ERSC 1302 - Oceanic floors

On average, how many damaging earthquakes occur each year?

1000

Imagine you are swimming in the open ocean at a location near the equator. Based on the following data, can you determine how deep you would need to dive to reach a water temperature of 19°C? Seawater temperature at the surface: 24°C Thermocline: 1°C per 50 meters of depth (occurs between 300 and 1000 meters) a) 5 meters b) 550 meters c) 250 meters d) 190 meters

550 meters (You would need to dive 550 meters to reach a water temperature of 19°C.)

Which feature would you expect to find at the mouth of a submarine canyon? a) talus slope b) delta c) a deep sea fan d) beach e) alluvial fan

A deep sea fan (Deep sea fans form when the velocity of a turbidity current moving downslope through a submarine canyon decreases, depositing sand and mud at the mouth.)

Imagine a researcher aboard an oceanographic vessel collects samples from the water column, extending from the surface to 3000 meters depth. Sample analyses shows that the water is isopycnal. Which of the following statements correctly define what this means and why? Select the three statements below that apply. A) The sample analyses show there is no pycnocline present. B) Isopycnal means the samples of the water column have constant temperature throughout its depth. C) The samples must have been taken from a location in the ocean at high latitude. D) The temperature of the water column is constant throughout its depth.

A) The sample analyses show there is no pycnocline present. C) The samples must have been taken from a location in the ocean at high latitude. D) The temperature of the water column is constant throughout its depth. (The sample is isophycnal, meaning that the temperature of the water column must be constant throughout its depth, the sample must have been taken from a location in the ocean at high latitude, and the sample analysis shows no pycnoline present).

What is a seamount? a) An inactive volcano that occurs along the trench of subduction zone. b) An inactive volcano that occurs along the crest of the mid-ocean ridge. c) An active volcano that occurs along the trench of a subduction zone. d) An active volcano that occurs along the crest of the mid-ocean ridge.

An active volcano that occurs along the crest of the mid-ocean ridge.

During deformation of sedimentary rocks, which type of stress produces folds?

Compressional

Which type of force is responsible for reverse fault formation?

Compressional force

Which type of stress on rock is uniform in all directions?

Confining pressure

Which is not one of the three broad zones describing the ocean floor? a) Continental margin b) Deep-ocean basin c) mid-oceanic ridge d) continental slope

Continental Slope (The continental slope is included within the continental margin zone of the ocean floor)

Moving off the east coast of North America, identify the sequence of environments you would encounter as you move deeper into the Atlantic Ocean. a) continental slope, continental shelf, continental rise, abyssal plain b) continental shelf, continental slope, continental rise, abyssal plain c) continental margin, mid-oceanic ridge, deep-ocean basin, abyssal plain d) continental margin, continental slope, continental rise, abyssal plain e) continental shelf, continental slope, mid-oceanic ridge, abyssal plain

Continental shelf continental slope continental rise abyssal plain (As you move off the east coast of North America you would encounter the continental shelf (a flooded extension of the continent), the steep continental slope, the gently sloping continental rise, and finally the flat abyssal plain.)

Which is not one of the three broad zones describing the ocean floor?

Continental slope

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

Most earthquakes are the result of movement along which of the following features?

Faults

The point within Earth from which earthquake wave energy radiates is known by which of the following terms?

Focus

What is a fault?

Fractures along which ricks move

Which of the following events allows rocks on either side of a fault to rebound elastically, causing an earthquake?

Friction along the fault plane is overcome

When considering mass wasting, which of the following factors is most influential in the downslope movement of weathered particles?

Gravity

Which feature is considered a rock structure?

Joint, fault, fold, fracture

During the eruption of Mount St. Helens on May 18, 1980, snow and glacial ice on the mountain melted and rushed down the Toutle River. What is the name given to this specific type of mass wasting?

Lahar

Which response best explains the absence of volcanoes and earthquakes at a passive continental margin?

No earthquakes or volcanoes can occur due to the distance from any active boundaries . (Passive continental margins develop on the trailing edge of a continent, where deposition of continental sediment is the dominant process. The significant distance from any tectonic activity leads to a lack of earthquakes and volcanoes.)

Which term is used to describe a fold in which one limb has been tilted far beyond the vertical?

Overturned

Of the following types of mass wasting, which tends to be the fastest moving and most destructive?

Rockslides

Which type of stress would you expect to find at a transform boundary?

Shear

Which type of force is responsible for normal strike-slip formation?

Shear force

During the 1906 San Francisco earthquake, the Pacific Plate moved 4.7 meters (15 feet) north relative to the North American Plate. Which of the following types of stress was exerted on the rocks during this earthquake?

Sheer stress

At a local landfill, the liner beneath the trash was being repaired. In the process, trash from the base of the slope was removed and piled on top of the landfill. After an unusually heavy rainfall, the slope failed very quickly along a curved surface. Which of the following types of mass wasting best describes this slope failure?

Slump

Which of the following examples of mass wasting is characterized by a crescent-shaped scarp or cliff at its head?

Slump

Which type of stress would you expect to find at a divergent boundary?

Tension

Which type of force is responsible for normal fault formation?

Tensional force

What are rocks below and above a fault called?

The footwall below and the hanging wall above

When dry sediment accumulates, the angle of repose represents what property of the deposit?

The steepest angle at which those sediments can accumulate and remain stable.

Which coast represents an active continental margin? a) the west cost of Europe b) the east coast of North America c) the west coast of Africa d) the east coast of Africa e) the west coast of South America

The west coast of South America (Due to the subduction of the Nazca Plate beneath the west coast of South America and the resultant growth of the Andes, this region is considered an active continental margin.)

Which statement best explains the formation of seamounts?

They represent volcanoes situated over mantle plumes that have since moved away from their source of magma and subsided. (Similar to the formation of the Hawaiian Islands-Emperor Seamount chain, many other seamounts represent volcanoes that have moved off a magma source and have been eroded below sea level.

Which of the following responses are examples of how water can promote mass wasting?

Waves and streams can undercut banks and cliffs, causing them to fail. Water can saturate sediment, reducing the integrity of the slope and allowing it to move. When water is added to weathered particles, the mass of the sediment is increased, which can cause slope instability.

What is a tablemount? a) A seamount that grew to just below sea level, experienced wave erosion, and is now inactive. b) A seamount that grew above sea level, experienced wave erosion, and is now inactive. c) A seamount that grew above sea level, experienced wave erosion, and is now active. d) A seamount that grew to just below sea level, experienced wave erosion, and is now active.

a seamount that grew above sea level, experienced wave erosion, and is now inactive.

Both the thermocline and pycnocline present a _______ to mixing between near surface waters and deep ocean depths.

barrier

Water ________________ when it is heated, making the density _______________.

expands, decrease

In lower latitudes where a thermocline exists, as we drop down from the surface through ocean water, water density will ________________ while water temperature will respond inversely.

increase

We expect a water column to be ____________ for density at high latitudes.

isopycnal

Water that is _________________ will be rpresented by a straight line on a graph showing variations in temperature with depth.

isothermal

The Sun penetrates surface waters enough at _________________ to create a thermocline.

low latitudes

The steepest angle at which those sediments can accumulate and remain stable.

slight addition of water to the sediment

Which of the following types of mass wasting is extremely slow and occurs when saturated soil flows downslope?

solifiluction