Chapter 15 – 20 Questions – Flashcards
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Oceanic crust is mostly composed of ____________________.
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basalt
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____________________ ____________________ 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.
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Pelagic sediment
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Beyond the Mid-Oceanic Ridge system are flat, level, featureless submarine surfaces called ____________________ ____________________.
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abyssal plains
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A circular coral reef that forms a ring of island around a central lagoon is a/an ____________________.
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atoll
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Oceanic crust is ____ than continental crust and therefore ____ isostatically
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denser, sinks
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The average thickness of oceanic crust is about ____, whereas the average thickness of continental crust is about ____.
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4-7 km, 20-40 km
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Sand, silt, and clay that erodes from the continents and is carried to the deep sea floor is called ____.
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terrigenous sediment
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The age of the oldest ocean floor is about ____ million years.
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200
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Island arcs grow from ____.
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submarine volcanoes near a subduction zone
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Submarine canyons on continental shelves and slopes are cut by ____.
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turbidity currents
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Remote sensing devices used to study the ocean floor are:
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magnetometers, echo sounders, and microwave radar instruments
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At sea-floor vents, bacteria produce energy from hydrogen sulfide in a process called:
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chemosynthesis.
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The part of oceanic crust made up of pelagic and terrigenous sediment is:
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layer 1
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If a series of island arcs collide with a continent over a long period of time, they add to a continent as:
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accreted terranes
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When two oceanic plates converge, the sinking plate drags the sea floor down to create:
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an oceanic trench
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Continental crust and oceanic crust firmly join together at a/an:
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passive continental margin.
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An active continental margin forms:
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where an oceanic plate sinks beneath a continental plate at a subduction zone.
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Some of the world's richest offshore petroleum reserves are found on continental shelves.
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True (some)
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A continental shelf on a passive margin is usually a wide bathymetric feature.
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True (a continental)
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At present, the Atlantic Ocean is growing, while the Pacific is shrinking.
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True (At present)
