Oceanography

Where is the oldest oceanic crust? Why?

Near subduction zones, the oldest is in the western Pacific near Japan. It is the farthest distance from a spreading center

What are the characteristics of a divergent boundary? Give an example.

New crust is formed as the plates move apart, a ridge forms and there are many small volcanoes. The mid- atlantic ridge

At what type of plate boundary are tranches and island arcs found?

Ocean-ocean convergence

List the three types of waves generated by an earthquake in order of their speed of travel from fastest to slowest

P waves, S waves, surface waves

What is the biggest Ocean? What is the smallest?

Pacific Ocean, Indian Ocean

What are sediments?

Particles of organic or inorganic matter that accumulated in a loose form

What are the four major disciplines of oceanography?

Physical, Chemical, Geological, and Biological

What are terrigenous sediments and how are they transported to the ocean?

Terrigenous sediments come from erosion of rocks and soil on land. They are transported to the ocean primarily by rivers, but also by wind

What are the four major sources of sediments?

Terrigenous, biogenous, hydrogenous, cosmogenous

Why is the 'Big Bang' important, what did it do? When did it occur?

The 'Big Bang' catalyzed the formation of the universe. It occurred 13.7 billion years ago

What is paleomagnetism? How do we use that information?

The 'fossil' magnetic field frozen in cooled magma that shows the polarity of the Earth at the time the rock was formed by examining the direction the magnetite is aligned. We use it to calculate the rate of spreading at divergent boundaries.

Why are pelagic sediments thicker in the Atlantic than Pacific?

The Atlantic has more rivers inputting sediment, it is smaller, and has fewer subduction zones.

What is different about how the islands of Japan and Hawaii were formed? Be specific about what is happening with the plates.

The Japanese islands are formed at an ocean-ocean convergence where one plate is subducted and the melting of the subducted plate causes volcanic activity that forms an island arc. In the case of Hawaii, a plate is moving over a hotspot or mantle plume and a volcano and island are formed over the hotspot, and then carried away as the plate continues to move.

What is the deepest trench we know of and how deep is it?

The Mariana trench. It is 11,000m deep (11km)

What is different about the bathymetry of the Mid Atlantic Ridge versus the East Pacific Rise? Why?

The Mid Atlantic ridge has more pronounce mountains and valleys in it's bathymetry. It has a slower spreading rate and so it's features are more compact around the spreading center

Why does the continental shelf in the Gulf of Mexico have numerous pit or pockmarks

The Mississippi river and other rivers have deposited large amounts of sediments on the shelf. The weight of the sediments causes salt domes to rise and spread out, they dissolve and collapse causing the pits.

What is buoyancy?

The ability of an object to float in a fluid by displacing a volume of that fluid that is equal to the object's weight

What is the shelf break?

The abrupt transitions from the continental shelf to continental slope

What are the characteristics of a passive margin? Give an example.

There is little earthquake activity. Faces a divergent plate boundary. Has a broad continental shelf. The Atlantic Ocean

What was the significant finding of the Fram expedition?

There was no landmass in the Arctic

How are submarine canyons aligned with the continental shelf and how are they formed?

They are aligned at right angles with the shelf and they are farmed by turbidity currents

What happens to waves from an earthquake as they pass through a planet with a density gradient?

They are bent

What are biogenies sediments? Where are they most abundant?

They are biological in origin, mostly from plankton. They ardmore abundant in areas of high productive like continental margins and upwelling areas.

What are the characteristics of poorly- sorted sediments? Under what flow conditions are they found?

They are composed of particles of a range of sizes. They are found where energy fluctuations occur over a wide range. (wide range of current speeds)

What are the characteristics of well sorted sediments and under what flow conditions are they found?

They are composed of particles of primarily all the same size. They occur where energy fluctuations happen in a narrow range (narrow range of current speeds)

What are the characteristics of the bathymetry of the abyssal plains and why?

They are generally smooth and featureless due to the accumulation of sediments

What are hydrogenous sediments? Where might they found?

They are sediments formed from minerals precipitating from seawater. They are found at hydrothermal vents and areas where new crust is forming as well as areas where these substance may have been transported to the ocean by rivers

Where are pelagic sediments thickest? Thinnest?

They are thickest over the abyssal plain and thinnest over the ridge systems

What is important about the pockmarks and pits of the Gulf of Mexico's continental shelf

They cause oil and gas to rise towards the surface and be more accessible

What are Neritic sediments? What are their characteristics?

They overlay the continental margins. They are composed of mostly terrigenous sediments and biogenies sediments in areas of high productivity

What are pelagic sediments? What are their characteristics?

They overlay the continental slope, rise, and deep- ocean basins. The majority of the sediment volume is terrigenous, but there is a higher percentage of biogenies sediments than neurotic sediments

How did the oceans form?

Water vapor from erupting volcanoes condensed and fell as rain.

Where are abyssal plains located?

between ridge systems and continental margins

What is the type of sediment with the smallest particles size?

clay

Where will you find smaller grain sediments such as silt and clay deposited?

father from shore

Why was the hypothesis that there are mermaids somewhere in the ocean not acceptable within the scientific method

it is untestable

What is a law? Give an example

principles that explain events in nature that have been observed to occur with unvarying uniformity. Gravity is an example

How old are the oldest ocean sediments? Why?

180 million years. Sediments are sub ducted at convergent boundaries

How old are the oldest sediments in the ocean? Why are there none that are older?

180 million years. They are sub ducted and convergent plate boundaries

What is the average depth of the ocean? Be sure to include units of measure

3,8000 m

Roughly, what percent of the Earth's crust is in the oceans?

70%

What percentage of the Earth's crust is covered by water?

71%

What is the percentage of water on Earth contained in the oceans?

97.5%

What is a mantle plume? What is a hotspot?

A mantle plume is a huge column of super-heated magma. A hotspot is the surface expression of a heat source (like a plume)

Why are divergent boundaries offset by transform faults?

Because the axis of spreading cannot occur in a straight line on a curved surface

What is the mechanisms that drives the movement of the continents?

Convection currents in the asthenosphere produced by heating from radioactive decay

At what types of plate boundary would we record the deepest earthquakes?

Convergent boundary, specifically ocean-ocean or ocean-continent

What are the characteristics of a transform boundary? Give an example.

Crust is neither created nor destroyed as the plates move past each other. San Andreas fault, mid- ocean ridges

What are three technologies used to measure bathymetry?

Echosounders, multibeam sonars, and satellite altimetry

Name two areas the Vikings colonized

Iceland, Greenland, North America

Where does the Mid- Atlantic ridge cross land? What are the characteristics of this area?

Iceland. The area is characterized by hydrothermal activity and volcanic activity

What is the continental rise? Where is it found?

It is formed by the accumulation of sediments at the base of the continental slope and only occurs as passive margins

What is significant about the Trieste?

It is the first submersible to reach the bottom of the Mariana trench in 1959

What was significant about the origin of the Challenger expedition?

It was the first oceanographic expedition dedicated to scientific research

What determines the density of a lithospheric plate?

It's temperature. Older plates are cooler and denser than younger, warmer plates.

Who is the lead person who discovered hydrothermal vents? What made him think they existed?

Jack Corliss. He examined rocks from the Mid- Atlantic ridge and realized they had a chemical signature that showed they had been exposed to hot water

Who reached the bottom of the Mariana trench in 2012?

James Cameron

How much of the Earth surface do the abyssal plains cover?

1/4

What is a guyot?

A seamount that reached the surface and had it's top eroded to become flat

What is an experiment?

A test that simplifies observations and is designed and carried out to see if a hypothesis is true or false

What is a seamount?

A volcanic projection that is below the surface

Marine fossils and sediments can be found throughout Alaska, yet this was never the site of an ancient inland sea. Why is this? Be sure to briefly describe the process and the term that identifies these features.

Alaska is formed out of terranes. When the oceanic plate converged with the continental plate, it was subducted and features such as islands and seamounts were 'scarped off' the oceanic plate and extended the edge of the continental plate.

What is a terrane?

An accumulation of sediment that is sheared off an oceanic plate and deposited on the edge of a continental plate at a convergence zone

What is stratigraphy?

Analysis of layered sediment deposits

When did our solar system and the oceans start to form?

Approximately 5 billion years ago

How did the Hawaiian islands form?

As an oceanic plate moved across a stationary hotspot, a series of volcanoes were formed that formed the islands

What is the difference between a constructive and destructive plate boundary?

At constructive boundaries, new crust is formed. At destructive boundaries, plate is destroyed

Where would you expect to find the smallest amount of sediment accumulation in the ocean? Why?

At spreading centers. This is the youngest crust that has just formed and there has been relatively little time for sediments to accumulate

Which of these is a testable hypothesis? Briefly explain why? a) There is no such thing as Big Foot b) all animals have eyes

B is a testable hypothesis. You can continue to examine different animals to see if they have eyes and if you find one that has no eyes, you can disprove the hypothesis. You can never fully test the hypothesis that Bigfoot does not exist because it is not possible to search everywhere at the same time to see if you observe a Bigfoot.

What are the two major ways sediments are classified?

By particle size and source

What is occurring at hydrothermal events in terms of water exchange?

Cold ocean water is seeping through fissures in the crust. When the water comes close to the magma chamber, it is warmed, then rises and boils out of the fissured near the center of the rift zone

Which portion of the continental margins has the thickest sediments?

Continental slope

True or False: Life began shortly after the 'Big Bang'. Use time points to support your answer.

False. The 'Big Bang' occurred approximately 13.7 billion years ago and the oldest known record of life is a fossil of a bacteria that is approximately 3.5 billion years old.

Someone tells you that if the water cycle breaks down and all the water from the Earth's rivers flows into the ocean and is never returned in the form of rain, the amount of water in the oceans will double. Is this true? Why or why not?

False. The oceans already contain 97.5% of the Earth's water. Freshwater accounts for 2.5% of the planet's water and rivers are only a fraction of that.

What is one property of the oceans we can measure using satellites?

Fluorescence or chlorophyll

What does authigenic mean?

Formed in the same place as the sediment now occurs

You want to find some of the thickest deposits of terrigenous sediments you can. Where would you go? Why?

Go to the mouth of a major river, like the Mississippi because rivers are the major transport mechanisms of terrigenous sediments to the ocean

What are two instruments used to collect sediments?

Grab sampler and piston corer

What are turbidites?

Graded layers of terrigenous sand embedded with smaller particles sediments that are formed by turbidity currents.

What was important contribution to knowledge that the Greek scientist Erathonese made?

He calculated the circumference of the Earth and established lines of latitude

What is significant about Fernando Magellan's voyage?

His crew circumnavigated the globe showing you could sail around the world without obstruction

Where are some of the thickest sediments in the world oceans? Why?

In the Gulf of Mexico and the Indian Ocean near the mouth of Ganges river. Rivers are the most important mechanism of transport of terrigenous sediments and so the thickest sediments are found near the largest river systems

What are the three main layers of the interior of the Earth? What is the surface layer called?

Inner core, outer core, mantle. The Lithosphere

What is one important new technology, besides satellites, that oceanographers use today?

ROVs

What is the source of heat in the Earth that keeps the asthenosphere pliable?

Radioactive Decay

What are two major areas where rates of sediment deposition are higher?

Rates of deposition are higher over the continental shelf and near the mouths of rivers

You have two samples of ocean crust that are the same age and have the same magnetite orientation. In sample A, the width of the band of rock with this distinct magnetite orientation is 1 meter and in sample B it is 2 m. Which sample likely came from the East Pacific Rise and which one likely came from the Mid-Atlantic Ridge? Why?

Sample A likely came from the East Pacific Rise. The band is wider indicating a faster spreading rate than in sample A and the East Pacific Rise has a faster spreading rate than the Mid-Atlantic Ridge.

Name two of the major oceanographic research institution in the USA

Scripps

How does sediment accumulation affect the bathymetry of a spreading center? Where are the affects more pronounced?

Sediment accumulation will smooth out the bathymetric features and it is more pronounced with greater distance from the spreading center because there has been a longer amount of time for sediment to accumulate

What are cosmogenic sediments?

Sediments of extraterrestrial origin (micro tektites)

You are working in a group taking sediment samples along a transect from a beach, into deeper water. Someone forgot to label the jars and they got mixed up so it is now not clear which sample came from which location. Based on what you know about particle size and transport, how can you arrange the samples in the correct order?

Smaller particles have a longer settling time than larger particles and so they are transported further offshore. You can look at the particle size in the samples and arrange them from largest (near shore) to smallest (furthest offshore).

What is isostatic equilibrium?

The balanced support of lighter material in a heavier, displaced supporting material.

What was the invention that made it possible to accurately calculate longitude at sea? What was significant about this invention in terms of how it worked

The chronometer. It relied on a spring, not a pendulum, and so could keep accurate time on a moving ship

Name one important invention of early Chinese ocean explorers

The compass

You are in the DSV Alvin and you are on a dive to study hydrothermal vents. You have reached the bottom, but don't know exactly where you are. The pilot starts moving forward to find the vent site. You notice that the contours of the bathymetry are getting smoother and smoother as you continue moving in this direction. Why is that? Are you going in the right direction?

The contours are getting smoother due to sediment accumulation. You are not going in the right direction. Sediment accumulation is greater with greater distance from the ridge system.

What is Bathymetry?

The contours of the ocean floor

What are the characteristics of a continent- ocean convergent boundary? What is an example?

The denser oceanic plate dives under the continental plate causing a trench, deep earthquakes, and the formation of volcanoes on the continent. Western south america, Pacific Northwest USA

What is the most important difference between the early atmosphere and the atmosphere today?

The early atmosphere lacked oxygen

What is the life form we have the earliest fossil evidence for and how old is it?

The fossil evidence is of bacteria. It is 3.5 billion years old.

You are reviewing a proposal from an oceanographer who wants funding to study past ocean conditions by studying sediments. They propose to study sediments that will tell them about conditions in the ocean before the breakup of Pangea, which began 200 million years ago. You quickly see something wrong with the proposal and recommend it not be funded. Why is this proposed study not possible?

The oldest ocean sediments are 180 million years old, so it is impossible to study sediments that are 200 million years old as they do not exist.

What is lithification? What important geological feature has been formed in this way?

The process by which sediments are converted into rock by pressure-induced compaction. Mt. Everest and the Colorado plateau have been formed in this way.

The Polynesians made stick maps of the locations of islands. What did these maps show?

The relative distance between islands, how long it took to travel, not the geographic distance.

What is an ocean basin?

The seafloor beyond the continental margin

Why do plates interactions occur?

The size of the Earth remains constant so as plates move they either interact or new crust if formed

How does particle size affect the settling velocity?

The smaller the particle size, the slower the settling velocity

What is pale oceanography?

The study of the oceans past

What is the continental shelf?

The submerged extension of a continent

What is the continental margin?

The submerges outer edge of a continent

What can seismic surveys tell us about ocean sediments?

The surveys can map the different layers of sediment

What is the theory of continental drift? What are two pieces of evidence that support this theory?

The theory that the continents are moving slowly across the Earth. The shape of the continents and similar rock and fossil deposits on different continents show how the continents used to be joined together into a supercontinent, Pangea

What is the continental slope?

The transition between the continental shelf and the deep ocean

Where did the water come from that filled the oceans? If the oceans covered 100% of the Earth's surface in the past, what is the amount (in percent) reduction of Earth's surface covered by the oceans today?

The water came from rain formed from the water vapor put into the atmosphere by volcanic eruptions. The percent reduction would be 29% (the oceans cover 71% of the Earth's surface today)

If a hypothesis is consistently supported and accepted by most scientist it is called

Theory

What are the characteristics of an active Margin? Give an example

There is earthquake and volcanic activity. Faces a convergent boundary. Narrow continental shelf. Pacific

You are about to embark on a research cruise to study sediments on the ocean floor across the Atlantic and Pacific Oceans. You will lower your sampler on a cable using a winch on the ship. You want to be able to reach the bottom to take a sample in at least half the locations. You are told that the winch that is currently on the ship has 2000 m of cable. Should you demand a different winch with a different amount of cable? What would you ask for and why?

Yes. You should ask for a winch with more cable. The average depth of the ocean is 3800 m so you will need at least that much cable to sample at least half the time.

You are asked to make an artificial sediment sample that could be classified as an ooze and weighs 100g. You are given terrigenous sediment and silicious (silicon based) material to mix together. How much silicious material do you need to use to make an ooze? What kind of ooze would it be?

You can mix together anything greater than 30 g of the silicious material to ensure the sample composition is 30% or greater of the silicious material. It would be a silicious ooze

You are taking sediment samples from a very deep part of the ocean. The surface waters at this location consistently have large blooms of coccolithophores. Do you expect to find the coccolith shells in your samples? Why or why not?

You do not expect to find the shells because due to the great depth, it is likely below the CCD and the shells would have dissolved and not been preserved in the sediment.

If you wanted take a sediment sample from a portion of the continental margin that has the highest percentage of ocean sediments concentrated into the smallest surface area of the Earth, where would you go? Would you chose to take the sample off the east coast of the United States or off California? Why?

You would go to the continental slope or continental rise. You would go off the east coast of the US because this is a passive margin and will have a continental rise where the active margin off California will lack one

What are turbidity currents?

an underwater current flowing swiftly downslope owing to the weight of sediment it carries.

Define density

mass per unit volume