CHAPTER 9

groin

barriers build perpendicular to the shore -made to capture sand from the longshore drift to stop beach erosion or rebuild a beach

Why don't submarines experience severe storms at sea?(hint: think about "wave base")

because they are in the wave base. this is where the wave motion dies out. therefore they can not feel anything

fetch

distance over which wind blows

What effect do sea walls have on the sandy beach next to them?

they can increase the erosion of the beach fronting the seawall

breakwater

-barriers built parallel to the coast in water -used to protect harbors -barrier makes waves break offshore, reducing energy expended to the shore

seawall

-big structures built parallel to the coast designed to withstand the full force of storm waves -ex: curved seawall on the south shore of Galveston, Texas

jetty

-can cause sediment to be carried away from the shore into deeper water -extend out from the shore -creates negative sediment budget on the shore and depletes sediment supply

tide

-daily flactuating rise and fall of sea level -fluctuates btwn two high and two low tides a day -caused by gravitational interactions among earth moon and sun

wave length

-horizontal distance between to successive crests

barrier island

-long, low lying ridges of sand and gravel and sand isolated from the mainland by shallow lagoons and bays -an ex is Assateague Island, Maryland

longshore drift (littoral drift)

-movement of sediment by longshore currents

dredging

-people remove unwanted sediment by doing this -scooping sediment off the bottom away from the suction dredges

wave refraction

-the bending of a wavefront because one end of the wavefront is slowing down relative to the rest of it

wave base

-the depth at which the wave motion dies out -determined by the wave length of the waves -depth of this is 1/2 wave length

longshore current

-waves breaking offshore at an angle that cause water the move along the shore -transport sediment along the coast

eustatic sea level change

World-wide sea level change. (As opposed to local changes due to land being uplifted or down- dropped due to movements on faults, for example.)

What shoreline structures are built to impede longshore drift? What is the pattern of sand deposition and erosion around them?

a longshore drift is the movement of sediment by currents... so groin and jetty are built to impede these. -groin: captures sand from the lonshore drift to stop erosion -jetty: makes sediment get carried away from the shore into deeper water -the pattern is that they both capture the sand decompostion and place it else where to stop erosion

What creates ocean waves?

local winds or winds in distant storms

How do longshore currents develop, and how do they impact beaches and swimmers?

longshore currents develop from waves breaking offshore at an angle. these impact beaches bc they transport sediments along the coast. these impact swimmers because they push you farther down the beach away from your original spot.