costal processes Flashcards
1
Q
How do waves form?
A
- water molecules have circular orbits below waves
- orbits become smaller with depth
- as waves appraoch the shore, orbits become ellipitical and develop into breakers
2
Q
why do we need to understand coastal processes
A
- much of the worlds population lives on or close to coasts
- approx 3 billion live within 100km of a coast
- twenty one of the worlds 33 megacities
- canada has largest coastline in the world (over 200,000km)
- sea is rising due to global warming
- we need to carefully plan coastal land use
- potential displacement of approx 1 billionpople
- sea level is rising 3.3mm per year
- ex. venice
3
Q
what is a mega city
A
- a city with over 10 million people
4
Q
what is wave base
A
- depth at whic water movement is negligable
- where thi wave breaks
- this is important because it tells us the size of wave we need to prep for and for erosion and for surfing/boating
5
Q
what is longshore drift
A
- sediment moving parallel to coastline
- occurs when waves appraoch coast at an oblique angle
- the sediment moves obliquley up the beach by swash
- mves directly downslope in backwash
- transports sediment along coast
- maintain supply of sediment to bech
- forms spits and bars
- ex. of spit. Farewell spit, New Zealand
- groins used to trap sediment and widen beach but this can cause erosion downstream
6
Q
spits
A
- ridges of sediment that extend into open water
7
Q
bars
A
- ridges of sediment that cut off bays from open water
8
Q
coastal structures
A
- groins
- jetties which may cause deposition and erosion of sand. it stops longshore drift and creates a passage
- breakwaters which strong wave action and protect areas of the shore from waves; sand can be deposited in protected area
9
Q
rip currents
A
- narrow currents that flow out to sea (returning the water seaward)
- travel at water surface
- transport sediment
- important to swimmera
10
Q
shoreline environments
A
- shoreface- below low tide mark. sediment gets sandier towards shore
- beach face- steepest part of the beach, lots of wave action
- backsore/dune- landwars or beach, sand blown inland forms dunes
11
Q
backshore dune system
A
- along the coast of lake erie
- “the sand hills”, port burwell
- over 75km high
- created from last glacial age
12
Q
how to beaches develop
A
- beaches usually composed of sand:
shell fragments in tropical area, gravel in colder areas - seasonal cycle:
storm waves in winter erode beach face and build offshore sand bar. low energy waves in summer move sand onshore
13
Q
canadian beaches
A
- often affected by ice
- top of water freezes over
- wind puches ice mounds to shoreloine
- lake of sea ice blown onshore in winter
- boulders can be moved onshore to form boudler barricades or ramparts
- boulder barricades are elongae rows of boudlers that flank the coastline, separated from the shore by an intertidall flat
- result of ice transport
- only in arctic and sub arctic regions
14
Q
what are tides
A
- sea level on earths surface rises and falls one or twice daily as tide
- caused by tide generating forc created by gravitational attraction of moon and sun
- creates two bulges in oceans: one closest to the moon and the other on the opposite side of Earth
- as earth rotates: water levels rise (flood tide) and water levels fall (ebb tide)
- tidal range is the difference in sea level between high and low tides
15
Q
bay of fundy
A
- highest tidal range in the wold
- increases toward coats
- between nova scotia and new brunswick
- tidal range greater than 16m
- tidal bore can reach speeds of 35km/h
