GEO-200-Chapter 15

_______ _____ 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

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

True

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

True

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

True

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

Remote sensing devices used to study the ocean floor are:

all of these: - magnetometers - echo sounders - microwave radar instruments

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

an ocean trench

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

atoll

Ocean crust is mostly composed of ______.

basalt

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

chemosynthesis

Ocean crust is ___ than continental crust and therefore ____ isostatically.

denser, sinks

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

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

passive continental margin