What is a rip current? BONUS points if you can also explain how to escape one.
A rip current is a concentrated return current that moves quickly out to sea.
To escape, swim parallel to the shore!
100
Where do waves converge? Diverge?
Converge on headlands, diverge in embayments.
100
What scale do we use to measure wind strength?
The Beaufort Scale, 0-12.
200
What is wavelength?
The distance of one full cycle (crest to crest or trough to trough)
200
How does water move when a wave passes? Is there net movement?
Back and up, then down and forward, in a circular orbit. There is no net movement.
200
What is a rogue wave?
A wave that is 3 to 4 times larger than the other waves in the same area, product of constructive interference.
200
Under what two circumstances will a wave break?
1) When steepness exceeds a certain point (H/L = 1/7), the wave will collapse.
2) When depth is too great for height (H/D = 3/4), the base of a wave will be restricted by the sea floor and the crest will collapse forward.
200
What effect do waves have on seawalls?
Waves erode seawalls, and eventually they collapse.
300
What is wave celerity?
Speed! Distance per period
300
What is the difference between constructive and destructive interference?
With constructive interference, the crests and troughs of waves within packets line up. This creates bigger waves.
With destructive interference, crests and troughs mismatch and create smaller, lower energy waves.
300
The 3 generating forces for waves are gravity, earthquakes/slides/volcanoes, and wind. Which produces waves with the largest wavelength?
Gravity produces the tides, which have 10,000 km wavelength.
300
When do spilling and plunging breakers occur?
Spilling breakers occur on gradual shore slopes, while plunging breakers occur on steep shore slopes.
300
Where are jetties placed and why?
At inlets; their purpose is to keep inlets where they are.
400
What is a wave's amplitude?
1/2 its height
400
For deep water waves, speed is expressed as ______. For shallow water waves, speed depends on ______.
Wavelength / time. Gravity & depth
400
What does a restoring force do? State the two types.
Returns water to its undisturbed state. Surface tension and gravity
400
What is longshore drift? Why does it happen?
The transport of sediment along a shoreline in the direction of the current. Waves approach at an angle, so shore particles move straight back with a wave and hit at an angle again up the beach.
400
What is the purpose of a groin?
To trap sediments where they are and cause erosion/deposition in new areas.
500
What is the difference between wave period and wave frequency?
Wave period is seconds per cycle, wave frequency is cycles per second
500
What happens to a wave as it moves into shallower water?
Explain in terms of 1) speed, 2) height, 3) steepness, 4) period, and 5) orbitals.
It slows down, height increases, period STAYS THE SAME, and orbitals flatten.
500
What 3 factors affect the growth of wind waves?
Wind speed, wind duration, and fetch (length of water over which wind has blown)
500
Name three factors that shape the coastline.
Erosion, sediment transport, deposition of sediment, uplift and subsidence
500
Artificial barriers like jetties produce deposition and depletion. Which is produced updrift, and which downdrift?