Exam 3 Flashcards by Maddy VanHandel

Invented in 1920s
Primary instrument for measuring depth
Reflects sound from ocean floor

Echo Sounder

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Employs an array of sound sources and listening devices
Obtainsa profile or a narrow strip of seafloor

Multibeam Sonar

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Found along most coastal areas that surround the atlantic ocean
Not associated with plate boundaries
Experience little volcanism and free earthquakes

Passive Continental Margin

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Flooded extension of the continent
Varies greatly in width
Gently sloping
Contains important mineral deposits
Some areas are mantle by extensive glacial deposits

Continental Shelf

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Marks the seaward edge of the continental shelf
Relatively steep structure
Boundary between continental crust and oceanic crust

Continental Slope

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Found in regions where tranches are absent
Continental slop merges into a more gradual incline - the continental rise
Think accumulation of sediment
At the base of the continental slope turbidity currents deposit sediment that forms deep-sea fans

Continental rise

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Primarily in pacific
Trench
Accretionary wedge

Active Margins

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Long, relatively narrow features
Deepest parts of the ocean
Most are located in the pacific ocean
Sites where moving lithospheric plates plunge into the mantle
Associated with volcanic activity

Deep Ocean Trench

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Likely the most level places on Earth
Sites of thick accumulations of sediment
Found in all oceans, especially atlantic

Abyssal Plains

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Isolated volcanic peaks
Many form near oceanic ridges
May emerge as an island

Seamounts

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Vast outpourings of basaltic lavas on the ocean floor create extensive volcanic structures

Oceanic Plateaus

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Broad, linear, swells along divergent plate boundaries

Oceanic ridges

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Axis of some ridge segments exhibit deep down-faulted structures

Rift Valleys

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Concept formulated in early 1960s by Harry Hess
Occurs on relatively narrow zones, called rift zones, located at the crest of ocean ridges

Seafloor spreading

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Newly created oceanic lithosphere is hot and occupies more volume than cooler rocks
As the basaltic crust travels away from the ridge crest it is cooled by seawater
As the lithosphere moves away it thermally contracts and becomes more dense

Why are oceanic ridges elevated

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sequence of unconsolidated sediments

Layer 1 of oceanic crust

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consisting of pillow lavas (basalt)

Layer 2 of oceanic crust

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numerous interconnected dikes called sheet dikes (basalt)

Layer 3 of oceanic crust

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gabbro, in a sequence of rocks called an ophiolite complex

Layer 4 of oceanic crust

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Basaltic magma originates from partially melted mantle peridotite
Molten rock injected into fractures above the magma chambers creates the sheeted dike complex
The submarine lava flows chill quickly and the congealed margin is forced upward to provide large tube-shaped protuberances known as pillow basalts

Formation of oceanic crust

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Hydrothermal fluids dissolve ions of various metals and precipitate them on the ocean floor as particle filled clouds

Black smokers

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Mantle plumes/ hotspots
Slab pull/slab suction

Two mechanisms that have been proposed

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Concept of floating crust in gravitational balance
If weight is added or removed from the crust, isostatic adjustment will take place as the crust subsides or rebounds

the principle of isostasy

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Buoyancy of hot rising mantle material accounts for broad upwarping in the overlying lithosphere

vertical motions and mantle convection

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the processes that collectively produce a mountain belt Including folding, thrust faulting, metamorphism, and igneous activity

Orogenesis

region where subduction g oceanic lithosphere bends and descends into the asthenosphere

Deep ocean trench

built upon overlying plate Island arc if on ocean floor or Continental arc if oceanic lithosphere is subducted beneath a continental block

volcanic arc

As the subducting plate sinks in creates a flow in the asthenosphere that pulls the upper plate toward the trench

Extension and back arc spreading

Where two oceanic plates converge and one is subducted beneath the other Volcanic island arcs result from the steady subduction of oceanic lithosphere Continued development can result in the formation of mountainous topography consisting of igneous and metamorphic rocks

Island arc mountain building

Mountain building along continental margins Involves the convergence of oceanic plate and a plate whose leading edge contains continental crust Andes mountains

Andean arc mountain building

Subduction and particle melting of mantle rock generates primary magmas Magma is less dense than surrounding rock so it begins to buoyantly rise Differentiation of magma produces andesitic volcanism dominated by pyroclastics and lavas

Building a volcanic arc

An accretionary wedge is a chaotic accumulation of deformed and thrust-faulted sediments and scraps of oceanic crust Prolonged subduction may thicken an accretionary wedge enough so it protrudes above sea level Descending sediments are metamorphosed into a suite of high-pressure, low-temperature minerals

Development of an accretionary wedge

The growing accretionary wedge acts as a barrier to sediment movement from the arc to the trench This region of relatively undeformed layers of sediment and sedimentary rock is called forearc basin

Forearc basin

a summary of the circulation of Earth’s water supply

hydrologic cycle

Begins as sheetflow Infiltration capacity is controlled by Intensity and duration of rainfall Prior wetted condition of the soil Soil texture Slope of the land Nature of the vegetative state

Running water

Sheetflow develops into tiny channels

Rills

Gradient, or slope Channel characteristics including shape, size, and roughness Discharge - the volume of water moving part a given point in a certain amount of time

Factors that determine velocity

Laminar flow

slower flow

turbulent flow

faster flow

Cross-sectional view of a stream Viewed from the head (headwaters or source) to the mouth of a stream A smooth curve Gradient decreases downstream

profile

Velocity Discharge Chanel size

increase downstream

Gradient Channel roughness

decrease downstream

Lifting loosely consolidated particles by Abrasion Dissolution Stronger currents lift particles and move them more effectively

stream erosion

the stream’s load Types of load Dissolved load Suspended load Bed load

transported material

the maximum load a stream can transport

capacity

Indicates the maximum particle size the stream can transport Determined by the stream's velocity

competence

Competence is reduced Sediment begins to drop out

decrease in velocity

Generally well-sorted Stream sediments are known as alluvium

stream sediments

Back swamps Yazoo tributaries

floodplain deposits

Develops where high-gradient stream leaves a narrow valley Slopes outward in a board arc

alluvial fans

Form when a stream enters an ocean or lake Consist of three types of beds Foreset beds Topset beds Bottomset beds

deltas

V-shaped Downcutting toward base level Features often include rapids and waterfalls

narrow valleys

Steam in a ner base level Downward erosion is less dominant Stream energy is directed from side to side forming a floodplain

wide valleys

a this mass of ice that originates on land from the accumulation, compaction, and recrystallization of snow

glacier

Exist in mountainous areas Flow down a valley from an accumulation center at its head

valley glaciers

Exist on much larger scale than valley glaciers Two major ice sheets on earth (greenland and antarctica)

ice sheets

Air infiltrates snow Snowflakes become smaller, thicker, and more spherical Air is forced out Snow is recrystallized into a much denser mass of small grains called firn Ocne the thickness if the ice and snow exceeds 50 meters, firn fuses into a solid mass of interlocking ice crystals

formation of glacial ice

Occurs within the ice Under pressure, ice behaves as a plastic material

plastic flow

Entire ice mass slipping along the ground Most glaciers are thought to move this way

Basal slip

the area where a glacier forms Elevation of the snowline varies greatly

zone of accumulation

the area where there is a net loss to the glacier due to Melting Calving - the breaking off of large pieces of ice (icebergs where the glacier has reached the sea)

zone of ablation

lifting of rocks

plucking

Rocks within the ice acting like sandpaper to smooth and polish the surface below

abrasion

Rock flour (pulverized rock) Glacial striations (grooves in the bedrock) Landforms Glacial trough Arêtes Horns Hanging valleys Cirques Fjords Truncated spurs

glacial abrasion products

refers to all sediments of glacial origin Types of glacial drift Till - material that is deposited directly by the ice Stratified drift - sediments laid down by glacial meltwater

glacial drift

Smooth, elongated, parallel hills Steep side faces the direction from which the ice advanced Occur in clusters called drumlin fields Formation not fully understood

drumlins

line that marks the contact between land and sea - moves during the day with tides

shoreline

extends between the lowest tide level and the highest elevation affected by storm waves

shore

area exposed at low tide and submerged at high tide

foreshore

area found landward of the high-tide mark

backshore

lies between the low-tide shoreline and the point where waves break at low tide

nearshore zone

seaward of the nearshore zone

offshore zone

an accumulation of sediment found along the landward margin of an ocean or lake

the beach

extends inland from the shore as far as ocean-related features are found

coast

marks the coast’s seaward edge

coastline

he horizontal distance between two crests Below a depth of ½ wavelength, water movement is no longer felt If you are scuba diving in the ocean, you will not feel the effects of a storm passing the surface

wavelength

turbulent water that washes up a beach Greater on flat beaches at an angle

swash

is water flowing back into the ocean after swash straight down

backwash

Currents parallel to shoreline produced in surf zone by waves reaching shore at an angle

longshore current

Wave cut cliffs Wave cut platform Marine terraces (old wave cut platforms elevated by changing sea level or local uplift) Sea arches Sea stacks

erosional coast features

Composed of sediment that is eroded, transported, and deposited by wave energy

depositional coasts

an elongated ridge of sand that projects into the mouth of an adjacent bay

spit

a sandbar that crosses a bay, cutting it off, from open ocean

bar

Low ridges of land parallel to the coast Gebrally 3-30 km offshore 1-5 km wide, 15-30 km long

barrier islands

built perpendicular to the shoreline and extend into the ocean near the mouths of rivers and harbors Usually built in pairs to develop and maintain harbors Results in deposition and up-current and erosion down-current

jetties

Built perpendicular to the beach and extend into the ocean Designed to maintain or widen beaches: causes erosion downstream

groins

Creates a region of sand accumulation between the breakwater and the shoreline Built offshore to protect property from breaking waves Causes deposition landward of breakwater

breakwater

Built onshore to protect property from breaking waves Focuses wave energy at seawall, increases backwash Causes severe erosion seaward of seawall

seawall

Adding large quantities of sand to the beach Costly and not a permanent solution

nourishment

Develop because of uplift of an area or a drop in sea level Generally erosional

emergent coasts

Caused by subsidence of land adjacent to the sea or a rise in sea level Usually depositional Features: Estuaries (drowned river mouths) Highly irregular shorelines

submergent coasts

Atmosphere Hydrosphere Geosphere Biosphere Cryosphere (ice and snow)

the climate system

Plates tectonics (very long term) Variations in Earth orbit (long term) Eccentricity, obliquity, and precision Volcanic activity (short term) Changes in the sun’s output associated with sunspots

natural causes of climate change

Humans have been modifying the environment for thousands of years as ground cover has been altered by Fire Overgrazing Modification of climatological factors such as reflectivity, evaporation rates, and surface winds (windmills for power)

anthropogenic climate change

Because the climate system is so complex, predicting specific regional changes to increased levels of CO2 is speculative However, some possible consequences include Rise in acidic as well as sea level (virtually certain) Altering the distribution of the world’s water resources (very likely) Changes in the extent of Arctic sea ice and permafrost (very likely) Frequency of heavy precipitation (very likely) Areas affected by drought (likely) Loss of glaciers will accelerate (likely) Greater intensity of tropical cyclones (not sure)

consequences of global warming

Changes that reinforce the initial change are called positive-feedback mechanisms Warmer surface temperatures cause an increase in evaporation, increases temperatures as water vapor absorbs more radiation, warmer surface temperatures Warm ocean. Longer melting, decline in ice, reduced reflectivity (albedo), increased absorption of solar energy, warm ocean…

climate feedback mechanisms

Produce results that are opposite of the initial change and tend to offset it Example - negative effect of increased cloud cover, ash, and haze on the amount of solar energy available to heat the atmosphere

negative feedback mechanisms

Exam 3 Flashcards

(97 cards)