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