Oceanography Exam 1 Study Guide
Where is the Earth's crust thickest? Under the sea or under the continent?
Continent
Who was Fridtjof Nansen and what was the name of the ship in which he ventured out into Arctic Circle?
He was a Norwegian Explorer who made lot of contributions from his Arctic research, especially on the currents in the Arctic Ocean. He was awarded Nobel Peace Prize for his work on behalf of displaced victims of First World War. Name of the ship in which he allowed himself and his crew to be trapped in arctic ice for three years was Fram
-------------- came up first with a map depicting the Greek's understanding of world geography
Herodotus in 450 B.C.
Who discovered a strait (passage of 500 km wide), which is located within the southern tip of South America and which bears his name?
Ferdinand Magellan
Who led the first circumnavigation of the globe?
Ferdinand Magellan, during 1519-1522
Comprises the bulk of the continents.
Granitic rock
What was the argument of Edward Forbes (1815-1854) concerning the life at sea?
He argued that given the high pressure, cold temperature and lack of light at deeper depths, marine life could not survive below 550 meters. It is called an azoic environment (lifeless)
The average height of the continents above sea level is greater than the average depth of the ocean. (a) True (b) False
(b) False
One cubic meter of which of these would weigh the most? (a) seawater (b) granite rock (c) basaltic rock (d) seabed sediment (e) mantle
(e) mantle
Compare abyssal hills, seamounts and guyots?
- Abyssal hills are domes or elongated hills that are no taller than 1000m (1km) and they are composed of volcanic rocks. - Seamounts are submarine mountains and many are volcanoes (active or extinct). They are having conical tops and steep sides and obviously should be taller than 1000 m. - Flat topped seamounts are called Guyots. Most of the Guyots are extinct volcanoes and their tops were leveled and flattened by wave erosion
What is the radius of earth?
6371 km
What is the ratio of water and earth (solid) that covers the surface of the earth?
71:29
Unit of density?
gram/cm^3 or Kg/m^3
What is the difference between Lithosphere and Asthenosphere, in terms of their physical nature?
Lithosphere, the outermost layer is an overlap of crust and the uppermost mantle. The rocks in this layer are hard, brittle and rigid. It extends 100-200km from the surface of the earth. Asthenosphere, on the contrary, is a weak layer and flow plastically. In fact 1% of the rocks in this layer is melted. This layer is analogues to bitumen or asphalt in terms of their physical properties
In terms of volume which among the following three layers hold most of the earth? Crust Mantle Core (inner core+ outer core)
Mantle
Who is considered as the father of Physical Oceanography?
Matthew Fontaine Maury
Physical separation between crust and mantle is called?
Moho
Carbonate sediments are rare in deep sea sediments because-----
No carbonate sediments can be found below CCD. In the open ocean this limiting depth is ~4500 m
Is the position of the true geological edge of a continent is almost always the same as the position of its shoreline?
No; sea level fluctuations results in drowning and exposure of the edges of the continents. Around 15000 years ago, the shoreline along our coast was 250 km farther west
As you know, Earth is layered inside. The layers have different thicknesses and densities. How do geologists know this?
Observing the speed and path of earthquake waves traveling through the earth; studying the variations in the gravitational and magnetic fields at different locations on the earth
New Andesite crust is being produced where?
On top of the Andes Mountain ranges along western boundary of South America. When Nazca plate and South American plate collide each other, the denser Nazca Plate subducts and this triggers powerful earthquakes and volcanoes along the Andes Mountain range
Name of the seminal work published by Darwin?
Origin of Species, published in 1859
Why clay deposits are most extensive in the Pacific Ocean, as against biogenous oozes?
Pacific ocean basin is old and deep (deeper than CCD), which would allow easy dissolution of CaCO3 ooze. Siliceous ooze is confined to just two horizontal bands; one along equator and other near to north and south pole (also refer to previous answer)
What are the different branches of oceanography?
Physical, Chemical, Biological and Geological Oceanography
Name of the deep-sea trench near to Florida coast?
Puerto Rico Trench
Deepest depth in Atlantic Ocean
Puerto Rico Trench having a maximum depth of 8,648 m deep
New basaltic crust is being generated where?
Right on the floor of rift valleys of Mid-Oceanic ridges
The youngest seafloor rocks are found where?
Right on the floor of rift valleys of Mid-Oceanic ridges. Fresh basaltic magma, upon coming out from earth's interior, get solidified along this rift valleys and are further pushed down along the flanks of the ridge like in a conveyer belt, by the action of gravity
What are some land-based evidence for plate tectonics?
San Andreas Fault; relatively younger Himalayas and its continued vertical growth; active volcanoes in Iceland, Andean volcanoes along western margin of South America, etc
What was the name given by Captain Cook for the Hawaiian Islands?
Sandwich Islands; in honor of the first Lord of the Admiralty, who also invented the buttered toast which has been called sandwich to the present day
Who in fact completed the ill-fated first global circumnavigation trip?
Sebastian del Cano, companion of Ferdinand Magellan
Glass industry needs ---- as raw material for their production
Silica, SiO2
After sailing around Cape of Good Hope (southern tip of Africa), -----------reached the shores of India first in 1498
Vasco da Gama, Portuguese sailor
What do these things have in common: Paleomagnetism, seafloor spreading, Pangaea, Wadati-Benioff zones, transform faults, fracture zones, seamount chains and Pacific hotspots?
We can string together all of the above under the umbrella of Plate Tectonics
Active continental margins are located along where in the Americas?
West coast
On board HMS Beagle, Darwin studied the geology and biology of which coast?
West coast of South America, including the Galapagos Islands off Ecuador
Finer materials may need disproportionally more energy for them to be dislodged from their depositional environment and put them into suspension, why?
cohesiveness of the fine clay/silt
Of extraterrestrial origin
cosmogenous sediments
What is the name of the outermost solid layer of the Earth?
crust
The settlements established by the Vikings (Scandinavians) in Newfoundland (eastern Canada) were eventually abandoned because of -------------
harsh climate: extensive buildup of sea ice that cut off the northern sea route from Scandinavia due to the onset of the Little Ice Age
Generated in place, on the spot where we find them.
hydrogenous (or authigenic) sediments
What are the exterior envelops of earth?
hydrosphere and atmosphere
What is the main process by which sediments are transported and distributed in the polar region?
ice rafting; being carried by glaciers and icebergs and when they get dissipated, the sediment load would be dumped into the sea
Give two examples for hydrogenous sediment deposits?
manganese nodules and phosphorite nodules
Where you could find more magnesium? In the crust or in the mantle?
mantle
Hawaii islands are being formed as the Pacific plate drifts slowly over a deep-seated hot spot called -------
mantle plume
Hydrothermal springs (vents) are located near
mid-oceanic ridges
Most of the sea-floor of the North Pacific Ocean is covered with
red pelagic clay. These remote and deep sea-floor is farther away from any biologically productive zones. Also, due to their depth, deeper than CCD, no carbonate oozes could accumulate in the seafloor. Only available sediment source is the red pelagic clay, being transported by wind as well as ocean currents
The sediments that were deposited farther offshore, near to the shelf break, during low stand in sea-level are called------
relict sediments
The magnetic striping of the seafloor is considered evidence of seafloor spreading and -------------
reversal in earth's magnetic polarity during an approximate interval of 100 thousand years
The premise that grain size varies systematically with water depth (coarser to finer) is valid only when ------------- is constant
sea level
What is an echo sounder?
sound pulses that reflect off the ocean floor and off sedimentary layers
Give 2 examples for shelves having above mentioned environmental settings
south Florida shelf, Bahamas and Yucatan peninsula)
What are the minimum environmental conditions for coral reefs to thrive in a continental shelf?
sunlit, warm and clear water, lack of nutrients in the water column, shallow depth
Which are the two main sources of sediment for the deep ocean floor?
terrigenous clay and biogenous oozes
Arrive in the ocean from continents via rivers
terrigenous sediments
Red clay originated from Sahara desert could travel more than 5000 km as airborne and spread along western north Atlantic ocean True or False
true
Why coral reefs thrive along the western margin of ocean basins?
warm pool of water accumulating along the western boundary of oceans; while eastern boundary of the oceans remains cooler with the presence of a cold current like California current flowing along eastern Pacific coast
As you would drive down from Tallahassee to Miami beach, concentration of carbonate sediments in the beach increases or decreases?
water getting warmer and clear towards south. Also, major rivers are missing in the south. These all conditions support the growth of corals and other carbonate secreting organisms
Comprises the actual seafloor; beneath the accumulated sediments).
Basaltic rock
The denser of the two (granite or basalt)
Basaltic rock
Who led the Challenger expedition (1872-1876)?
Charles Wyville Thomson
What is the fundamental difference between a Continental Volcanic Arc and a Volcanic Island Arc?
- Continental Volcanic Arc is formed when an oceanic plate goes underneath a continental plate. Best example is the chain of powerful Volcanoes that are situated on top of Andes Mountain ranges, which itself was formed by the subduction of Nazca plate (basalt) under south American Plate (granite) - In the case of Volcanic Island Arc formation, older and hence denser oceanic plate go underneath another oceanic plate, which is much younger and buoyant. The best examples are Japan, Philippines, Mariana Islands, Lesser Antilles, and Aleutian Islands
What would be the depth of the ocean, if an echo sent out from the hull of the ship took 10 seconds to return back. (velocity of sound in seawater ==1500m/s)
1500*10/2 ==7500m deep
Oceanographer believe the breakup of Pangaea occurred about when
165 million years ago
How many cruises did Captain James Cook conduct during the second half of 18th century?
3 cruises, 1768- 1771; 1772-1775; 1778-1779
How old is the Earth?
4.6 billion years
An early proponent of Continental Drift hypothesis whose work was not well accepted
Alfred Wegner
What is the composition of core?
Alloy of Iron & Nickel
In general, continental shelves tend to be wider in the Atlantic or Pacific? Why?
Atlantic, as the Pacific ocean is bounded by ring of fire, which includes a band of trenches
Shelf break occurs, on average, at 130m depth. But for Antarctica shelf break occurs at ~200-300m, why?
Because of the enormous weight of the Polar Ice Caps the entire Antarctic continent is submerged more to keep the equilibrium. Greenland also has a deeper shelf break
Who was the first to publish a reasonably accurate chart of the Gulf Stream?
Ben Franklin, 1769, based on the life experiences of Nantucket Whalers who took advantage of this river of water off the coast of New England area
The oozes on the seafloor mostly consist of---------- and ----------
Calcareous ooze and siliceous ooze
What is CCD?
Calcium carbonate Compensation depth. Below which water is slightly acidic and can dissolve the carbonate particles raining down from upper water column, like fecal pellets and skeletal remains of dead organisms. No carbonate sediments can be found below CCD. In the open ocean this limiting depth is ~4500 m
Who was the first mariner to sail the polar seas of both hemispheres?
Captain Cook
Who mapped the east coast of Australia first?
Captain James Cook
Who re-discovered Hawaii, New Zealand?
Captain James Cook
Who was the naturalist onboard HMS Beagle?
Charles Darwin
Ocean basin can be broadly divided into three categories. Which are they?
Continental margins, deep ocean basins and mid-ocean ridges
The heap of unconsolidated sediment at the base of the continental slope is known as
Continental rise
The transition zones between the continental shelf and the deep seafloor is?
Continental slope and continental rise
Compare the composition of crust and mantle?
Crust is made of lighter materials such as Aluminum, Silicon & Oxygen; while mantle is made of relatively dense materials such as Magnesium, Iron, Silicon and Oxygen)
The Meteor (German) expedition (1925-27) is considered as the beginning of modern oceanographic research. What was the major contribution from this expedition?
Detailed map of the South Atlantic seafloor was generated using an Echo-sounder which was invented a few years before that cruise
The mid-ocean ridges are recognized as what kind of boundary?
Divergent boundary; also called spreading centers as new basaltic seafloor is being generated along these ridges, which results in the spreading of ocean floor to either side of the ridge
How does the diameter and the circumference of the earth remains constant while new seafloor is continuously being formed along mid-oceanic ridges, which has a length of 60000 km?
Some of the lithospheric plates are undergoing subduction (shrinking) at a fast pace Ex. Pacific Plate is undergoing subduction all along its boundaries (ring of fire) and its surface area is shrinking year by year while most other ocean basins are expanding (Atlantic, Indian, Red Sea)
The Lesser Antilles Islands that boarders the eastern boundary of Caribbean Sea were formed by what process?
Subduction of South American Plate under Caribbean plate, which resulted in the formation of Volcanic island Arcs; their formation is similar to the formation of Japan, Aleutian Islands, Mariana Islands
Name of the book published by Mathew Maury, which would familiarize the general public with the available scientific findings about the ocean?
The Physical Geography of the Sea, in 1855
If two oceanic plates collide at a relatively fast speed, and one is much older and cooler (therefore denser) than the other, what will probably happen?
The older plate will subduct under the younger plate. This subduction results in the formation of power volcanoes and earthquakes. Ex. This is exactly what happens along the Mariana Trench in Western Pacific, when older Pacific Plate colliding with Philippine Sea Plate, the former is subducting.
The force that drives the movement of lithospheric plates on the earth's surface is believed to be:
Thermal convection in the asthenosphere. Also slab-pull and ridge-push should be taken into consideration
Where in an ocean basin submarine canyons are found?
These deeply incised V-shaped landforms are found along some of the Continental slope and in some instances, across shelf also
Hydrosphere consists of just 10% of the entire reservoir of water contained in the earth. Where goes the rest 90%?
They are chemically bonded to solid minerals that comprise the rocks of the crust and mantle
The Himalayas are some of the highest mountains in the world. What tectonic process created them?
They were formed along a convergent Plate boundary. Eurasian Plate and Indian Plate collided together and resulted in the formation of Himalayas. The collision is still going on and we can expect further vertical growth of this mountain range
--------are plate boundaries where ocean floor is neither created nor destroyed
Transform faults; best example San Andreas Fault
Among the following list, which one is the largest in diameter a. Coarse sand b. Very fine sand c. Silt d. clay
a. Coarse Sand
Compare the average width, depth and slope of the following features - Continental Shelf - Shelf Break - Continental Slope - Continental Rise
a. Continental shelf (average width: 60 km & slope =0.5o) b. Shelf break (average depth: 130m) c. Continental slope (average depth: 2-3 km; slope= 4.0 o) d. Continental rise (average slope: 1.0 o)
Where in the ocean would you expect least thickness for the accumulated sediments?
along mid-oceanic ridges and maximum thickness of sediments can be found at oceanic trenches
Of organic origin; i.e., made by organisms.
biogenous sediments
Oozes are
biogenous sediments
Select the finest particles in this list: a. sand. b. silt. c. clay. d. granules.
c. clay
Particle-size distribution and ------ determine the nature of sediment distribution in the ocean
energy conditions, like waves, currents etc
Name two locations on the earth where Silicious ooze dominate?
equatorial Pacific and north and south polar belts
In an Oceanic scale, Atlantic Ocean has more sediment density than Pacific Ocean. Possible reasons?
ew rivers draining into Pacific ocean, Of course ocean is vast in size, the trenches along the Pacific boundary acts as a sediment trap for the sediments that are originated from land and transporting across the shelf