Oceanography Exams 1-3

The process of seafloor spreading creates what magnetic feature on the seafloor?

Symmetrical stripes of normal and reversed polarity in the oceanic crust on either side of ridges

Samples of Earth’s mantle have never been collected

False

What are good estimates of the average salinity and temperature of the ocean?

34.5g/kg, 3.9C

The depth of the CCD is controlled by *

Temperature and pressure

Above the CCD, CaCO3 … in sediments. Below the CCD, CaCO3 … in sediments.

accumulates, dissolves

In what vertical zone of the ocean would an organism that needs light live?

Epipelagic

A physical oceanographer is knowledgeable about which marine phenomena?

Circulation patterns in the ocean and atmosphere

Calcareous oozes are composed of

Biogenic calcium carbonate

What is the average depth of the ocean

3,682m

What regions have the thickest sediment cover

Abyssal Plains

What can grain shape indicate in a sediment sample?

Transport distance from sediment source

The average depth of the ocean is less than the average elevation of the continents above sea level.

False

What is one region where siliceous oozes dominate the sediments, due to strong upwelling of nutrients?

the Southern Ocean

What geologic processes are responsible for the formation of the following marine features: East Pacific Rise, Mariana Trench, Hawaiian Islands

Plate divergence, plate convergence, mantle plume

Where are shelf breaks found

Between the continental shelf and the continental slope

How would methane gas affect the subbottom profile of an area?

It would wipe out the sediment layers and create voids in the profile

A marine scientist is studying the distribution of nutrients in a shallow coastal sea. They are attempting to connect the data with carbon cycling in the ocean and links to climate. What kind of marine scientist might they be classified as?

Chemical oceanographer

What process created layering in Earth’s structure, from the solid core inside to liquid ocean and atmosphere at the surface?

density stratification

Where would a benthic organism live?

In or on the seafloor

How does the spreading rate affect the topography?

Lower spreading rates lead to more vertical topography

Why are there pelagic clays in the middle of the ocean when the continents are so far away?

The clays are composed of dust transported long distances in winds

How was oxygen first introduced to Earth’s atmosphere?

Oxygen was introduced through the evolution of photosynthetic cyanobacteria

A marine scientist collects water samples over time to analyze how changing climate affects the microscopic community of organisms that inhabit the surface ocean. What kind of marine scientists might they be classified as?

Biological oceanographer

What processes occur at a mid-ocean ridge

Rifting, upwelling of magma, and formation of new crust

What is the best tool for collecting two-dimensional, large-scale bathymerty data?

Multibeam

Earth formed …, the oceans were mostly in place by… and life originated around…

4.6 billion years ago, 4 billion years ago, 3.5 billion years ago

How are submarine canyons formed?

Erosion during periods of low sea level combined with turbidity currents

How do well sorted sediments differ from the poorly sorted sediments

Well- sorted sediments have a narrow range of particle sizes, while poorly sorted sediments have a wide range

The radioisotope 230Th has a half life of 75,400 years. What percent of the original 230Th content would you expect to find in a sediment sample that is about 226,000 years old?

12.5%

How could the growth of a volcanic island on oceanic crust affect the local position of the lithosphere in the asthenosphere relative to surrounding areas with no islands?

The lithosphere supporting the island sinks lower in the asthenosphere

Where is the neritic zone?

Continental shelf

What geological features are commonly associated with convergent plate boundaries?

Trenches

A marine scientist collects bathymetric data to understand the processes that physically created the seafloor and structures on it. What kind of marine scientist might they be classified as?

Marine geologist

The tests or skeletons of diatoms are major components of what sediment type?

Siliceous ooze

Which sequence lists sediment grain sizes from deposition in the highest energy environment to the lowest energy environment.

Sand, silt, clay

Where are authigenic sediment particles formed?

Within the sediment

How do satellites see seamounts?

Detect small changes in sea surface height

On either side of the Mid-Atlantic Ridge, two tectonic plates are moving

Away from each other

What types of boundaries make up the pacific ring of fire?

Convergent boundaries

Describe the steps leading to formation of the oceans shortly after the formation of Earth.

1. Water accumulates on Earth through volcanic degassing and comet/asteroid impacts

2. Water was initially in clouds because the surface was too hot

3. Once the surface was cool enough for liquid water, the water rained out of the atmosphere to form the oceans

Why is there no oceanic crust older than 200 million years old, even though Earth is much older?

There is no oceanic crust older that 200myo because new crust is continuously forming at spreading centers/ridges and this pushed the older crust towards plate boundaries, where most of it subducts and melts in the mantle.

What are some processes that can cause sea level to rise

Melting of land-based ice

How does the density of water change with decreasing temperature from 20c to -5C

Increases first then decreases

Which colors of light entering at the ocean surface are attenuated first and last with increasing depth.

red, blue

When the sun and moon are aligned, a … tide occurs, and when the sun and moon are at right angles to each other relative to Earth, a … tide occurs.

spring, neap

How is residence time defined?

The average time a unit of a substance spend in a given location or condition

Where do tidal bulges form on Earth

On both the side facing the moon and the opposite side facing away from the moon.

How does evaporation from the sea surface affect the salinity of the surface water?

Increases salinity

The thermocline is a pycnocline where the change is density is controlled by a change in temperature.

True

How were most barrier islands formed?

Inundation of shoreline dune/berms during post-glacial sea level rise.

A coastline has headlands marking the edges of small bays, cliffs just behind the water line, and multiple sea arches and stacks. What kind of coastline is this?

Erosional

Brine rejection is caused by what process

The formation of sea ice

In which direction are moving, frictionless objects deflected in the Northern Hemisphere due to the Coriolis effect?

To the right

Why does westward intensification of gyres occur?

The Coriolis force strengthens with distance from the equator

Why did many modern estuaries form after the most recent glacial period

Sea level rose with melting ice

Which of these statements is FLASE about tidal power?

Tidal power can produce almost 50% of the world’s power

What climatic phenomenon is triggered by a weakening in the trade winds over the Pacific?

El Nino

At what depth would a wave with a wavelength of 60 meters begin to interact with the seafloor

30 meters

The movement of sand along a beach is called

Longshore drift

In what general direction would a sea breeze blow at night?

From land to ocean

Which of the following would you expect to have the most energy?

The southern ocean

What property of water allows the evaporation of water to cool down surfaces

Latent heat of vaporization

A current flows south along the eastern coast of South Africa in the Northern Hemisphere. What do you expect to happened between the current and the coast?

Downwelling and low productivity

What role can internal waves play in the surface ocean ecosystem?

They can mix up nutrients from depth to fertilize phytoplankton growth

Water is a … molecule, and … are the bonds that hold multiple water molecules together

polar, hydrogen bonds

A polar molecule is one that

Has a partial positive and negative charges on each end

What is the theoretical net angle of Ekman transport from the wind direction?

90

What is the celerity (speed) of a deep-water wave with a wavelength of 350 meters and a period of 10 seconds?

35m/s

What would happen to the Coriolis effect if Earth’s rotation slowed?

It would weaken

In which ocean ridges does deep water mostly form according to thermohaline circulation

North Atlantic and Southern Ocean

How is sea level along the Louisiana coast rising at 9mm/yr when global sea level rise is only 3 mm/yr

Louisiana is subsiding at 6mm/yr

How do rip currents form?

Water piled up nearshore by breaking waves returns seaward through narrow channels

A wave is created by a steady wind that is still blowing. The wave has a wavelength of 3 m, and is in 6m deep water. What type of wave is it?

forced wave, deep-water wave, wind wave

What distinguishes weather from climate?

Weather is the immediate state of the atmosphere, while climate is the long term statistical sum of weather conditions

How do eastern boundary currents compare to western boundary currents?

Eastern boundary currents tend to be broad, slow, cold, and nutrient-rich

Which of the following is the best example of a free wave?

A tsunami caused by seismic activity

In this picture of a jetty on a beach, which direction is the longshore transport going?

From the bottom of the picture to the top

Downwelling occurs along the equator due to Coriolis deflection of surface water towards the equator creating convergence

False

Which type of ocean current is the Gulf Stream considered to be?

A western boundary current

The trade winds blow… and the westerlies blow…

Towards the west between the equator and 30N/S; towards the east between 30 and 60 N/S

When a parcel of air rises in the atmosphere, it…

expands, cools, and any water vapor in it condenses to rain

Tsunamis can be created by…

Earthquakes, landslides, asteroid strikes

As salinity increases (temperature constant), seawater density…

increases

After a major offshore storm, which waves reach the shore first

Long wavelength wave

What drives thermohaline circulation in the ocean?

Gravity and density differences between water masses

Reduction is defined as the

gain of electrons

In what kind of water are gases more soluble?

Cold water

What is the average pH of the ocean?

8

If more nitrate is added to an iron limited region of the surface ocean, how would you expect the primary productivity to change

no change in the growth of primary producers

If the total amount of fixed nitrogen in the ocean is estimated at 720,300 Tg and fixed nitrogen is added to the system at a rate of 290Tg per year, what is the residence time of fixed nitrogen in the ocean?

2,483 years

An acid is a solution that:

releases a hydrogen ion into solution

In what environment does denitrification occur?

anaerobic

What happens when more carbon dioxide is added to seawater

the pH and the carbonate concentration both decrease

What is the average mixing time for the whole ocean?

1,600 years

Which reservoir of carbon will be the most active, with the shortest residence time?

Atmosphere

The solubility pump for carbon in the ocean is primarily controlled by

temperature of the surface ocean

What type of substance can be formed when two elements with a large electronegativity difference bond?

salt