Geology Homework

If one half-life has lapsed, what is the radioactive parent to stable daughter isotope ratio?

50:50

The Raplee Monocline is another prominent feature proximal to Comb Ridge in southern Utah, but much smaller in size (approx. 8 miles in length). Note that we are not looking along the flank or axis of this monocline, but instead at an oblique angle. Numerous canyons cut into the structure, thus exposing the interior of the monocline. Choose the correct description regarding the orientation of the beds at A, B, and C in the photo.

A and C beds are horizontal, B beds are tilted

What scenario requires a geologist to use the principle of cross-cutting relationships?

A dike truncates layers in a sedimentary succession

Choose the correct definition of a monocline

A large steplike fold in otherwise flat-lying sedimentary rocks

Which of the following is associated with an erosive surface?

A stream running across an irregular surface

If a rock contains ten different kinds of fossils, which of the following must be true?

All of the organisms had to be alive when the rock was deposited

The San Rafael Swell is a large kidney-bean shaped monocline in central Utah. This feature extends for 75 miles from north to south. The photo below was taken from the east flank of the Swell, looking north. Recall from the video that since monoclines are large-scale features, we can only see a small part from our vantage point. As a review question, which part(s) of the San Rafael Swell do you see in the photo, corresponding to A, B, and/or C on the diagram below?

B and C only

Based on what you learned in the video, which of the following statements regarding joints is true?

Based on what you learned in the video, which of the following statements regarding joints is true?

Imagine two rocks. Under enough stress, rock A will experience plastic strain, whereas rock B will experience brittle strain. Which of the following statements about rocks A and B is true?

Both rock A and rock B will experience elastic strain before plastic or brittle strain sets in.

Following the deposition of a sequence of sedimentary rocks, which event is the first to occur to produce an angular unconformity?

Deformation

A(n) __________ exhibits sedimentary layers that are parallel to each other above and below an erosive surface

Disconformity

What is the orientation of a fold's hinge line with respect to the orientation of plunge?

Hinge line is in the direction of plunge.

The Principles of ___________ and __________ were used to determine relative ages in the previous question

Inclusions, Cross-Cutting Relationships

Which of the following statements regarding radioactive decay is true?

More daughter products accumulate over time

A series of synclines and anticlines is oriented with the hinge lines of the folds trending east-west. From which directions did the force come to create these folds?

North-South

__________ faults combine elements of strike-slip and dip-slip motions

Oblique-slip

In southeast Utah, the San Juan River and its tributaries have cut through hundreds of feet of Paleozoic sedimentary rocks. The photo below shows the Honaker Trail Formation, the Halgaito Formation, and the Cedar Mesa Sandstone. Each unit is composed of rocks that were deposited in distinct environments, and record the transition from a marine to continental setting. The Honaker Trail Formation is made up of predominately carbonates, which record deposition in a shallow marine setting. The Halgaito Formation is located above the Honaker Trail Formation. This unit is composed of siltstones and sandstones deposited in channel and flood plain environments on a coastal plain. The layers of the Cedar Mesa Sandstone make up the steep cliffs of this region. This unit is composed of sandstones, which accumulated mostly in an eolian, or wind-blown environment. Use the information above and your knowledge of relative dating to rank the geologic events from oldest to youngest. Pay particular to the sediments and depositional environments for each formation.

Oldest Event - Youngest Event 1.Carbonate sediments were deposited in a shallow marine depositional environment. 2. Sediment was deposited in stream and floodplain depositional environments. 3. An abundance of sand was transported and deposited by wind in a large dune field. 4. The San Juan River and tributaries incised downward into preexisting sedimentary rock units.

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?

Paleozoic

Which represents the correct sequence from oldest to most recent or current eras on the Geologic Time Scale?

Paleozoic, Mesozoic, Cenozoic

Which eon translates to "visible life" from the Greek?

Phanerozoic

Which of the following is required for a monocline to form?

Reactivation of steeply-dipping faults in basement rocks

Which of the following examples best illustrates the effects of ductile deformation?

Rocks along a convergent plate boundary are subjected to compressive force for millions of years and are permanently folded

Which organism from the video is the least useful for relative dating?

Scallop

Below is an image showing part of the Split Mountain Anticline of Dinosaur National Monument, Utah. It is quite large, so we are looking at only a small portion of the anticline's southern flank. In this photo, you can see sedimentary rocks that have been exposed by weathering and erosion. Yellow lines show curved light-colored sandstone beds that are exposed in canyons cut into the anticline. Orange lines point out red- to orange-colored dipping sedimentary beds that have been eroded from the upper part of the anticline. Concentrate on the series of events that led to the formation and exposure of this anticline. Rank the following events in order from OLDEST to YOUNGEST in age

Sediments are deposited in a horizontal orientation The sediments are buried and lithified into sedimentary rock Compressional forces causes the sedimentarentary rocks to bend into an anticline Process of weathering and erosion exposes the interior of anticline Ranking from oldest to youngest

Which principles of relative dating did you use to answer the previous question?

Superposition and Cross-Cutting Relationships

The San Rafael Swell is a monocline, or large step-like fold, located in central Utah. The photos below were taken on the east and southeast portion of this fold, and show tilted sedimentary beds and canyons from different perspectives. Use the principles of relative dating that were discussed in the video to fill in the blanks of the sentences below.

The "Principle of Cross Cutting Relationships" can be used to determine the relative ages of the sedimentary rocks versus canyon formation. The sedimentary beds were initially deposited in a(n) "horizontal" orientation. The process of stream "incision" is younger compared to the folding of the rock units. The "Principle of Original Horizontality" says that folded sedimentary beds have been disturbed since deposition. The sedimentary layers are "older" than both folding and stream incision.

When viewed from the air, the Bighorn River cuts across the Sheep Mountain anticline. As Sheep Mountain is a topographic high and barrier to streamflow, how was the river able to establish itself and eventually erode through the anticline?

The Ancestral Bighorn River established a course over the landscape while the anticline was still buried at depth

An igneous dike cuts across existing sedimentary layers and erupts at the surface, creating a layer of basalt. The basalt, as well as all the layers below, are then cut by a fault. Which statement is true?

The fault is the youngest because it cuts through all the sedimentary layers and basalt

If a limestone, a shale, and a sandstone are deposited in that order without interruption, which of the following is true?

The limestone is the oldest and the succession is conformable

What is the best definition of fossil range?

The period of time when an organism first and last appears in the sedimentary record

How is the geologic time scale related to the fossil record?

The periods of the time scale were constructed based on ranges of fossil organisms

What happens when stress exceeds a plastic rock's yield strength?

The rock will experience flow

What happens when stress exceeds a brittle rock's yield strength?

The rock will experience fracture

The photo below shows the Comb Ridge monocline of southern Utah, which is approx. 80 miles in length. The view is looking north, along the axis of the monocline. Notice the tilted layers along the axis, and the absence of sedimentary strata to the left (marked by the red bracket). What do you think happened to the sedimentary layers to the left of the axis marked by the red bracket?

The sedimentary layers were worn away by stream erosion

Imagine two rocks. Rock A is weaker than rock B. Which of the following statements about rocks A and B is true?

The yield strength of rock A is lower than that of rock B

How will the orientation of a plunging anticline's limbs change in the direction the fold is plunging?

They will close to a point

Radioactive decay in mineral shows that two half-lives have elapsed, giving an age of approximately 1.4 billion years. Using the table in the video as a reference, what is the correct radioactive parent and stable daughter isotope pair?

U235, Pb207

Which of the following includes all common types of radioactive decay?

alpha particle emission, beta particle emission, electron capture

What kind of force would create the fault in Figure 1?

compression

Which is the shortest interval of geologic time?

epoch

Which of the following is a common feature that all unconformities exhibit?

erosive surface

The anticline that makes up Sheep Mountain is rather small and restricted in extent. What other local feature might be present that would constrain this fold to a small geographic area?

faults in the basement rock beneath the anticline

_____ are shown in the photo above. They are characterized by _____ sedimentary rock layers.

faults, discontinuous

A monocline is a type of a(n) ____

fold

What is the hinge line of a fold?

line of maximum inflection that layers wrap around

What kind of fold is circled in Figure 1?

non plunging syncline

Which fault will see the hanging wall move down relative to the footwall?

normal fault

Which of the following characteristics is the most desirable for constraining the relative age of rocks?

organisms with overlapping ranges and geologically short lifespans

The parking lot of Calico Ghost Town in southern California is a great place to study folds due to excellent exposure and easy access. The series of questions below focuses on types of folds and their components. The photo below shows a fold train, composed of two folds, and their features outlined by orange and red lines. Drag the appropriate labels to their respective targets. Not all labels will be used

p: left -> anticline and right -> syncline down: left -> shared limb right -> axial plane

The photo below shows dipping sedimentary beds exposed along a limb of the Uinta Anticline in northeast Utah. The axial plane of the fold is located to the left of this exposure and not shown in this photo. The red layers in the center of the photo are predominantly sandstones, whereas the lighter-colored rocks that make up the ridge to the right are carbonates. You can see that most of these layers are dipping to the right. The photo below shows dipping sedimentary beds exposed along a limb of the Uinta Anticline in northeast Utah. Imagine you are out in the field and have to sketch and label the view below. Based on observations from the previous photo, which of the following sketches is the most accurate?

pic 5 (number is on the bottom left corner)

Numerous sedimentary beds can be observed driving through the Valley of the Gods in southeast Utah. These sedimentary rocks are in their originally horizontal position, which means they have not been deformed. The spectacular spires and buttes that you see are the result of erosion driven by wind and water. The Principle of Lateral Continuity states that sediments are deposited as continuous beds across a wide area until they transition to another sediment or thin at the edge of a basin. Using this principle, geologists can correlate units across areas where erosion has occurred. Pay close attention to the rock units exposed along these buttes. Using the Principle of Lateral Continuity, can you connect the sedimentary beds in this photo? A photo showing a series of sedimentary rock units that are layered horizontally. Below are a series of sketches that show rock units organized by color, and traced across valleys with dotted lines. The keys include information on rock types and relative ages. Remember creating a clear and accurate key is important when sketching in the field. Pay special attention to the keys in these drawings when you make your choice. Select the correct sketch below.

picture number 4

What kind of fault is visible in Figure 1?

reverse fault

A _____ is formed when magma intrudes between existing sedimentary layers

sill

Which of the following processes resulted in the deformation of sedimentary units in the American West during the Jurassic Period?

subduction of the Farallon plate beneath the North American plate

What is strain?

the amount of deformation that results from an applied force

What is stress?

the force exerted to cause deformation

A cross-section of a monocline is shown below. Use what you learned in the video to label the parts of the monocline and the directional forces that created it.

top left: uplifted sed rock bottom left: half arrow up middle bottom: half arrow down bottom right: crys. basement rocks

A dike, which is a tabular intrusive igneous body that cuts across existing rock structures, is shown below. Notice that this feature cuts through horizontal layers of sandstone, or country rock (outlined in yellow). The inset photograph shows an inclusion, which is a fragment of unmelted crustal rock that was incorporated into a body of magma before it crystallized as a dike. During intrusion, magma caused the crustal rock to fracture and pieces were mixed into the magma. The magma then cooled, preserving the inclusion encased in igneous rock. You can see that the inclusion is different in composition than the surrounding rock. Using principles of relative dating, classify the statements according to whether they are "true," "false,"

true The sandstone country rock is older than the dike.The intrusive igneous rock making up the dike is the youngest in age. False The dike is older than the inclusion.The inclusion formed originally in the sandstone country rock.

The subdivisions of the Geologic Time Scale were based on which criteria or characteristics?

types of fossils within the units

The sedimentary layers above an erosive surface are __________ relative to all rocks present below the surface

younger

Which of the following is an accurate description of a nonconformity?

younger sedimentary strata overlie uplifted and weathered igneous or metamorphic rocks