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105 Cards in this Set

  • Front
  • Back

Asthenosphere

Hot, partially melted, slowly flowing layer of upper mantle that the lithosphere floats on.

Basalt

the relatively heavy crustal rock that forms the seabeds, composed mostly of oxygen, silicon, magnesium, and iron.

Buoyancy

the ability of an object to float in a fluid by displacing a volume of that fluid equal in weight to that of the floating mass.

Conduction

A process of slow migration of heat through the mantle and into the crust.

Continental Crust

The solid masses of the continents, composed primarily of granite.

Continental Drift

The theory that the continents move slowly across the surface of the Earth.

Convection

a fluid is heated, becomes less dense, and rises.

Convection Current

slow-flowing circuits of material within the mantle.

Convergent Plate Boundary

two plates move toward each other and interact, oceanic crust subducts and get destroyed. Earthquakes are common as well as volcanoes on the subduction side.

Core

The innermost layer of Earth, composed primarily of iron with nickel and heavy elements. The inner core is thought to be solid 6,000 degrees celsius. Outer core is 5,000 C liquid mass.

Crust

The outermost solid layer of Earth, composed mostly of granite and basalt; the top of the lithosphere.

Density

the mass per unit volume of a substance, usually expressed in grams per cubic centimeter.

Density Stratified

the formation of layers in a material, with each deeper layer being denser than the layer above.

Divergent Plate Boundary

two plates move apart from each other, oceanic crust forms. (mid-ocean ridges/spreading centers)

Echo Sounders

devices that measure depth by bouncing high-frequency sound waves off of the bottom.

Fault

When the force of uplift or down bending exceeds the mechanical strength of the adjacent rock, the rock fractures along the plane of weakness.

Granite

the relatively crustal rock-composed mainly of oxygen, silicon, and aluminum-that forms the continents.

Hot Spot

one of the surface expressions of plumes of magma rising from relatively stationary sources of heat in the mantle. As a plate passes over a hot spot, it weakens, forms a volcano, and since the plate is still moving it becomes inactive and a new volcano forms.

Isostatic equilibrium

the balanced support of lighter material in a heavier, displaced supporting matrix; analogous to buoyancy in a liquid.

lithosphere

The brittle, relatively cool outer layer of Earth, consisting of the oceanic and continental crust and the outermost, rigid layer of mantle.

Lower Mantle

the rigid portion of Earth's mantle below the asthenosphere. Doesn't melt due to increased pressure, denser, flows slower.

Magma

lava when it is above ground.

Magnetometer

measures the amount and direction of residual magnetism in a rock sample.

Mantle

The layer of Earth between the crust and the core, composed of silicates of iron and magnesium. 68% of earth's mass.

Mantle Plume

continent-sized columns of superheated mantle originating at the core-mantle boundary.

Oceanic Crust

The outermost solid surface of Earth beneath ocean-floor sediments, composed primarily of basalt.

Pacific Ring of Fire

a circle of violent geographical activity surrounding much of the pacific ocean.

Paleomagnetism

Frozen magnetic field, remnants of when it was magma.

Pangea

Name given by Wegener to the original 'protocontinent' The breakup of Pangaea gave rise to the atlantic ocean and to the continents we see today.

Panthalassa

Name given by Wegener to the ocean surrounding Pangaea.

Plate

one of about a dozen rigid segments of Earth's lithosphere that move independently. The plate consists of continental or oceanic crust and the cool, rigid upper mantle directly below the crust.

Plate Tectonics

the theory that Earth's lithosphere is fractured into plates that move relative to each other and are driven by convection currents in the mantle.

Radioactive Decay

a process that generates heat when unstable forms of elements are transformed into new elements.

Radiometric Dating

uses unstable, radioactive elements that lose particles from their nuclei and ultimately change into new stable elements. Decays at a predictable rate.

Richter Scale

A logarithmic measure of earthquake magnitude. A great earthquake measures above 8.

Rift Valley

A linear lowland between mountain ranges usually caused by crustal extension.

Seafloor spreading

1) if the new oceanic crust cooled as it moved from the spreading center, it should shrink in volume and become denser, and the ocean should be denser farther from the spreading centers.


2) if the mid-ocean ridges were spreading centers and sources of new ocean floor rising from the asthenosphere they should be hot.


3) sediments at the edges of the ocean basin should be thicker and older than those near the spreading center.

Seismic Waves

low-frequency pulses of energy generated by the forces that cause earthquakes.

Seismograph

An instrument that senses and records quakes.

Spreading Center

located at mid-ocean ridges, where new crust is formed.

Subduction

Where the Earth's crust plunges below another piece.

Subduction Zone

Wadati-Benioff zones; where subduction occurs.

Superplume

Largest known plume; lifting all of Africa

Terrane

the plateaus, isolated segments, ocean ridges, etc are squeezed and sheared onto the face of a continent.

Transform Fault

A plane along which rock masses slide horizontally past one another.

Transform Plate Boundary

two plates slide laterally past each other. Neither destroyed or created.

Wegener, Alfred

Proposed theory of continental drift in 1912.

Wilson, John Tuzo

Plate tectonics in 1965

Wilson Cycle

Life cycle of a plate; 1)continental crust is pushed from below it arches and fractures, 2) broken pieces are pulled apart and the spaces are filled with new oceanic crust 3) at the new spreading center magma rises into the crustal fractures 4) some magma solidifies in the fractures, some erupts from volcanoes.

Francis Bacon

1920s he noticed that coastlines looked like they could fit together. (south atlantic)

When did pangaea break apart?

200mya

Edward Suess

1885 he looked at fossil records across continents.w

Richard Oldham

1900 seismic waves and earth is layered.

Hugo Benioff

1940 plotted deep earthquakes around pacific plate.
Hess
1960 contintents would be pushed aside, motion could be powered by convection currents.

Ocean-ocean crust convergence

One plate is older so it subducts.

continent-continent crust convergence

since both plates are equal density they push against each other and form mountains by compressing.

Matthews

1963 symmetrical magnetic stripes on both sides of a spreading center.

What force did Wegener believe was responsible for the movement of continents?

He proposed that due to centrifugal force the sun and moon pulling, and the tidal currents, that the continent Pangaea was slowly pulled apart.

What were the greatest objections to Wegener's hypothesis?

By far the greatest objection was due to how we viewed the mantle and core of the Earth. They were thought to be completely solid and unmovable. There was also no 'evidence' in the seafloor.

What do we mean when we say something is dense?

Density is mass divided by volume. The higher mass to volume ratio means the faster it will sink, and or the lower in the Earth you will find it.

How is density expressed?

grams per cubic centmeter

How can seismic waves be used to 'see' inside of Earth?

seismic waves can be measured from different sides of the Earth because they go through the Earth. This means that the sped and direction that the sound frequency travels can tell us what's in the center. If it's homologous it would travel in straight lines, if it gradually gets denser towards the center, the vectors would bend, and if it has distinct layers you would have straight, bent, and refracted.

List Earth's internal layers by physical characteristics.

the lithosphere is the crust and upper mantle. It's brittle, cold, and floats on the asthenosphere (upper mantle) which is molten and flows. The mesosphere, denser than the upper mantle and flows slowly due to higher pressures. Lastly there is the core which is extremely hot, dense, and half liquid (outer), half solid (inner). The core also rotates eastward slightly faster than the mantle.

What is the relationship between the crust and lithosphere? Between the lithosphere and the asthenosphere?

the lithosphere includes the crust and it rigid. It floats on the asthenosphere which is directly beneath it supporting from below.

Why is Earth's interior still hot? Shouldn't it have cooled off by now?

The Earth is still hot because while the radioactive decay no longer occurs in the core, it's still happening in the crust and upper mantle.

How can continents be supported high above sea level?

continents work just like a ship on the ocean, they are buoyant on the asthenosphere where they displace their mass beneath the crust. The larger the continent the lower in the mantle it floats.

How did a careful plot of earthquake locations affect the discussion of the theory of continental drift? What about the jig-saw puzzle-like fit of the continents around the atlantic?

the plot showed lots of seismic activity around lines such as the mid-atlantic ridgeline and the ring of fire. This hinted that there has been separation activity, i.e. the coasts used to be a lot closer, thereby needing a method.

How did an understanding of radioactive decay and radiometric dating influence the debate?

The radioactive decay allowed researchers to develop radiometric dating. They used this to determine the age of the center of the continents and the center of the ocean. The center of the ocean was dated less than 200 may whereas the center of the continent was dated around 4 bya.

What were the key insights that Hess and Wilson brought to the table?

Hess explained seafloor spreading and Wilson continental drift into the plate tectonic theory theme.

Can you outline, in very simple terms, the action of Earth's crust described by the theory of Plate tectonics?

The plate tectonic theory states that the 12 plates all move, floating on the asthenosphere (influenced by the mantle's convection currents) in relation to one another either by convergence, divergence, and/or transvergence.

What kinds of plate boundaries exist? Can you tell what happens at each? Provide examples.

The plate boundaries are divergent (mid-atlantic ridge), convergent (mariana trench), and transform (san andreas fault). When boundaries are divergent, the mantle creates new oceanic crust to fill in the hole. On continents this creates new oceans. At a convergent boundary, the denser plate suducts, loses its water and carbon dioxide and becomes the mantle again. Sometimes the water and CO2 make gaseous magma and come out of volcanoes. At transform boundaries, the plate is moving laterally from its neighbor causing faults and earthquakes when it overcomes friction to move.

About how fast do plates move?

Spreading is about 7 inches along parts of the pacific plate, however most do abut 1.3 inches a year.

What causes earthquakes and volcanoes?

A convergent boundary causes them from the sweat off of a subducted plate and earthquakes are the cause of downward lurches.

Is Earth's magnetic field a constant? That is, would a compass needle always point north?

Earth's magnetic field actually changes by reversing polarity every now and then. A compass needle always points magnetic north, not true north.

How can Earth's magnetic field be 'frozen' into rocks as they form?

at a spreading center, new oceanic crust is always being made. The special thing about this crust is that it has a magnetite that aligns with the magnetic polarity of the time that it cools and then remains as such. Paleomagnetism.

Can you explain the matching magnetic alignments seen south of Ireland?

as the plates pull apart, the new magma captures the magnetic fields polarity and spreads etc forming bands of matching magnetic alignment.

How does the long chain of Hawaiian volcanoes seem to confirm the theory of plate tectonics.

The islands are formed from volcanoes above a hot spot. Sine there are more tan one island t shows that the plate these islands are on are moving, other islands show the same movement.

Earth is 4,600 million years old, and the ocean nearly as old. Why is the oldest ocean floor so young? Rarely more than 200mya?

The oceanic crust, unlike continental crust, is cold and dense so it subjects under the continental crust. Recycling the old crust for the new.

Do you live on a terrane?

No, however if I lived in western america I might.

What is the theory of plate tectonics?

the theory that Earth's lithosphere is fractured into plates that move relative to each other and are driven by convection currents in the mantle.

What are some of the geological characteristics of plate tectonics?

mid-ocean ridges, mountains, deep sea trenches, volcanoes, earthquakes.

How can the age of the seafloor be determined?

radiometric dating and/or by the paleomagnetism and what we know about the time periods it occurred.

How do lithospheric plates form and move?

they form at divergent boundaries where oceanic crust is created and they get moved by the convection currants in the mantle as well as the down pull of the subducted side of the plate.

What are the three types of plate boundaries?

divergent, convergent, and transform

Which boundary is associated with mid-ocean ridges?

Divergent boundary

Where do the deepest earthquakes occur?

On the leading edge of a subducting plate.

What style of boundary is the San Andreas Fault?

Transform

Do you need EQ insurance in Madison? Why?

No because we are not located near a subduction zone.

How is the Earth's magnetic field created?

it is generated by a geodynamo (the movement of the molten outer core)

What is the continental drift hypothesis?

the continents move slowly across the surface of the Earth.

How did the fossil record play into the hypothesis?

Suess discovered what looked like zones that fossils derived from in an ancient pangaea.

How does continental drift differ from plate tectonic theory?

continental drift is the floating of the continents but doesn't have a mechanism, Holmes in 1929 explained how continental drift occurred, plate creation and destruction, as well as the mechanism.

How did magnetism play into the formation of PT theory?

Magnetism showed evidence of seafloor spreading and the drifting of the continents.

How did the mid-ocean ridges play into the PT theory?

helped provide evidence with bands of paleomagnetism fossil records.

On what points was Wegener correct? Wrong?

Wegener understood that there was indeed movement of the continents and plates however he did not have a mechanism.

How are Earth's internal layers classified?

chemically (crust, mantle, inner and outer core), or physically (lithosphere, asthenosphere, mesosphere, core)

How is crust different from lithosphere?

The lithosphere encompasses the crust as well as the upper, rigid mantle.

Where are the youngest rocks in the seabed? The oldest? Why?

The youngest rocks are found at the divergent boundaries where new crust is being formed. The oldest, being the furthest from the boundary are right next to the subduction zones.

Would the most violent earthquakes be associated with spreading centers or with subduction zones? Why?

They would be associated with subduction zones because the friction between the subducted plate and the continental plate would be huge compared to the creation of new plate.

Describe the mechanism that powers the movement of the lithospheric plates.

the mechanism that powers the movement is convection currents in the mantle. These push up and spread the divergent boundaries and pull down the subducted plates with gravity.

Why is paleomagnetic evidence thought to be the 'lynchpin' in the plate tectonics argument? Can you think of any objections to the matthews/vine/morley interpretation of the paleomagnetic data?

It is considered thus because we can see distinct bands of growth from the mid-ocean ridges. I could object and say that the earth just cooled that way.

What biological evidence supports plate tectonic theory?

looking at where fossils were found we can piece together the continents.

What evidence can you cite to support the theory of plate tectonics? What questions remain unanswered? Which side would you take in a debate?

I can cite paleomagnetism, fossil records, coastal observations, the red sea, trenches, earthquakes, etc. Why do mantle plumes form? How far does the plate descend? I would take the support for the theory in a debate.

Why are the continents about 20 times older than the oldest ocean basins?

The oceanic crust ALWAYS subducts under a continental crust and even when continents collide they just create mountains. Whereas oceanic crust disappears after about 200 million years back into the mantle.