Chapter 3: The Sea Floor and Its Sediments

___ margins commonly are marked by volcanoes and earthquakes, whereas ___ margins have little, if any, tectonic activity.

Active; passive

On his famous voyage on the Beagle, ___ made observations that led him to be the first to describe and publish how atolls are formed.

Charles Darwin

Match four types of deep-sea clays to origin

Chlorite - common high latitudes Kaolinite - more abundant in tropics vs polar Montmorillonite - volcanic materials Illite - Northern Hemisphere

Calcareous ooze composed primarily of three different tests. Match

Coccolithophorids - very small covered with calcareous plates; phytoplankton Pteropods - snails up to 1 cm Foraminifera - amoebal=-like - up to 1mm

Put the following coral reef structures in their natural order of formation, with the feature that forms first on top.

Fringing reef Barrier reef Atoll

The modern sounding technique illustrated here measures the ___, which then can be used to determine the depth to the ocean floor.

Sea-surface elevation

The east coast of the United States is a(n) ___ continental margin.

Passive

Match the modern sounding technique to its correct description of how it measures oceanfloor depth and features.

Remotely operated vehicles (ROVs) - Directly measure small-scale features Satellite measurements of sea surface elevation - Reflect the changes in Earth's gravity field due to sea floor bathymetry Airguns with hydrophone arrays - Measure the time for a sound pulse to reach and return from the ocean floor, using a modern echo sounder

What features of the ocean floor are over 40,000 miles long and ard found running through every ocean?

Ridge and rise systems

Most ___ and ___ systems, such as the Mid-Atlantic Ridge and the Pacific-Antarctic Ridge, are found in the middle of ocean basins.

Ridge; rise

Match the sounding technique to its description.

Rock attached to a long rope - Was the earliest known technique Cannonball attached to a piano wire - Used a premeasured length of rope and mechanical device to measure the time taken to reach the ocean floor Echo sounder - Measured the time for a sound pulse to make a round trip from a ship to the ocean floor and back

What is the general, one-word name given to the deepest areas of the ocean floor?

Trenches

___ currents are dense, fast-moving avalanches of water and sediment that flow down continental slopes, creating and deepening submarine canyons. They also bring a lot of sediment to the edge of the deep-ocean floor.

Turbidity

The two most important agents of physical change on the sea floor include the constant rain of sediment and ___.

Volcanism

Which of the following describe weathering of the sea floor?

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

True or false: Satellite altimetry measures ocean depth directly.

False

Match the sea floor terms with the appropriate definitions.

Abyssal plains - The flat, deep portions of the ocean floor Seamounts - Steep-sided volcanoes on the ocean floor that may breach the surface Abyssal hills - Very common features, less than 1000 m high Guyots - Flat-topped, underwater features found at least 1000 m below the surface

Which of these features is not part of the continental margin?

Abyssal plain Continental stairs

Which of the following describe continental slopes? (Choose all that apply)

Are steep Might have submarine canyons Can link the continental shelf with the deep-ocean floor

A submarine ___ is a steep-sided, V-shaped, large-scale feature of the continental slope.

Canyon

Put the following features in order by how much total ocean-floor area they cover, with the most common on top.

Basins Ridges, rises, and plateaus Continental shelves and slopes Trenches, seamounts, and abyssal hills

Put the following sediments in the correct order according to size, largest on top and smallest on bottom

Boulder Pebble Sand Silt Clay

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

By waves and currents

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

This feature is located at the base of the continental slope and has a more gentle gradient than the slope. It is formed by sediments that are carried down the slope.

Continental rise

Starting at the beach and moving seaward, put these features in the correct order in which you would encounter them (assuming you could walk on the sea floor)

Continental shelf, shelf break, slope, rise

Silicious ooze composred primarily of two different tests. Match

Diatoms - phytoplankton Radiolarians - zooplankton

True or false: Because they are under water, continental shelves are considered to be part of the ocean crust.

False

Put the sounding techniques in the correct order according to when they were first used, with the oldest technique on the bottom and the youngest on the top.

Echo sounder Cannonball attached to piano wire Rock attached to rope

Which of the following conditions are necessary for the formation of an atoll?

Either ocean levels rise or the volcani island subsides Coral initially grows around a volcanic island in a fringing reef

Satellite altimeters measure the ___ of the sea surface, which is then used to determine the topography of the ocean floor.

Elevation

Match the following coral reef structures to their correct descriptions.

Fringing reef - Coral growing adjacent to an exposed seamount Barrier reef - Coral found surrounding a seamount but separated from the land by a lagoon Atoll - Coral found independent of land in a ring shape

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

Geographical location Size Origin and composition

A turbidite is a ___ deposite of sediments created by a turbidity current.

Graded

Lithogenous particles transported to ocean by

Gravity, water, wind, ice

High elevation features on the ocean floor draw water toward them because they have more mass, resulting in a relatively ___ relevation of the sea surface above them. On the other hand, depressions on the ocean floor have ___ mass and gravitational attraction, resulting in depressings on the sea surface above them.

High; Less

Neritic sedimentation rates ranking, highest at top

Large river estua]ries Quiet bays Continental shelves

Distribution of deep-sea clays reflects ?

Latitude, climate

The first detailed map of the ___ floor was created in the 1950s.

Ocean

The thickness, composition, distribution, and source of ___ provide oceanographers with valuable information on how Earth functions over long time scales.

Ocean sediments

South America has both an active continental margin and a passive continental margin. These margins can be characterized by the width of their continental shelf. Where is the passive continental margin located?

On the east coast (Atlantic coast)

What two mineral types dominate composition of lithogenous sediments

Quartz, clays

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 Abyssal hills Guyots

The standardized length of a fathom is ___ feet.

Six

Measurements of ocean depth have occurred using various techniques for over 2000 years. These measurements are called ___.

Soundings

Just like river valleys on land, ___ are V-shaped and formed through the process of erosion. They are believed to be created when ocean levels fall and the continental slope becomes exposed.

Submarine canyons

A sounding is a measurement of ___.

The depth of the ocean

Two of the following sentences describe active margins and two describe passive margins. Choose the two active margin descriptions.

The transition from continent to ocean is also a move from one tectonic plate to another. The continental shelf is narrow.

Which of the following describe trenches?

They are the deepest places in the oceans. Some of them are associated with island arc systems.

What happened to continental shelves during the glacial ages of the Pleistocene epoch?

They were exposed as ocean levels fell. River valleys extended outward onto the shelves, as the water had a longer journey to the ocean.

What seafloor feature listed here would havea relatively low gravitational attraction resulting in a lower sea surface elevation above it?

Trench

Which of the following statements correctly describes the relationship between glacial ages, sea level, and continental shelves?

When glacial ages occur, water is tied up in glaciers, causing sea level to fall and more of the continental shelf to be exposed.

A continental shelf is ___ than the water is deep.

Wider