Transcript waves
Unit 7
Waves & Beaches
Topic 1 Watching Waves
Surf zone is the area near shore where waves break.
How far from shore a wave breaks depends on the
length of the wave and the depth of the water.
How a wave breaks depends on the:
– steepness of the bottom slope
– whether the slope is smooth or irregular
– whether the bottom is composed of shifting sand or solid rock
Waves may break more than once as they come
to shore.
Each time it breaks, it gives up energy and
becomes smaller and shorter.
Types of Breaking Waves
Plunging waves
– Occurs when the swell comes
out of deep water and hits a
shallow sandbar or reef.
– Form where there is a
moderately steep, sloping
bottom.
– Form tubes or curls that cascade
water in a circular motion
downward into the trough and
break forcefully with a rapid
release of energy.
– If the bottom is very steep, the
top of the wave may break over
the lower half forming a
Collapsing wave with no curl.
Ultimately, these are the
waves that surfers look for.
They break top to bottom
and tend to be faster and
more challenging.
Spilling breakers
– They form where the bottom slopes gradually.
– These waves advance to shore with a line of
foam down their front.
– They break slowly over long distances
– The wave energy is gradually released over time
and the beach.
– This type of surf is best for landing craft.
Break slowly
Break rapidly
Surging breakers
– Steep beach slope
– They form when large waves
suddenly hit bottom in shallow
water.
– Wave does not break - surges up to beach
Example: Tsunami and tidal bores(occurs where a river empties
into an ocean/sea. A tidal bore is a strong tide that pushes up the
river, against the current. They are true tidal waves. A tidal bore
creates a surge or a sudden change in depth.
– which look like walls of water advancing toward shore.