10-12
A container holds 100 atoms of an isotope. This isotope has a half-life of 1.5 months. How many total atoms will be in the container after 3 months?
100 atoms
After four half-lives of decay, what is the ratio of radioactive parent isotope to stable daughter isotope?
1:15
A container holds 100 atoms of an isotope. This isotope has a half-life of 1.5 months. How many atoms of the radioactive isotope will be in the container after 3 months?
25 atoms
When did the supercontinent Pangaea form?
250 million years ago
Which set of coordinates refers to the toe of the landslide labeled "Qls"?
39°40'49.0" N, 105°12'27.5" W
What is the age of the oldest rock found on Earth?
4 billion years old
A rock sample contains 75 atoms of a parent isotope and 25 atoms of a daughter isotope. The half-life of the parent isotope is 100 years. How old is this rock?
50 years old
When did dinosaurs go extinct?
65 million years ago, at the Cretaceous-Paleogene boundary
What characteristic most directly DISTINGUISHES an angular unconformity from a nonconformity?
Angular unconformities separate rock layers along nonparallel surfaces.
Which mountain range, formed via continental convergence, developed just before the Appalachians of North America?
Caledonian Mountains
Which mountainous range is not the result of continental collision?
Cascades
What era marks the final formation of the Rocky Mountains?
Cenozoic era
Geologists often look at various characteristics of terrane to determine whether it is accreted or not. Terranes formed in different places will have different geologic histories and mineralogies, animal and plant life, and magnetic signatures. After accretion, which tools could a geologist use to differentiate between a terrane and the continent onto which it accreted?
Check if the rocks are made of oceanic lithosphere instead of continental lithosphere. Look for fossils that are distinct from those of the continent. Look at the rock types, and determine if they are distinctly different from the continent.
How is Earth unique from other planets? Check all that apply.
Earth's atmosphere supports varied forms of life. Earth's distance from the Sun produces surface temperatures that support varied forms of life. Earth's core creates a magnetic field that is just strong enough to protect the surface from the solar wind.
The Ural Mountains were formed by the collision of which continents?
Europe and Asia
Five layers of rock are cut by two faults. Both faults cut through all five layers of rock. Fault A breaks through to the surface, whereas fault B does not. Which of the following statements about faults A and B is most accurate?
Fault A is younger than fault B, and both are younger than the five layers of rock.
Using the map of present-day oceanic plateaus and other submerged crustal fragments, determine which feature is most likely to be accreted onto a continent.
Galapagos Rise
What is the principle of cross-cutting relationships?
Geologic features that cut through rocks must form after the rocks that they cut through.
Applying the principle of original horizontality indicates that layers were repositioned from a flat-lying orientation.
Magma intrudes into layers of sedimentary rock and displaces them. We can deduce that the intruded magma that crystallizes is younger than the surrounding sedimentary layers by applying the principle of crosscutting relationships.
Imagine a fold has been eroded to a flat surface. In general, how would you know whether this fold is plunging?
Nonplunging folds look like straight lines at the surface, and plunging folds look like wavy lines.
Which represents the correct sequence from oldest to most recent or current eras on the Geologic Time Scale?
Paleozoic, Mesozoic, Cenozoic
What happens during radioactive decay?
Parent isotopes turn into daughter isotopes.
Which eon translates to "visible life" from the Greek?
Phanerozoic
About 2.2 billion years ago, a significant amount of oxygen appeared in the atmosphere. How does this relate to life on Earth during this time and after? Select the two that apply.
Photosynthesis became an effective way to convert energy from the sun, and oxygen was a significant by-product. Significant amounts of oxygen in the atmosphere contributed to the formation of ozone. This protected life from ultraviolet radiation.
What is the relationship between planetesimals and protoplanets? Check all that apply.
Planetesimals are smaller than protoplanets. Planetesimals combine to form protoplanets.
Which of the following statements about relative and absolute age dating is most accurate?
Relative age dating places rocks and events in chronological order but does not provide information about absolute age.
Imagine a syncline has been eroded to a flat surface. How would the rock age change as you walked across that flat surface?
Rocks would be oldest on the edges and youngest in the middle.
Imagine an anticline has been eroded to a flat surface. How would the rock age change as you walked across that flat surface?
Rocks would be youngest on the edges and oldest in the middle.
What is the principle of original horizontality?
Sedimentary rocks are close to horizontal when deposited.
Which tectonic process has formed the mountain belts along the coasts of Alaska and British Columbia?
Small crustal fragments have been accreted on the northwestern margin of the North American Plate.
Imagine that you could remove the Quaternary deposits to reveal the rocks beneath them. Which answer most correctly describes the outcrop pattern of these rocks?
The Permian through Cretaceous rocks outcrop in parallel bands that run roughly north to south on the left-hand side of the map.
Which argument offers the best evidence that the Quaternary deposits are indeed younger than the Permian through Jurassic rocks in the area?
The Quaternary deposits seem to be draped over the older rocks. One can imagine that the outcrop pattern of the older rocks would be continuous under the Quaternary deposits.
A radioactive element undergoes decay via the loss of two alpha particles to form a stable daughter isotope. Following the decay, what would the atomic number of this newly created stable isotope be?
The atomic number of the daughter isotope would be four units less than the original parent isotope.
How did the Cretaceous-Paleogene extinction influence evolution?
The demise of the dinosaurs led to diversification of mammals
In a normal dip-slip fault, which of the following statements describes the movement of the hanging wall relative to the footwall?
The hanging wall moves down relative to the footwall.
A fault (F) breaks three layers of sedimentary rock (S). An igneous intrusion (I1) has broken through the bottommost layer of rock. A second igneous intrusion (I2) has moved up the fault and pooled on top of the uppermost layer of rock. Which event would be considered the youngest?
The intrusion of I1 or I2 is the youngest event. Without more information, we cannot know which igneous rock is youngest.
As an island arc system collides with the edge of a continental landmass, which tectonic scenario would be the result?
The island arc is peeled off the oceanic plate and a volcanic arc is produced by subduction.
Where do the oldest rocks in this area outcrop, and how old are they?
The oldest rocks in this area outcrop on the western side of the map and are Precambrian in age.
Two containers hold the same radioactive isotope. Container A contains 1000 atoms, and container B contains 500 atoms. Which of the following statements about containers A and B is true?
The rate of decay of atoms in container A is greater than the rate of decay of atoms in container B.
In the field you encounter a sequence of sedimentary rocks that has a dike running through them. A normal fault crosses the entire sequence, cutting off part of the dike near the surface. Which scenario best describes your observations? (All scenarios list events from oldest to youngest.)
The relative ages of the sequence are as follows: sedimentary rocks > dike > normal fault.
After the occurrence of a normal dip-slip fault in flat-lying sedimentary rocks, the fault scarp produced is eliminated by erosion. What is the age of the rocks on the surface of the footwall side of the fault relative to those on the hanging wall?
The rocks on the footwall side of the fault would be older than those on the hanging wall side.
When a terrane impacts the margin of a continental plate, what is the fate of the oceanic plate upon which the terrane has been traveling?
The terrane cannot be subducted, which causes the oceanic plate on which it has been traveling to break off and continue downward beneath the continental crust.
Of the following statements, which accurately describes the Anthropocene epoch?
There is much debate among scientists as to when the Anthropocene epoch began. The term Anthropocene conveys that we are now living in a time period that is strongly shaped by human activities, resulting in environmental change. During the Anthropocene, human activity has caused some plant and animal species to become extinct.
What is a possible age of the Ralston Creek Formation? All of the units in Image 1 are in a stratigraphic order, but keep in mind that these rocks have been deformed following their deposition. Determine which way is "up" in the stratigraphy and assign an age to the Ralston Creek Formation.
Triassic
What is the principle of superposition?
Within a sequence of rock layers formed at Earth's surface, rock layers lower in the sequence are older.
What produces plunging folds?
a combination of folding and tilting
What is a syncline?
a fold shaped like a right-side-up U
What is an anticline?
a fold shaped like an upside-down U
What does the term plunging fold mean?
a fold that is tilted down into Earth
What was the "Cambrian Explosion"?
a sudden large increase in life forms, during which all major groups of invertebrates came into being
Which feature is not considered a rock structure?
aa
What hypotheses have been proposed to explain the demise of the dinosaurs? Check all that apply.
asteroid impact huge volcanic eruptions
How long ago did life first appear on Earth?
at least 3.5 billion years ago
During deformation of sedimentary rocks, which type of stress produces folds?
compressional
Which type of force causes folding?
compressional force
Which type of stress on rock is uniform in all directions?
confining pressure
In which tectonic setting would you expect to observe overthrust faults?
convergent boundaries
How is the atomic number of an atom determined?
counting the number of protons in the nucleus
Which of the following rocks appears to be the most resistant to weathering and erosion?
crystalline basement
Which list best describes the events that would lead to the layering of sedimentary rocks in this diagram?
deposition, erosion, deposition, erosion, deposition
Which type of stress produces most crustal deformation?
differential stress
Folded rocks are uncommon in which tectonic setting?
divergent boundaries
The Black Hills of South Dakota are a good example of which feature?
dome
Folds exhibit which type of deformation?
ductile
Which is an example of radioactivity that occurs when a neutron is converted to a proton and an electron is emitted from the nucleus?
emission of a beta particle
Which is the shortest interval of geologic time?
epoch
compressional
folded rocks reverse fault dip angle >45 degrees thrust fault dip angle <45 degrees
What type of tectonic activity led to the formation and uplift of the Andes on the western margin of the South American Plate?
formation of a volcanic arc
during the anthropocence
in the last decade, the black rhinoceros of west africa became extinct drainage patterns across the globe are altered due to dams and road building atmospheric CO2 has increased more quickly, and to higher concentrations, than during any other part geologic time
What term describes an erosional surface bounded above by flat-lying sedimentary rocks and below by igneous or metamorphic rocks?
nonconformity
In the following rock sequence, how much erosion might have occurred between rock layer A and rock layer B?
none or only a very small amount (Time does not equate to erosion.)
tensional
norma fault
Which type of fault is found in the Great Rift Valley of East Africa?
normal
Which process is not a common form of natural radioactive decay?
nuclear fission
The fact that sedimentary rocks are almost always deposited in a horizontal position reflects which law or principle of geology?
original horizontality
Which term is used to describe a fold in which one limb has been tilted far beyond the vertical?
overturned
Which material, principle, or process enables a method of numerical dating?
radioactivity
Which feature would you expect to find associated with continental collisions?
reverse faults
What colors are used to represent rocks from the Permian through Jurassic periods?
shades of blue
Generally, in what colors are the Quaternary deposits drawn?
shades of yellow, orange, and brown
Which type of stress would you expect to find at a transform boundary?
shear
Which principle or law of geology states that in a sequence of undeformed sedimentary rocks, each bed is older than the one above?
superposition
Which type of stress would you expect to find at a divergent boundary?
tension
Which type of stress has produced the fault-block mountains in the Basin and Range Province?
tensional
What do geologists call small accreted crustal fragments that have a geologic history distinct from adjacent blocks?
terranes
Which is not an example of a small crustal fragment that could collide with a continental landmass, forming mountainous topography?
the British Isles
While working in the field, you find some sedimentary rocks that include hundreds of fossils of crinoids, numerous brachiopods, and a few trilobites. Realizing that these ancient organisms are some of the first with hard parts, and (when taken as a group) are not very similar to animal communities living today, in which unit of geologic time would you place these rocks?
the Paleozoic
What is the scientific definition of half-life?
the amount of time over which the number of parent isotopes decreases by half
before the anthropocene
the first oxygen-producing bacteria evolved, creating the oldest fossils on earths. 66million years ago, a massive asteroid struck earth, resulting in the extinction of 3/4 of all plants and animal life, including dinosaurs.
Which principle of relative age dating is important for determining the relative age of igneous rock that has intruded into overlying rock?
the principle of cross-cutting relationships
While working in the field, you encounter an outcrop in which sandstone, shale, and limestone have been intruded by a basaltic dike. You know that the basaltic dike is younger than the sedimentary rock by applying which law or principle?
the principle of cross-cutting relationships
The subdivisions of the Geologic Time Scale were based on which criteria or characteristics?
types of fossils within the units
Which event is generally used to indicate the beginning of the Phanerozoic eon?
widespread occurrence of hard parts