Chapter 15 - 20 Questions

____________________ ____________________ is a mixture of clay carried from continents and the remains of tiny plants and animals that live in the surface waters of the oceans.

Pelagic sediment

At present, the Atlantic Ocean is growing, while the Pacific is shrinking.

True (At present)

A continental shelf on a passive margin is usually a wide bathymetric feature.

True (a continental)

Some of the world's richest offshore petroleum reserves are found on continental shelves.

True (some)

Beyond the Mid-Oceanic Ridge system are flat, level, featureless submarine surfaces called ____________________ ____________________.

abyssal plains

If a series of island arcs collide with a continent over a long period of time, they add to a continent as:

accreted terranes

When two oceanic plates converge, the sinking plate drags the sea floor down to create:

an oceanic trench

A circular coral reef that forms a ring of island around a central lagoon is a/an ____________________.

atoll

Oceanic crust is mostly composed of ____________________.

basalt

At sea-floor vents, bacteria produce energy from hydrogen sulfide in a process called:

chemosynthesis.

Oceanic crust is ____ than continental crust and therefore ____ isostatically

denser, sinks

Remote sensing devices used to study the ocean floor are:

magnetometers, echo sounders, and microwave radar instruments

Continental crust and oceanic crust firmly join together at a/an:

passive continental margin.

Submarine canyons on continental shelves and slopes are cut by ____.

turbidity currents

An active continental margin forms:

where an oceanic plate sinks beneath a continental plate at a subduction zone.

Island arcs grow from ____.

submarine volcanoes near a subduction zone

Sand, silt, and clay that erodes from the continents and is carried to the deep sea floor is called ____.

terrigenous sediment

The part of oceanic crust made up of pelagic and terrigenous sediment is:

layer 1

The age of the oldest ocean floor is about ____ million years.

200

The average thickness of oceanic crust is about ____, whereas the average thickness of continental crust is about ____.

4-7 km, 20-40 km