Marine Science Exam 1 (Part 2)

Where is the Earth's crust thickest? Under the sea or under the continent?

Continent

The average height of the continents above sea level is greater than the average depth of the ocean. (True or False)

False

Comprises the bulk of the continents.

Granitic rock

Flat topped seamounts are called -------------

Guyots

Most of the -------------- are extinct volcanoes and their tops were leveled and flattened by wave erosion

Guyots

What is the average depth and slope of the continental slope?

(average depth: 2-3 km; slope= 4.0 degrees

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/cm3 or Kg/m3

As you know, Earth is layered inside. The layers have different thicknesses and densities. How do geologists know this?

Hint: Observing the speed and path of earthquake waves travelling through the earth; studying the variations in the gravitational and magnetic fieldsat different locations on the earth

Hydrosphere consists of just 10% of the entire reservoir of water contained in the earth. Where goes the rest 90%?

Hint: They are chemically bonded to solid minerals that comprise the rocks of the crust and mantle

________, 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.

Lithosphere

In terms of volume which among the following three layers hold most of the earth? Crust Mantle Core (inner core+ outer core)

Mantle

One cubic meter of which of these would weigh the most? (a) seawater (b) granite rock (c) basaltic rock (d) seabed sediment (e) mantle

Mantle

Where you could find more magnesium? In the crust or in the mantle?

Mantle

Physical separation between crust and mantle is called?

Moho

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

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 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.

--------------- are submarine mountains and many are volcanoes (active or extinct)

Seamounts

Have conical tops and steep sides and obviously should be taller than 1000 m

Seamounts

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 etc

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

What is the average width and slope of the continental shelf?

average width: 60 km & slope =0.5 degrees

How 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?

hint: Some of the lithospheric plates are undergoing subduction (shrinking) at a fast pace. E.g., 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). Mediterranean Sea is another example for widespread shrinking and it is in a terminal state

What are the exterior envelops of earth?

hydrosphere and atmosphere

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

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

Comprises the actual seafloor; beneath the accumulated sediments

Basaltic rock

The denser of the two.

Basaltic rock

What is the average slope of the continental rise?

1.0 degrees

What is the average depth of the shelf break?

130 m

Oceanographer believe the breakup of Pangaea occurred about when:

165 million years ago

How old is the Earth?

4.6 billion years

---------------- are domes or elongated hills that are no taller than 1000m (1km) and they are composed of volcanic rocks

Abyssal Hills

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

__________ 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

Asthenosphere

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. The Big island of Greenland also has a deeper shelf break

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). Another example is the subduction of Juan de Fuca plate under the North American plate created a chain of volcanoes along Washington and Oregon States (Pacific North West of USA). 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 etc

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

What is the name of the outermost solid layer of the Earth?

Crust

______ is made of lighter materials such as ________, Silicon & Oxygen; while ______ is made of relatively dense materials such as ________, _______, Silicon and Oxygen

Crust; Aluminum; mantle; Magnesium; Iron

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 is exactly what happens along the Mariana Trench in Western Pacific, when older Pacific Plate colliding with Philippine Sea Plate, the former is subducting. This subduction results in the formation of power volcanoes and earthquakes which culminated in the formation of Mariana Islands, including the US territories of Guam and northern Mariana Island Archipelago. The genesis of Antilles Island chain along eastern Caribbean Sea can also be explained in the same way

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

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

Where in an ocean basin submarine canyons are found?

along some of the Continental slope and in some instances, across shelf also. Eg. Hudson Canyon (NY/NJ), Desoto Canyon (Pensacola/FL)