Oceans 1 - Ch 1-4

Select all the statements below that are true regarding continental and oceanic crust.

- Oceanic crust is denser than continental crust. - Oceanic crust is largely composed of basalt.

The Mohorovičić discontinuity (the Moho) is the upper surface of the ______________.

mantle

What happens to the majority of terrigenous sediments deposited on the continental margins?

They are moved seaward and down continental slopes by waves, currents, and turbidity flows.

Identify the ways in which ocean sediments can be used as direct evidence in solving different type of issues.

To map offshore pollution patterns To identify sites for underwater construction projects To find offshore mineral resources

Marine sediments are classified according to grain ________ , geographic location, and origin and composition.

size

The difference between surface and body waves is surface waves ______.

travel at the surface of Earth and body waves travel within Earth

Earth's magnetic field consists of ______ opposing pole(s). This is called a ______.

two; dipole

Cores are the _________.

vertical, cylindrical samples of sediment and rocks obtained by drilling

The Hawaiian Island chain is the result of a ______.

volcanic hotspot

Lithogenous particles are transported to the ocean by means of ______.

water gravity wind ice

The energy that is released when an earthquake occurs travels though Earth in the form of vibrations known as seismic _____________.

waves

Cores taken near the oceanic ridges show the age and thickness of the sediment increases as you move away from the ridge. This supports seafloor spreading because it indicates the ______.

younger crust nearest the ridges has not been around long enough to accumulate the same thickness of sediment as sections farther out did

The oldest rocks in the ocean (about 200 million years) are much __________ than the oldest rocks on the continents.

younger/newer

Select all the evidence the Glomar Challenger provided to support the theory of seafloor spreading.

- Sediment age and thickness increases outward from the ocean ridge system. - No oceanic crust older than 180 million years was found.

Select all the lines of evidence Wegener used to support his theory of continental drift.

- geographic fit of continents - fossils of plants/animals - pattern of glaciation

The theory that describes the movement and fragmentation of the lithosphere into seven major plates along with a number of minor ones is called ______.

continental drift

Manganese nodules are considered a valuable resource from the ocean floor because they are abundant and contain not only manganese but also ______.

copper, nickel, cobalt

As a new volcano quickly grows, its elevation may ___________ because its weight depresses the crust underneath it.

decrease

At convergent plate boundaries, the tectonic plates are moving toward each other. What happens at these boundaries depends heavily on the ______ of each plate.

density

The Wadati-Benioff zone is the ______.

dipping zone of seismicity at subduction zones

New oceanic crust is created at some ______ boundaries, as the plates move in opposite directions.

divergent

Match the sampling device with the description of how it is used to obtain ocean sediment.

dredge - A net or basket dragged across the sea floor grab sample - Hinged device that obtains a sample from a specific location on the sea floor corer - Long barrel that obtains continuous and undisturbed sediment layers

A continental _____________ zone is associated with mantle upwelling, crustal weakening, and extensional forces.

drift

Seismic waves travel though Earth. The waves form when ______.

earthquakes occur

Since hotspots operate independently of the plate tectonic system, they are not useful for studying plate motion.

false

True or false: Seabed resources have only recently been exploited (beginning in the mid-1900s) because their mining required modern technological devices.

false

The point within Earth where an earthquake occurs is called the _________ , and the point on Earth's surface directly above this location is called the __________.

hypocenter, epicenter

Abyssal clay is often called red clay because these pelagic sediments are rich in the element _______

iron

When two oceanic plates converge, the plate with a greater density will subduct. This plate will partially melt, causing the formation of a line of volcanoes on the overriding plate. This line of volcanoes is called a(n) ______.

island arc

The principle of __________ describes the balance of forces between internal pressures in the lithosphere and mantle. It allows for the less dense continental material to float on the denser mantle.

isostacy

What is the name of the process through which loose sediments on the sea floor are transformed into sedimentary rock?

lithification

The mineral magnetite in basalt aligns itself with the ______ field of Earth before the molten rock material cools past the Curie temperature.

magnetic

The study of ocean basin history through the analysis of sediments is called ________.

paleoceanography

If you were to study _______ , you would study the magnetism of ancient rocks.

paleomagnitism

The relatively calm trailing edge of continents are called ______ margins, while the leading edge of continents are called ______ margins.

passive, active

A convection cell in the mantle is the ______.

pattern of movement mantle material takes as it heats and cools

Each lithospheric ______________ consists of the upper 80 to 100 km of rigid mantle rock and is topped by either oceanic or continental crust.

plate

If you know the age of the rocks on a particular seamount and the distance it is from its associated hotspot, you can determine the rate of _____________ motion

plate

To classify sediments as lithogenous means that they are derived from ______.

preexisting rocks

The P-wave shadow zone (where the waves are not felt at the surface of Earth) is caused by the waves being ______ by the liquid outer core.

refracted

A polar _________ occurs when the north magnetic field and the south magnetic field switch orientations.

reversal

The mid-ocean _______ and ________ systems are the most notable features of the ocean floor.

ridge, rise

Hotspot volcanoes are likely the result of ______.

rising magma from the mantle

Transform boundaries occur where two tectonic plates _____ past each other. This motion does not always occur freely, and thus _______ faults are formed.

slide, transform

As seismic waves travel from one medium to another, they are likely to refract because their _________ changes as they enter a new material with different physical properties.

speed/velocity

______ minerals are formed on the ocean floor when hot seawater laden with minerals pours out from rifts and hits the cold ocean water, quickly precipitating the metals.

sulfide

The thickest deposits of ocean sediment are generally found near ______.

the continental margins

Continental drift is the theory that ______.

the continents are slowly moving about Earth's surface

A sounding is a measurement of ______.

the depth of the ocean

Seafloor spreading is ______.

the lateral movement of the oceanic lithosphere near spreading centers

Basalt, the most common rock of the oceanic crust, can record the orientation of the magnetic field at the time of its formation because ______.

the magnetic mineral magnetite aligns itself with Earth's magnetic field before the molten rock fully cools

A lithospheric plate is composed of ______.

the upper rigid mantle (80 to 100 km) capped by either oceanic or continental crust

Body waves change direction (refract) within Earth mainly because ______.

their speed changes as they move between materials with different physical properties

The ______ of oceanic lithosphere increase(s) with a rate proportional to the square root of its age.

thickness

Phosphorite is a seabed resource used ______.

to produce fertilizers

Rank Earth's layers by their average densities

1. crust 2. mantle 3. core

The San Andreas Fault in California is an example of a long ______ fault.

transform

Select the statements below that are true regarding polar reversals.

- After the reversal, the magnetic north and south poles have switched positions. - The magnetic fields appear to weaken before the reversal occurs.

All the characteristics listed below apply to either P- or S-waves (body waves). Select all the items that apply to P-waves.

- Can travel in a liquid - Are compressional waves - Travel the fastest

Select all the causes below that correctly describe why transform faults may occur.

- Collisions between sections of the lithosphere - Changes in speed and direction for plates as they move on a spherical surface - Variations in strength or location of convection cells in Earth

Select the two ideas below that plate tectonics incorporates and builds upon.

- Continental drift - Seafloor spreading

The abyssal plain, or flat portion, of the sea floor is littered with hills and mountains, many of which are volcanic in origin. Which of the following are the names of some of these features?

- seamounts - guyots - abyssal hills

Match the layer to its description. - crust - mantle - core

- thinnest, outermost layer - thickest, middle layer - inner layer, second thickest

What percent of marine sediment is terrigenous?

75%

Which of the following are sources of lithogenous particles in the ocean?

Ash from volcanic islands Rocks transported by icebergs Windblown dust

______ sediments are derived from organisms.

Biogenous

The position of north and south magnetic poles is constant over human time scales.

False

Marine sediments are classified using which of the following three characteristics?

Geographical location Size Origin and composition

How does the carbonate compensation depth (CCD) affect accumulation of calcareous ooze on the ocean floor?

Ooze accumulates at depths above the CCD. Ooze does not accumulate at depths below the CCD.

Which of the following describe neritic sediments?

Originate from rocks on land Transported by rivers to the ocean Found near continental margins

What resource is the most commonly sought after (in terms of volume) on the sea floor?

Sand and gravel

Which of the following correctly describe sand and gravel resources found on the sea floor?

Sand is mined as a source of metals. Sand and gravel is mostly mined for use in construction.

Assuming an isostatic balance beforehand, what adjustment will occur if rock is removed from the continental crust via erosion?

The continental crust will rise.

Select the statement below that describes the average age of the rocks that comprise the oceanic and continental crust.

The oceanic crust is generally younger than the continental crust.

What do we call the dipping pattern of seismicity at subduction zones?

Wadati-Benioff zone

Which of the following describe weathering of the sea floor?

Weathering is more rapid along coastlines. Weathering occurs more slowly than on land.

Earth's magnetic field is similar to what would be expected if a giant bar magnet was located within Earth. It is aligned ______.

about 11.5ο off Earth's axis of rotation

The youngest sea floor can be found ______.

at spreading centers

The majority of the earthquakes in the world occur at or near the ______.

boundaries of tectonic plates

Physical weathering of the ocean floor occurs primarily ______, whereas dissolution of minerals dominates chemical weathering.

by waves and currents

Given the right conditions, ______ carbonate in tests will dissolve in ocean water. The depth at which this dissolution first begins is called the lysocline.

calcium

The ______ is the depth at which the amount of calcareous material preserved falls below 20% of the total sediment.

carbonate compensation depth (CCD)

Magnetic reversal are most likely associated with ______.

changes in the motion of material in Earth's liquid outer core

The deep-sea floor receives a ______ supply of sediment.

constant but slow

The Himalaya Mountains are the result of a ______ convergence.

continent-continent

The idea that the continents are slowly moving about Earth's surface is called ______ drift.

continental

Match the term to its correct definition.

continental margin - Where land meets the ocean Passive margin - Where the continent-land transition is not a plate boundary Active margin - Where the continent-land transition is a plate boundary Continental shelf - The submerged flat borders of the continent that slope very gently away from the shoreline

In which location are most neritic sediments found?

continental shelf

Primarily composed of granite, ________ crust has a lower density and is thicker than _________ crust, which is primarily composed of basalt.

continental, oceanic

The vertical, cylindric rock sections that are obtained by drilling into the sea floor are called ______.

cores

The two major models for a mechanism to drive plate tectonics are the ridge-push, slab-pull and the convection models. The convection model relies on ______ between the top of the convecting cell and the base of the lithospheric plate, and the push/pull model relies on the ridge ______ and pushing the plate outward as the ridge falls in elevation.

friction; cooling

We know Earth has a layered internal structure ______.

from models constructed using the differences between P- and S- wave travel times and their shadow zones

The pattern of heat flow near ocean ridges is ______.

greatest near the ridge and generally decreases as you move outward from it

The pattern of heat flow near ocean ridges is __________

greatest near the ridge and generally decreases as you move outward from it

The Hawaiian Islands to the west of the main island have inactive volcanoes because they have moved off of the ________.

hotspot

Gas ________ are solid, icelike structures composed primarily of methane that are formed in high-pressure locations such as the deep-ocean floor.

hydrates

Beneath the crust is the mantle. The upper surface of the mantle was identified by the change in seismic properties resulting from the increased density of the rocks there. This upper surface of the mantle is called the ______.

moho

Sediment smaller than 0.0625 mm in diameter cannot be seen unaided and is called ________. Sediment between 0.0625 and 2 mm in diameter generally is known as ______, and grains larger than 2 mm are called _________.

mud, sand, gravel

Spreading centers are where new ______ lithosphere is created, and ______ zones are where older oceanic crust descends into the mantle and is recycled.

oceanic; subduction

Of all seabed resources extracted from the sea floor or below, ______ represent more than 95% of the value.

oil and gas

Pelagic sediments with over 30% biogenous material are known by the general name of __________.

ooze

Biogenous sediments are derived from ______.

organisms

The lateral movement of the oceanic lithosphere near ocean ridges is called seafloor __________ .

spreading

The areas in which new sea floor and oceanic lithosphere are formed are called ________ centers, and the areas where older oceanic lithosphere is recycled as it descends and melts are called zones.

spreading, subduction

The S-wave shadow zone (where the waves are not felt at the surface of Earth) occurs at an angular distance greater than about 1040 from the location of an earthquake because the waves are ______.

stopped by the liquid outer core

Generally, ______ are the type of seismic waves that cause the most damage.

surface waves