Geo test 3 chap 15

The flattest surfaces on Earth are ____.

abyssal plains

California, Oregon, Washington, and western British Columbia were added to North America as ____________________ ____________________.

accreted terrane

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

The Mid-Oceanic Ridge is composed mainly 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

Continental margins on both sides of the Atlantic Ocean are ____________________ ____________________ ____________________.

passive continental margin

A/An ____________________ ____________________ is a deep trough in the crest of many mid-ocean ridges.

rift valley

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

seamount

A chain of volcanic islands that form along a subduction zone is called a/an ____________________ ____________________.

volcanic arc

An active continental margin forms:

where an oceanic plate sinks beneath a continental plate at 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

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

Gabbro

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

Oceans cover about ____ percent of the Earth's surface

71

A flat-topped seamount is called a/an ____________________.

guyot

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

Rift valleys are characterized by ____ faults and ____ earthquakes

normal, shallow

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

oceanic island

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