlie an erosion surface on tilted or folded layered rock
turbidity current
an underwater debris avalanche is also known as a ___
examples of unconformities
angular unconformity disconformity nonconformity
rank the following types of mass wasting from most rapid to slowest
avalanche mudflow earthflow creep
physical continuity
being able to physically follow a rock unit between two places.
formations
bodies of rock considerable thickness with recognizable characteristics that make each distinguishable from adjacent
why wouldnt you use carbon isotopes to date the oldest rocks on earth
carbons half life is too short
the ancestry of the hominids dates back to the beginning of the ___ Era, the age of mammals.
cenozoic
the presence of a nonconformity indicates ___
considerable gap in the rock record erosion to significant depths great amount of uplift
the fastest type of flow is a ___
debris avalanche
correlation
determining time equivalency of rock units. rock units may be correlated within a region, a continent, and even between continents.
which of the following are a result of alpha decay
ejection of 2 protons and 2 neutrons from a nucleus atomic mass number decreases by 4 atomic number decreases by 2
which type of radioactive decay involves the incorporation of an electron into a proton, forming a neutron
electron capture
rank the different divisions of geologic time based upon the length of time covered with the longest at the top
eon era period epoch
most uncomformities represent periods of ____
erosion
mass wasting is commonly classified by the type of movement. A ___ is mass wasting that involves the material moving downslope as a viscous fluid
flow
solifluction
flow of water saturated soil over impermeable material
mudflow
flowing mixture of debris and water usually moving down a channel
index fossil
fossil from a very short lived species known to have existed during a specific period of geologic time
a _ is a scientist who specializes in dating rocks
geochronologist
permafrost
ground that remains permanently frozen for many years
What indicates the presence of a disconformity
if certain fossil beds are absent portion of geologic time is missing presence of a weathering surface at the top of a layer
shear strength
in mass wasting the resistance to movement or deformation of material
earth
in mass wasting, soil in which fine grained particles are predominant
shear force
in mass wasting, the component of gravitational force that is parallel to an inclined surface
determining the age of a rock through its radioactive elements is called
isotopic dating
a disconformity is the hardest unconformity for geologists out in the field to detect because___
it often appears to be just another sedimentary contact (or bedding plane) in a sequence of sedimentary rock
a distinctive layer, known as ___ bed can be used to correlate rocks over great distances
key
volcanic mudflows and debris flows are often called
lahars
which of the following is the general term used for the slow to rapid descent of rock or soil
landslide
mud
loosely used for silt and clay, usually wet
debris flow
mass wasting involving the flow of soil (unconsolidated material) in which coarse material (gravel,boulders) is predominant
rotational slide
movement along a curved surface in which the upper part moves vertically downward while the lower part moves outward also called a slump
mass wasting
movement caused by gravity in which bedrock rock debris or soil moves downslope in bulk
slide
movement of a relatively coherent descending mass along one or more well defined surfaces
difference between mud and earth
mud has high content of water clay and silt
paleozoic cenozoic mesozoic
old life new life middle life
how does a disconformity form?
older rocks eroded away parallel to the horizontal bedding plane; renewed deposition later buried the erosion surface
What evidence can be used to determine that the granite is younger than the tilted layers and older than the horizontal layers
pebbles of granite presence of inclusions cross-cutting relationships contact metamorphism principle of superposition
rank the geologic periods of the paleozoic, with the most recent on the top
permian carboniferous pennsylvanian mississippian devonian silurian ordovician cambrian
geologists look for __ as a way to correlate rock units found in different places
physical continuity
what time interval covers the majority of geologic time
precambrian
superposition
principle or law stating that within a sequence of undisturbed sedimentary rocks, the oldest layers are on the bottom and the youngest on top
lateral continuity
principle that states that an original sedimentary layer extends laterally until it tapers or thins at its edges
match the species with the geologic time interval they are known for precambrian paleozoic mesozoic cenozoic
prokaryotes,algae, soft body trilobites dinos mammals
which of the following are a result of electron capture
proton in the nucleus captures an orbiting electron
the spontaneous nuclear change of isotopes with unstable nuclei is called ____ and can be measured with a gelger counter
radioactive decay
rockslide
rapid sliding of a mass of bedrock along an inclined surface of weakness
rockfall
rock falling freely or bouncing down a cliff
which of the following can be used to correlate rock units between two areas
rock type
the type of mass wasting that occurs when a block of bedrock breaks off a cliff is a ___
rockfall
True about isotopes of a given element
same number of protons different number of neutrons different atomic masses
the order of formation of angular unconformity
sedimentation folding erosion renewed deposition of sediment
earthflow
slow to rapid mass wasting in which fine grained soil moves downslope as a very viscous fluid
what materials are the dominant components of mudflows
soil water sand silt clay
what are true regarding the geologic time scale
standard scale that is used worldwide based on fossil assemblages it was first created using relative relationships
which of the following types of surfaces are susceptible to landslides?
steeper parts of the ocean floors slopes in arid regions where plant cover is sparse steep rocky cliffs along the coast
paleontology
study of fossils
unconformity
surface that represents a break in the geological record, with the rock unit immediately above it being considerably younger than the rock beneath
Contacts
surfaces separating two different rock types or rocks of different ages
___ is the large amount of geologic time that occurred before the Paleozoic
the Precambrian
original horizontality
the deposition of most water-laid sediment in horizontal or near-horizontal layers that are essentially parallel to Earth's surface
translational slide
the descending mass moves along a plane approximately parallel to the slope of the surface
landslides
the general term for a slowly to very rapidly descending mass of rock or debris
actualism
the principle that the same processes and natural laws that operated in the past are those we can actually observe or infer from observations as operating at present. under present usage, uniformitarianism has the same meaning as actualism
which of the following are a result of beta decay
the release of an electron from a nucleus
finding several species of fossils rather than just one, in the same rock layer is more useful for correlation with other rock layers because ___
the sediment must have been deposited at a time when all the species represented existed
relative time
the sequence in which events took place (not measured in time units).
fall
the situation in mass wasting that occurs when material free falls or bounces down a cliff
some fossil species are of little value to geologists for correlation because __
the species thrived during too large a portion of geologic time
half life
the time it takes for a given amount of a radioactive isotope to be reduced by one-half
the half life of an isotope is equal to ___
the time it takes for half the parent isotopes to decay
the boundaries between the three eras of the standard geologic time scale re defined by ___
the two great mass extinctions
relief
the vertical distance between points on Earths surface
it is possible to state with confidence that the rocks at locations A and B are part of the same unit because
they are physically continuous with each other
sudden event that may trigger mass wasting of a hillside is a ____
trigger
debris
unconsolidated material (soil) in which coarse-grained fragments predominate
correlation by similarity of rock types is more reliable if __
unusual sequence of rocks is involved
debris avalanche
very rapid and turbulent mass wasting of debris air and water
rock avalanche
very rapidly moving turbulent mass of broken up bedrock
creep (soil creep)
very slow continuous downslope movement of soil of debris
using the principle of cross cutting relationships, it is possible to determine that the dike is ____ than the granite but ___ than the foster city formation
younger older