MEA 200 Exam 1 Knowledge

EVIDENCE OF CONTINENTAL DRIFT - Glaciation

EVIDENCE OF CONTINENTAL DRIFT - Glaciation

Glaciers carve grooves in rock showing direction. In India Africa and South America the direction of the grooves comes from the water which would not have been possible unless they were all one continent that included Antartica. Because India is just north of the equator and doesn’t have glaciers, it suggest that India was located near the south pole.

EVIDENCE OF CONTINENTAL DRIFT - Magnetic dip angle

Magnetites in magma are moved by the earth’s magnetic field and when magma solidifies it “locks” them in place according to their orientation. Near the South Pole the lines of flux come are nearly perpendicular to the geoid. At the equator lines of flux are directly proportional to latitude so magnetites should be 0 degrees there. In India, the rocks should be 0 degrees but they have a large upward angle so it shows it was formed near the South Pole.

EVIDENCE OF CONTINENTAL DRIFT - Apparent pole wandering

The horizontal alignments of the magnetites in the rocks in North America and Eurasia point toward two different magnetic poles, which is impossible. It suggests that these continents were once joined, when brought back together they point to the same pole.

EVIDENCE OF CONTINENTAL DRIFT - Fossils

Fossils that appear to be in the “wrong place” indicate movement. For example, India should have tropical fossils but it has polar fossils

SEA FLOOR SPREADING EVIDENCE - Geomagnetism of the sea floor

Over time polarity of the magnetic field has reversed multiple times. Magnetites in magma orient based on the magnetic field. Magma rises at the ridge-line and creates new seafloor with the magnetites oriented by the magnetic field. Older seafloor shows alternating patterns of magnetite direction. They are symmetric because when magma rises at the ridge-line it splits apart old seafloor and creates two symmetric halves. This symmetry can only be described if seafloor is being created at the ridge-line.

SEA FLOOR SPREADING EVIDENCE - Age and heat measurements

If new seafloor is being created at the ridge-line the age of the rocks near the ridge-line should be younger and get older as it goes.

SEAFLOOR SPREADING EVIDENCE - Subduction Zones

When new seafloor is created, old seafloor has to be destroyed which happens at the margins of two colliding plates where one plate subjects under another one. The foil of earthquakes show a path of abut 45 degrees as the plate subjects. Then andesite volcanoes are produced and protrude through the lithosphere.

Seafloor Spreading Evidence

Subduction Zones, Age and Heat Measurements, Geomagnetism of the sea floor

Evidence for Continental Drifting

Glaciation, Magnetic Dip Angle, Apparent Pole Wandering, Fossils, Fit of the Continents,

The big island of Hawaii (the eastern-most island in the chain of Hawaiian islands) currently has an active volcano. What is the source of the magma causing this activity? Why do the other Hawaiian islands not have active volcanoes?

Hot spots are fixed features of the deep ocean basin. Hawaii the big island sits on the hot spot and the island grows in size everyday because of continuous eruptions and as magma rises. Recent evidence suggest that the hot spot may move as well.

How does the chain of islands and seamounts, extending out from Hawaii toward the Northwest, give additional evidence that the sea-floor is spreading?  Can this chain be explained in any other way?

As the plate moves over the hot spot it creates a long chain of islands and seamounts. Which helps provide evidence for seafloor spreading because islands progressively get older as you move away from the Big Island.

What is the proportionality relationship (direct or inverse) between ocean current energy and grain size for the transportation/deposition of sediment?

There is a direct relationship between ocean current energy and grain size for the transportation and deposition of sediments.

When the grain size decreases below fine sand how much energy does it take to erode the particle?

When grain size decreases below fine sand it takes more energy to erode.

Explain why it requires as much current speed to erode clay (with a grain size of 0.001 mm) as it does cobbles (with a grain size of 100 mm); i.e., what is unique about the structure of clay particles?

It takes longer to erode clay because it is very flat with a large surface/mass ratio. Which means clay particles have a great deal of surface contact and it makes it difficult for water to get between them. Cobbles have a large amount of void space and the current can easily get between them.

Explain the process by which seawater’s pH is lowered when it increases above 8.1

If pH rises above 8.1 there are not enough hydrogen ions I the water. The ocean must increase the number of hydrogen ions in order to lower the pH. In order to do this it breaks down carbonic acid molecules into bicarbonate ions or bicarbonate ions to carbonate ions.

Explain the process by which seawater’s pH is risen when it drops below 8.1

If pH goes below 8.1 there are not enough hydrogen ions in the water. To raise the pH you must put hydrogen ions back into the water. In order to do this it bonds hydrogen ions to carbonate or bicarbonate ions.

Why must we raise pH to get the CO3-- ?

In the chemical equation, you must raise the pH in order to create the chemical reaction that gives you CO3--.

Do we raise or lower the amount of CO2 dissolved in seawater to raise this pH to accomplish the purpose you determined in?

pH also is inversely proportional to CO2, so a higher pH will be associated with a lower amount of CO2.

How are temperature pressure and photosynthesis in the upper ocean necessary to change the amount of CO2  dissolved in seawater, so that pH will increase and hydrogenous calcium carbonate may be precipitated.

In the upper levels of the ocean there is higher temperature, lower pressure, and higher photosynthesis. All of these conditions reduce the level of CO2, which raises the pH and creates the chemical reaction which gives us CO3--. The higher levels of CO3-- allow more hydrogenous calcium carbonate to be precipitated.

Which abyssal sediment has the lowest deposition rate?

Abyssal clay has the lowest deposition rate. Abyssal clay deposits at a rate of 1mm/1000 yrs. Biogenous clay 1mm/1000 years. When abyssal oozes are presenting they will always dominate abyssal clay.

How does the deposition rates of calcareous and siliceous oozes change with ocean depth & water temperature?  Contrast and compare.

Below the CCD water depths too great for siliceous ooze to reach the bottom before being destroyed, and the water is so cold that cancerous ooze will not be deposited.

Using what you answered for a. and b. above, explain how the process of DILUTION allows clay to become the dominate sediment in the North Pacific,rather than one of the oozes?

1. Because siliceous ooze and cancerous ooze cannot survive the temperature or the depth the clay becomes the dominant sediment. 2) The deepest parts of the ocean have more current gyres and have less energy clay is more easily deposited.

Explain how lowering the speed of the current that is transporting sediment could result in the deposition of that sediment.

For a specific grain size, a current of a certain speed will keep the sediment in suspension and transportable; below that speed the sediment will be deposited.

For grain sizes larger than fine sand what is the proportionality relationship between ocean current energy and grain size for the erosion of sediment (once it has been deposited)?

For grain sizes larger than fine sand there is a direct relationship between energy and grain size.

FOr grain sizes smaller than fine sand what is the the proportionality relationship between ocean current energy and grain size for the erosion of sediment (once it has been deposited)?

For grain sizes smaller than fine sand there is an inverse relationship between energy and grain size.

What is the relationship between pH and hydrogen ion concentration?

pH is inversely proportional to hydrogen ion concentration

Observation

observations or measurements of things esp repeatedly measured/observed

Hypothesis

a tentative testable statement about the natural world that can be used to build more complex inferences and explanations

Testing

test outcomes by this hypothesis

Theory

after repeated testing over time strengthens a hypothesis it becomes a theory

Lithosphere

the earth’s crust and the solid portion of the upper mantle

core of the earth

molten hot core made almost entirely of metal—specifically, iron (Fe) and nickel (Ni).

Asthenosphere

the upper layer of the mantle below the lithosphere, has low resistance to plastic flow and convection is thought to occur

Isostasy

equilibrium that exists between the layers of the earth, is like blocks floating on the underlying mantle. it rises if material is removed and sinks if material is deposited.

Subduction Zone

where Earth's tectonic plates dive back into the mantle

Theory of Global Plate Tectonics

theory of drifting continentals with the spreading of the seafloor

Describe the convective flow in the asthenosphere involved in the Theory of Global Plate Tectonics

hotter magma rises and cooler magma cools and keeps the mantle malleable and allows the tectonic plate to move

Where is new oceanic lithosphere created?

the convection currents rise at the ridge-line and cause the asthenosphere to expand and when it reaches the lithosphere it lefts and cracks the crust to form the edges of two new plates. which spread from the center.

What is the evidence that convection currents in the asthenosphere rise toward the surface and cause the formation of oceanic lithosphere at the oceanic ridges?

we would expect the warmest temperatures to be at the ridge-line and to decrease as you move away from it

At what angle and to what depth does this subduction take place (what support do we get for this from the location of the earthquake foci in the subduction zone)?

the subduction zone descends at an angle of about 45 degrees and extends to a depth of at least 750 km

Why is a trench usually associated with this subduction?

subducting plate pulls the edge of the other plate down under which its subducting to create a trench

By what process are andesite volcanoes formed during this subduction?

descending crust and sediments are melted during subduction and produce a magma with a density between that of basalt and granite called andesite which ascends through oceanic or continental lithosphere to produce andesite islands or mountains

Divergent (Constructive) Plate Boundaries

boundary is found at mid-ocean ridges, where new oceanic lithosphere is created.

Transform Fault (Shear) Plate Boundaries

Fracture Zones and Transform faults are associated with lateral "cracks" in the crust that run perpendicular to the mid-oceanic ridge line.

transform vaults

the plates on either side of this fault are different, and they move in opposite directions from each other

fracture zones

The seafloor on either side of a fracture zone is part of the same plate and are, therefore, not a plate boundary.

Why is the transform fault also considered a plate boundary?

the ridge-line is offset along one of these perpendicular cracks

How are the movements of the plates on either side of fault, and on the ridge line itself, related to the theory of sea floor spreading?

As magma rises from the mantle and solidifies as new oceanic crust the plates move apart and newly formed crust pushes older crust away. This is fundamental to the theory of sea floor spreading.

What are the three types of plate collisions

oceanic-oceanic, oceanic-continental, continental-continental

What is created by oceanic-oceanic collisions?

Island Arc System

What is created by oceanic-continental collisions?

Continental Arc System

What is created by continental-continental collisions?

Continental Mountain System.

What are island arcs, and how are they formed?

a curving chain of volcanic islands occurring around the margin of ocean basins. it’s formed when the leading edge of an oceanic plate subjects under the leading edge of another oceanic plate it creates an island arc system. the subjecting plate and much of the consolidated sediment on it melt during the descent and rise as andesite magma to form volcanic islands.

If the plate also contains a continent, what kind of sea often lies between the island arc and the continent?

The sea is “carved off” of the ocean and it creates a Marginal Sea

In place of an island arc, what topographic features do andesite volcanoes produce?

Andesite Volcanoes create mountain ranges because neither are dense enough to subduct and the obducted material scraped off can add to the continent.

Where is the trench located in relation to these volcanoes?

Under the Sea Level

What was the major consequence of the subduction of the JUAN DE FUCA Plate under the NORTH AMERICAN Plate?

violent andesite volcanoes and the potential for the largest earthquakes in the world

What is a Continental Arc System?

A geological feature characterized by a chain of volcanic mountains formed on the continents edge due to continental-oceanic plate collision.

What is a Continental Mountain System?

A large mountain range or series of mountain ranges within a continent

What happens to the sedimentary rock (once a part of seafloor) that is caught between the converging continents?

oceanic lithosphere between the two plates is folded into continental mountains

Under what conditions does the sedimentary rock usually not subduct?

sedimentary rock is usually less dense than the underlying basalt so it doesn’t subduct and is folded to create mountains a continental mountain system

In the Indian Ocean, what major effect did the movement of the INDO-AUSTRALIAN Plate have on Asia?

there was a two sequence convergence. first india’s subduction under the andesite mountains creates andesite volcanoes and a continental arc system then it is folded to create a continental mountain system

What is the Hypsographic Curve?

The graphical representation of the earth’s surface elevation in relation to its area. Which typically shows that a large portion of the Earth’s surface is covered by water.

What percent of the earth's surface is beneath the ocean surface?

70%

What is the Continental Margin?

A zone of transition between the continental crust and oceanic crust. Has a shelf, slope and rise.

Continental Shelf

A gently sloping submerged part of of a continent formed by wave and current erosion during the rise and fall of sea-level throughout geologic time (mostly as a result of ice ages)

Through which parts of the continental margin are Submarine Canyons cut?

Continental Slope

Why are Submarine Canyons prominent on the slope, with secondary tributaries on the shelf?

They are formed by erosion through turbidity currents and underwater landslides and provide a natural pathway for sediment transport from the shelf to the deep sea creating secondary tributaries

Most Submarine Canyons are thought to have been cut by what process?

Turbidity Currents and avalance-like processes of sediment deposit

In what way did the trans-Atlantic cable breaks off Newfoundland in 1929 provide evidence for the mechanism that is thought to have cut these canyons?

Here the cables up-slope and closest to the shelf break were broken first, and those that crossed the continental slope at deeper depths broke later in sequence.

Why are Submarine Canyons not likely the result of rivers that flow into the sea?

Because once a river hits the ocean it loses the force necessary to create that kind of erosion

How are continental rises formed, and are they found on active continental margins?

It is created by a long period of sediment accumulation form a continent

What is a Deep Ocean Basin?

includes all seafloor between the boundaries of the KMs; underlined entirely by the basaltic crust that is covered by marine sediments

Abyssal Plain

broad flat planes extending out beyond continental slope or rise with slopes of less than 1m/km and depths of 4.5km-6km

Mid-Ocean Ridge

long underwater mountain range through the center of the ocean basins formed by the upwelling of magma.

Mid-Ocean Rise

underwater mountain range

Trench

long, narrow depressions on the seafloor

In what ocean are the most trenches found?

Pacific

Subduction Zones are at the base of what kind of continental margins?

Active Margins

Seamounts

volcanos that never extended through the surface or that quickly subsided below after becoming dormant

Tablemounts (Guyots)

wave action erodes islands and they become flat-topped

what is the difference between fringing and barrier reefs?

Fringing Reef is at the beginning where the Cora community begins to form around an active volcano. The Barrier reef is formed around the island and separate from the volcano by an enclosed lagoon

what part may sea floor spreading play in the formation of atolls?

It provides the foundation for the volcanic activity that leads to the formation of Coral atolls

What is a Coral Atoll?

An active volcano with a coral reef surrounding it separated by an enclosed lagoon

Bohr model of atom

The model where atoms are a mini solar system with he nucleus as the sun negatively charged electrons are the planets circling in layered orbits. Nucleus contains positively charged protons and neutrons.

atomic number

number of protons

cations

positively charged ions which are atoms or groups of atoms have more protons than electrons

anions

negatively charged ions which are atoms or groups of atoms which have more electrons than protons

noble gas

gases that have the max number of electrons possible at their level

covalent bond

a type of chemical bond formed between two atoms when they share one or more pairs of electrons

ionic bond

a type of chemical reaction formed between two atoms when one atom transfers electrons to another atom

Transportation

When an ocean current is strong enough  to keep a sediment particle in suspension.

Deposition

When a current slows, such that  the sediment particle can not longer be kept in suspension and is deposited on the ocean bottom.

Erosion

Once deposited, a current needs to be strong enough so that the particles of deposited sediments are re-suspended.

Lithogenous

derived from the weathering of continental rocks or oceanic volcanoes

Biogenous

derived from organism remains called tests

Hydrogenous

derived from precipitation of minerals from seawater in place

Cosmogenous

derived outer space

Spherules

fragments that are heated by air friction during transit through atmosphere and formed into spheres

What very stable compound does weathering of rocks produce?

silicate (SiO4), quartz SiO2 is mostly silicate (clay minerals)