Geology 101 - Assignment 3

This image shows folded layers of sandstone and shale in an outcrop of the Stellarton Formation (Pennsylvanian) near New Glasgow, Nova Scotia. None of the layers is overturned. Which of the following portions of the diagram corresponds to Unit 4?

Although the orientation of the bed changes, Unit 4 remains under Unit 5 when it emerges from the subsurface. The thick dark bed labeled "D" corresponds to Unit 5, with Unit 4 beneath it labeled "C."

Which statements are true of anticlines?

Anticlines are the result of ductile deformation in response to compressional stress. They have an arch-like shape in which the limbs dip away from the hinge.

A number of geologic principles allow geologists to observe the relative ages of rocks. Which of these images illustrates the principle of inclusions?

B+C

Although depositional environments (and the resulting rock types) can change over broad areas, fossils within the rocks allow geologists to correlate units despite any lithological differences. Below is an image of fossils found in an outcrop. A limestone in another outcrop 150 miles away contains fossils C and E. Which bed (labeled 1 through 10 on the image) does this limestone correlate to?

Bed 6 is the only one that contains both fossils C and E.

Label the diagram depicting the characteristics of a collisional orogen

During collision, two continents suture together. In the interior of the mountain belt, metamorphic rocks are brought up from depth. On the margins of the mountain belt, fold and thrust belts develop.

Select statements true of ductile deformation in solids. Note that ductile deformation is also called plastic deformation.

During ductile deformation, rocks can bend or fold. This usually takes place at great depths and high temperatures.

Label the diagram below describing the orientation of geologic structures.

Geologists use this information to draw accurate geologic maps and cross sections.

The labeled areas in the center of the North American craton represent smaller crustal blocks that were sutured together during the

Large continental landmasses formed for the first time during the Proterozoic. The assembly of the North American craton culminated with the Grenville Orogeny roughly one billion years ago.

The diagram below shows a cross section through the Appalachian Mountains. This deformation is associated with which of the following events?

Much of the deformation in the Appalachian Mountains formed in the Pennsylvanian during the Alleghanian orogeny.

Which statements are true about normal faults?

Normal faults are the result of tensional stress and result in lengthening of the crust. In normal faulting, the hanging wall moves down relative to the footwall; this type of motion is known as dip-slip motion.

Sideling Hill, in western Maryland, is a northeast-southwest-trending ridge underlain by Paleozoic sandstone, shale, and coal. This fold formed due to the collision of Africa with North America. Note that the compass shown over on the highway points approximately north. Drag each of the labels so it overlies the appropriate target. The trace of a marker horizon is shown in purple. Remember that "dip" refers to the angle that a layer makes relative to the horizontal.

Note that one limb is sloping (dipping) in the same direction that the truck is traveling. The limb in the distance is sloping (dipping) in the direction that the truck came from. The hinge zone is the transition between the two limbs.

These beds of sandstone and shale (now metamorphosed to quartzite and slate) are part of the Meguma Group (Cambrian-Ordovician) in eastern Canada. Which of the following best characterizes the type of folding seen in these beds?

Notice that the beds show thickening in the hinge and thinning in the limbs—the hallmark of passive-flow folding.

Be able to order the rock layers chronologically. Easy level, moderate,

Oldest to youngest, bottom to top

Watch the Introduction to the Faults Animation found here, and label the following fault components on the diagram.

Remember the fault scarp in a normal fault exposes the fault plane. In a reverse fault, the fault plane is often obscured as the scarp collapses.

Which statements are true about reverse faults?

Reverse faults are the result of compressional stress and result in shortening of the crust. In reverse faulting, the hanging wall moves up relative to the footwall; this type of motion is known as dip-slip motion.

Be able to order the steps of the formation of a nonconformity.

Sedimentary rock layers are deposited and then intruded by a pluton. Erosion exposes the pluton at the surface. Sediments are once again deposited, covering the erosional surface.

Be able to order the steps of the formation of an angular unconformity.

Sedimentary rocks are emplaced and then folded. Erosion takes place, followed by more deposition.

Be able to order the steps of the formation of a disconformity.

Sediments are deposited in a Marine environment. When sea level falls, exposing the marine sediments, erosion takes place. When sea level rises again, the erosional surface is buried by more marine sediments, creating a disconformity.

Which statements are true about synclines?

Synclines are the result of ductile deformation in response to compressional stress. They have a trough-like shape in which the limbs dip toward the hinge.

Sort these mountain chains based on what caused them to form.

The Alps, Himalayas, and Appalachian Mountains all formed via continental collision.

The folding and faulting in these mountains is approximately what age? This cross section shows a fold-thrust belt. In this belt, thrust faults merge with a subhorizontal detachment. Is this belt in the northwest half or the southeast half of the cross section?

The Appalachians were formed during the Carboniferous and Permian Periods of the Paleozoic Era. The fold-thrust belt consists of the tan-colored units that are cut by faults and are deformed into folds.

Which of the following is the youngest bed in the image?

The bed labeled "E" represents Unit 6, which was deposited atop Unit 5 and is the youngest interval exposed in this outcrop. The beds to the left of Unit 6 come up from depth and crop out at the surface again.

Label the illustration of a fault.

The hanging wall was named by miners because it hung over their heads; the footwall lay beneath their feet. The fault trace is the intersection between the fault plane and the ground surface. Vertical motion on the fault surface can create a step-like surface in the landscape called a fault scarp.

Match each type of strain taking place to the corresponding image of a cube and fossil shell. Red arrows indicate the stress acting on the cube and shell. The terms provided refer to changes in the horizontal direction.

The original shape of the fossil is the unstrained shape. Shear transforms angular relationships, shortening makes the features narrower, and stretching makes them longer.

This image shows strata exposed in the walls of the Grand Canyon. Identify the oldest and youngest rocks by dragging the labels to the appropriate location. Which of the following is most useful for justifying your age assessment?

The principle of superposition tells us that the oldest rocks are at the bottom of the sequence and the youngest are at the top.

The accompanying diagram shows deposits formed by the rise and fall of sea level in a gently subsiding sedimentary basin. Which of the following statements accurately describe the events recorded by these rocks?

The unconformity formed because the land surface was exposed and eroded. The black shale was deposited in the deepest water. Sea level was highest when the shale was deposited.

Select the statement that best describes the concept of fossil succession.

There is a definite relative order in which each fossil species occurs within the layers of rock on Earth.

Which major climatic and biologic events happened during the Pleistocene Epoch?

There were numerous extinctions of large animals toward the end of a glaciation. Much of the northern hemisphere experienced an ice age.

Sideling Hill, in western Maryland, is a northeast-southwest-trending ridge underlain by Paleozoic sandstone, shale, and coal. This fold formed due to the collision of Africa with North America. Note that the compass shown over the highway points approximately north. What kind of fold is this?

This fold is shaped like a trough, with the limbs dipping toward the hinge, making this a syncline.

Which statements are true about William Smith's discoveries?

Using fossils, the relative order in which different rock layers were deposited is discernable. Not all fossil species are present in all locations. The relative vertical order of fossils is the same in all outcrops.

This image shows the way that North America might have looked 90 million years ago, during the Late Cretaceous. Label the diagram with the tectonic features listed.

What happened to the convergent boundary during the Cenozoic?

Identify North America's geologic provinces by dragging the labels to the indicated regions.

Which region overlies Cretaceous and Cenozoic strata?

Unconformities develop when new sedimentary layers accumulate atop old, eroded layers, resulting in a geologic hiatus.

be able to identify all kinds of disconformities

When a meteor exploded above Chelyabinsk, Russia, on February 15, 2013, the resulting shockwave broke windows and damaged buildings across the region. Which of the following was the result of an earlier, much larger meteorite impact?

extinction of dinosaurs and many other life forms 65 million years ago

Geologists use epochs to further divide geologic eras and periods. Put the following epochs from the Cenozoic Era in chronological order, from the earliest to the most recent.

pliocene - miocene - oligocene - eocene - paleocene

How do you recognize faults in the field?

powdered rock, offset of layers on opposite sides of the fault, development of drag folds along the fault interface, shattered rock, slickensides