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Beaches and Shores
Beaches and Shores Exam 2 (ch.5,6,7,8,9)
Question | Answer |
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isobars | line connecting points of equal barometric pressure on a weather map |
Coriolis effect | .apparent deflection of moving particles on rotating earth. in the northern hemisphere moving particles are deflectedtot he right, whereas in the southern hemisphere they are deflected to theleft. there is no apparent defection at the equator |
horse latitudes | high-pressure region occurring at 30 degrees latitude. formed by a descending airmass that compresses, producing high pressure, dry air, and variable winds. so naed due to early sailing ships being becalmed in these latitudes and throwing out horses |
Ferrel cell | atmospheric convection cell existing between 30 and 60 latitude. this cell is formed due t sinking air at 30 degrees latitude and rising air at 60 degrees latitude |
polar cell | weak circlation cell that occurs between 60 and 90 degrees latitude. it results from upper air masses movement northward and descending at the poles, while at the same time surface air flow south |
easterlies | planetary-scale surface winds that blow from the northeast in the tropics. aka "trace winds" |
intertropical convergence zone (ITCZ) | zone of converging northeast trade winds and southeast trade winds. this zone occurs at about 5 degrees north of the equator |
westerlies | a belt of prevailing winds in the mid-latitudes (30-60 degrees) that flow from west to east |
polar easterlies | part of the global air circulation pattern where winds blow from the polar high toward the subpolar low |
polar front | at about 50-60 degrees latitude the polar easterlies meetthe westerlies, establishing the polar front. this convergent zone produces a near permanent boundry separating the cold dense polar air from the warm tropical air mass |
anticyclones | dome of high pressure air producing a clockwise-circulating air mass |
sea breeze | breeze that blows onshor due to the warming of the landmass during the day |
land breeze | breeze that blows offshore due to the cooling of the landmass during the evening and night |
cyclogenesis | process of cyclone development (low pressure system). cyclonic circulation is formed along an advancing frontal system in which the two air masses have a slight component of differential movement |
northeasters | type of extratropical cyclone that travels northward along the east coast of the US and Canada, producing strong winds and waves from the northeast |
berm | that flat upper surfaces of the steplike features that may occupy the backshore |
law of conservation of momentum | product of an object's velocity around its center and in its distance from the center squared is constant |
capillary waves | the first wave to develop when the wind begins to blow over a water surface. the wavelength is less than 1.7 cm and the restoring force is primarily surface tension |
gravity waves | waves whose velocity of propagation is controlled primarily by gravity. most wind-generated waves are gravity waves |
wavelength | (L) the horizontal distance between successive wave crests |
wave height | (H) the vertical difference between the wave crest and the adjacent trough |
period | (T) time in seconds that it takes for a complete wavelength to pass a reference point |
celerity | (C) velocity that a wave propagates across the water surface. C=L/T |
significant wave height | the average height of the highest one-third of waves in a given area |
setup | a rise in water elevation above still water in the surf zone due to breaking waves piling up water |
wave base | the depth to which sediment is distrubed by surface waves. this depth is usually defined as equal to hald the wavelength |
surf zone | the zone landward of the breaker zone where breaking waves create a turbulent flow of water toward the beach |
sea waves | waves formed at the generated site under the influence of local winds |
swell wave | waves that have moved away from the generation zone and have similar periods, lengths, and heights. these are the waves that break along a beach when the wind isn't blowing |
plunging breakers | curled-shaped breaking wave that break all at once. the classic wave for surfers due to the elliptical-shaped pocket of air beneath the crest |
spilling breakers | a type of breaking wave in which the crest peaks and then water cascades down the front of he wave. this wave continues to break along a wide section of the nearshore zone |
refraction | bending of the wave as it passes through shallow water on its way to the shoreline |
diffracted | occurs as waves pass an impermeable obstacle such as a jetty, breakwater, or other type of structure that causes the wave energy to spread along the crest behind the obstacle |
reflection | angle of reflection is equal to angle of incidence |
tsunami | a long-period, high-velocity wave produced by a disturbance of the sea floor, volcanic eruption, or meteor impact |
standing waves | a wave in which the water surface oscillates vertically between fixed points where there is no movement. they commonly occur in a bay or a semi-enclosed coastal body of water |
seiche | a standing wave in a coastal or semi-enclosed body of water. the wave sloshes back and forth with a period of minutes to hours |
longshore current | current in the nearshore zone that is produced by angular wave approach |
littoral transport | annual amount in a particular length of coast. (eg. 100,000 m^3yr^-1 from north to south) |
littoral drift | sediment that hasbeen trasported in the nearshore zone by the longshore current. it is the material that has been moved, not the process of movement. the term describing the process is called longshore sediment transport |
rip currents | seaward-directed current that flows through the breaker zone, almost perpendicular to the beach, and quickly dissipates. the current is fed by the longshore current and may reach veolcities up to several kilometers per hour |
undertow | water from the swash zone returning seaward at the bottom of the water column |
nearshore environment | adjacent, shallow marine waters. incldes the region that extends from the low tide line, which is the seaward extent of the beach, out across the surf zone, nd includes the sand bars that are common along most coasts |
longshore bars | shore-parallel sand bar in the nearshore zone that is formed by wave processes |
ridge and runnel | inshore bar that migrates onshore and repairs a beachfollowing storm-induced erosion. commonly they are less than 1 m in height and are fronted by a steep face (slipface) along their landward margin |
foreshore | the intertidal portion of the beach, extending to te landward change in slope. aka the forebeach or beach face. includes the swash zone, the part of the foreshore over which the waves uprush and backwash as each one meets the shore |
backshore | landward portion of the beach, extending from the high-water line to the base of the dunes or cliff face. this region of the beach is covered by water only during storms and exceptionally high spring tdes. aka backbeach |
berm | the flat upper surfaces of the steplike features that may occupy the backshore |
dissipative beaches | beach with a flat to low gradient profile such that wave energy is expended over a wide area |
reflective beaches | beach cntaining a relatively steep beachface on which little of the wave energy is dissipated before it breaks on the beachface |
accretionary beach | a beach where the dominant condidtion is deposition of sediment or stability; erosion is absent or quite limited |
storm beach | a flat featureless beach that is produced by storm erosion |
heavy minerals | minerals with a specific gravity greater than 2.85. they include garnet, ilmenite, magnetite, sphene, and zircon |
sand | grains with a size range between 0.0624 and 2.0 mm |
beach | deposit of unconsolidated sediment, ranging from boulders to sand, formed by wave and wind processes along the coast. the beach extends from the base of the dunes, cliff face, or change in physiography seaward to the low-tide line |
barrier interior | middle of the barrier extending landward from the foredune ridge through the secondary dune system to the rear of the barrier. this region commonlt consists of one or more of these elements: isolated dunes, sand sheets, washovers, blowouts, ridge, etc. |
landward margin | the back side of a barrier, which might abut an intertidal sand or mud flat, a salt marsh, or an open water area assocatiated with a lagoon, bay, or tidal creek |
amero-trailing edge coast | coast defining the passive margin of a continent in which the opposite sie of the continent is a collision margin (east coast of N&S America). typically low-lying and depositional, and receives large quantities of sediment |
marginal sea coasts | continental coastline landward of an island-arc system |
collision coasts | coastline coinciding with the convergence of two lithospheric plates (eg. west coast of N&S America) |
Afro-trailing coasts | coast defining the passive margin of a continent in which the opposite side of the continent is also a passive margin (eg. east and west coasts of Africa). the lack of a collision zone means that there are nomajor mountain systems to put sediment to coast |
Neo-trailing edge | coastlines along linear seas that have been created by spreading zones. these coass are geologically young, such as the red sea |
recurved spits | hook-shaped spit that builds into bay or along the cost through the addition of curved beaach ridges |
cuspate spits | triangular accumulation of sand that extends from a barrier or mainland shoreline into a bay or lagoon. characterized by converging sand transport cells |
flying spits | type of spit that occurs along straight to sligtly irregular shorelines and extends at an acute angle to the beach. theyre found along semi-protected shrelines and may contain recurved ridges |
tombolos | intertidal or supratidal accumulation of sediment connecting the bach to an island. the sediment builds from the beach toward the island due to wave sheltering and convergence of longshore currents |
cuspate forelands | a broader tiangular projection of the shoreline commonly referred to as a cape. it may be more than 25km across and associatedwith converging longshore transport systems and/or formr river deltas |
offshore bar theory | de Beaumont believed that waves movng into shallow water churned up san, which was deposited in the form of a submarine bar when the waves broke and lost much of their energy |
spit accretion theory | Gilbert argued that the barrier sediments came from alongshore sources |
submergence theory | McGee believed east and gulf coasts of the US were undergoing submergence |
prograding barriers | types of barrier that builds seaward during its evolution due to an abundant sediment supply |
beach ridges | vegetated former foredune ridges marking previous beach positions. low areas between ridges are called swales |
scarp | steep erosional face of a sedimentary deposit, such as the dune scarp that is formed during storm induced erosion of the foredune |
wrack lines | a debris line found along the upper shore marking the greatest excursion of the wave up the beachface or berm during the previous spring high tide or storm high tide. consists of seaweed, eelgrass, marsh grass, or driftwood |
bar migration | the landward movement of a subtidal or intertidal sandbar toward the shoreline. the onshore migration is due to the action of breaking and shoaling waves as well as wave-generated currents. on ebb-tidal delas, flood-tidal currents, etc. |
retrograding barriers | topographically low barrie that migrates onshore primarily through overwash activity during storms. barrier sands are underlain by marsh, lagoonal, nad mainland sediments |
barrier rollover | the landward migration ofa barrier, accomplished primarily through the process of storm overwash |
overwash | sediment that is transported from the beach across a barrier, and is deposited in an apron-like accumulation along the backside of the barrier. overwash usually occurs during storms when waves brak through the frontal dune ridge and flow toward the marsh |
aggrading barrier | barriers that build vertically in a regime o rising sea leveland generate the same approximate arrangement of environments as they did following their formation and stabilization |
stratigraphy | the study of the composition and relationship of layered sediments or rocks |
prograding barrier | type of barrier that builds seaward during its evolution due to an abundant sediment supply |
retrograding barrier | topographically low barrier that migrates onshore primarly through overwash activity during storms. barrier sands are underlain by marsh, lagoonal, and mainland sediments |
aggrading barrier | barriers that build vertically in a regime of rising sea level and generate the same approximate arrangement of environments as they did following their formation and stabilzation |
foredunes | vegetated coastal dune system that forms the landward borer to the beach. aka foredune ridge or primary dune |
sand shadows | small accumulation of sand that is deposited in the sheltered area behin an obstruction, such as a rock, shell, or piece of debris |
coppice mounds | small accumulation of wind-blown sand around a plant |
blowover | the most common process for dune migration |