Geo 103 Third Exam

Front 1

Sediment, typically with graded bedding, that is deposited by a turbidity current

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turbidite

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How do deep sea fans form?

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Turbidites abound at the mouth of submarine canyons, where they form thick sequences of cone-shaped deposits known as deep-sea fans.

Front 3

What carves out deep sea canyons, how?

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Excavated by a combination of sediment slumping and turbidity currents that have deepened a gully, or depression, on the sea bottom.

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Pelagic sediment containing >30% by volume shells of microorganisms

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ooze

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What organisms make up calcareous ooze?

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Zooplankton and phytoplankton

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What organisms make up siliceous ooze?

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Diatoms and radiolaria

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Inorganic deposit that consists of extremely fine-grained particles that typically have a brownish color

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pelagic red clay

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Why is it as hard to erode clays as it is to erode gravels?

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Part of the explanation lies in the fact that mud - a mixture of clay and silt - is more cohesive and, hence, "stickier" than sand, and so a stronger current is needed to dislodge a mud particle from the bottom than a fine grain of sand.

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Which sediment is the easiest to erode?

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sand

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Sediments on the continental shelves

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neritic sediment

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Hydrogenous sediment made up of 2 parts manganese dioxide and 1 part iron oxide

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manganese nodules

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What is the Manganese Nodule Mystery?

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How come the Mn nodules are mostly exposed and there are about the same density of nodules in every layer of sediment?

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Small spheres deposited in high wave activity, as the rolling by waves makes them round as the calcium carbonate is deposited a little at a time

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ooids

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the region of a subduction zone located between the deep-sea trench and volcanic arc, where thick sedimentary units and volcanic rocks are squeezed and wrinkled by compression to form thrust faults and tight holds

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accretionary prism

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Develop along the edges of continents that are located far from the tectonic effects of plate boundaries and have a long history of passive sedimentation

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Atlantic-type margin

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Deposits consisting of >30% by volume of particles produced by organisms, such as shells of diatoms, radiolaria, and foraminifera

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biogenous sediment

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Gravity-induced transport of sediment, such as slumping and turbidity currents

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bulk emplacement

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composed of calcium carbonate

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calcareous ooze

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The depth in the ocean below which material composed of calcium carbonate is dissolved and does not accumulate on the seafloor

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carbonate compensation depth

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Microscopic, unicellular phytoplankton possessing silica valves; they are responsible for much of the ocean's primary production

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diatoms

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Chemically precipitated from seawater, these more-or-less spherical masses, a few millimeters to several centimeters in diameter, are composed of concentric layers of iron, manganese, and other metal oxides

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ferromanganese nodule

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Planktonic and benthonic protozoans that have a test composed of calcium carbonate

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foraminifera

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Vertical grain-size gradation in a layer of sediment, typically with the coarsest particles at the bottom of the bed, the finest at the top

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graded bedding

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particles that are precipitated by chemical or biochemical reactions in seawater near the sea floor; manganese and phosphate nodules are examples

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hydrogenous sediment

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An opening in the ground from which pour out hot, saline water solutions

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hydrothermal vents

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The transport of sediment to the deep sea by floating icebergs which melt and drop their sediment load

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ice rafting

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A sedimentary rock composed dominantly of calcium carbonate, either precipitated from seawater or deposited as shell debris

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limestone

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Dominated by a subduction zone and are built up of highly deformed sedimentary beds that may be interlayered with lavas and volcanogenous sediment

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Pacific-type margin

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The inorganic deposit that contains extremely fine-grained particles that typically have a brownish color

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pelagic clay

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Deep-sea sediment that accumulates on the seafloor by the slow settlement of grains through the water column

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pelagic sediment

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A hydrogenous deposit consisting of nodules or crusts of P2O5

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phosphorite

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Microscopic, unicellular planktonic and benthic animals that possess siliceous tests

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radiolaria

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Sand sediments that are buried, the grains are compacted, cemented, and slowly transformed into sedimentary rock

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sandstone

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Mud sediment that is buried, the grains are compacted, cemented, and slowly transformed into sedimentary rock

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shale

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Material whose composition is silica

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siliceous ooze

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The sliding of large, cohering blocks of sediment or rock downslope under the influence of gravity

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slumping

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The branch of geology that studies the relationship and significance of layered sedimentary rocks

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stratigraphy

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Sediments derived from the mechanical weathering of rocks on land

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terrigenous sediment

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Poorly sorted sediment that is deposited by glaciers

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till

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Sediment, typically with graded bedding, that is deposited by a turbidity current

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turbidite

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A density-driven slurry of sediment-laden water which flows swiftly downhill displacing less dense water

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turbidity current

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Sediment derived from volcanoes

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volcanogenous sediment

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A tilted zone of earthquakes associated with collisional plate boundaries known as subduction zones

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Benioff zone

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A force that pushes together parts of a rock or structure, decreasing its volume

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compressional stress

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The process whereby continents are and have been in motion relative to one another across the Earth's surface

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continental drift

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Plates that extend downward through the brittle outer shell of the Earth that includes the crust and uppermost mantle

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lithospheric plate

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The relatively cool, brittle, outer shell of the earth, some 100 kilometers thick, that includes the crust and uppermost mantle

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lithosphere

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Long, linear bands of basalt crust that lie parallel to a spreading ocean ridge and that are alternately normally and reversely magnetized

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magnetic anomaly stripe

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The upwelling of hot material into and through the lithosphere, with magma spilling out onto the Earth's surface and building thick volcanic piles

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mantle plume

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Oriented as it is at present

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normal polarity

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This "fossil" magnetization is quite stable over geologic time, particularly in basalts, and provides a clear magnetic record unless the rock has been reheated or deformed

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paleomagnetism

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The study of fossils

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paleontology

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The megacontinent of the Mesozoic Era that consisted of all of the present-day continents joined together into a single unit

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Pangaea

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The theory that the Earth's lithosphere is divided into broad, irregular plates that are either converging, diverging, or slipping by one another

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plate tectonics

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Oriented in the opposite direction

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reverse polarity

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The fault-bounded valley found along the crest of many ocean ridges; it is created by tensional stresses that accompany the process of sea-floor spreading

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rift valley

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The process by which basaltic crust is created at the crest of ocean ridges where lithospheric plates are diverging

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sea-floor spreading

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The distribution, frequency, and magnitude of earthquakes in an area

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seismicity

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A high-angle fault, such as a transform fault, along which rocks move horizontally

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strike-slip fault

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A collisional plate boundary along which one lithospheric overrides another and produces a deep-sea trench, a volcanic arc, and seismicity

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subduction zone

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Term that denotes deformation of the crust

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tectonism

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"pull-apart" force

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tension

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heat transfer by fluid motion

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thermal convection

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A steep boundary separating two lithospheric plates along which there is lateral slippage

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transform fault