Earth Science Chapter 15

The flattest surfaces on Earth are ____.

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

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

an oceanic trench

The continental rise on a passive continental margin is a/an:

apron of terrigenous sediment that was transported across the continental shelf and deposited on the deep ocean floor at the foot of the continental slope

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

atoll

The Mid-Oceanic Ridge is composed mainly of:

basalt

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

chemosynthesis

Samples can be taken from the deep sea floor by:

coring devices

Oceanic crust is ____ than continental crust and therefore ____ isostatically.

denser, sinks

A magnetometer could be used to:

determine the orientation of the Earth's magnetic field at the time the mineral cooled

A/An ____ is a submarine mountain that rises 1 kilometer or more above the surrounding sea floor.

seamount

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 ____.

1 layer

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

The depth of the central parts of the ocean basins is about ____ kilometers.

5

Oceans cover about ____ percent of the Earth's surface.

71

Most of layer 3 of the oceanic crust is composed of ____.

gabbro

The Mid-Oceanic Ridge rises high above the surrounding sea floor because new lithosphere forming at the ridge axis is ____ and of relatively ____ density.

hot, low

Most of the water that fills the Earth's oceans came from:

interplanetary space

An oceanic island:

is a seamount that rises about sea level

Rift valleys are characterized by ____ faults and ____ earthquakes.

normal, shallow

Moving away from mid-ocean ridges, oceanic crust becomes:

older, sinks, and forms the abyssal plains

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

passive continental margin