Chapter 12 - waves and tides

What is a storm surge?

A destructive wave that forms when high winds push water against the shore, where it piles up. The shallower the water off shore, & the further extends off shore the greater the surge.

What is a standing wave?

A standing wave is a vertical oscillation in which water rocks back and forth, rising and falling at the ends but relatively motionless near the center

What causes tsunamis?

A tsunami results from sudden water displacement caused by a landslide, an iceberg falling into the sea from a glacier, a volcanic eruption, or, most commonly, an earthquake.

What makes a wave break?

A wave breaks when its H:L ratio exceeds the 1:7 ratio when the depth is 1.3 times the height.

What is a wave?

A wave is the transmission of energy through matter. When energy moves through matter as a wave, the matter moves back and forth, or rotates but then it returns to its original position.

Spring tides

Both positions create the highest and lowest tides called the spring tides.

What happens when there is a new moon?

Both the sun and moon are aligned on opposite sides of the earth

Three basic types of breakers; plunging breakers

Characterized by a curl as the top of the wave pitches through the air before splashing into the bottom. They occur on moderately steep breaches.

Three basic types of breakers; spilling breakers

Characterized by the top of the wave tumbling and sliding down the front of the wave as it decelerates slowly. They occur on moderately steep breaches.

Daily tides

Create a current that flows into and out of bays, rivers, harbors, and other restricted areas.

What are the differences between deep water waves and shallow water waves?

Deepwater waves occur in water that is deeper than half their wavelength, while shallow water waves occur in water that is shallower than one twentieth of their wavelength. In deep water the bottom does not affect their orbital moon, while in shallow water moves the bottom creates drag that affects their orbital motion.

What disturbing forces cause waves?

Disturbing forces that cause ocean waves include wind, changes in gravity, and seismic activity.

What are diurnal, semidiurnal, and mixed tides?

Diurnal tides are single high and low tides that occur daily. Semidiurnal tides are two roughly equal high and low tides that occur daily. Mixed tides are two unequal high and low tides that occur daily.

Equilibrium theory

Explanation for the tides

What are seiches?

Form in-bodies of water smaller than an ocean as a wave that rocks back and forth. It results from a strong wind that pushes the water level up on the side of a lake or bash.

Diurnal tides

Having a single low and high tide daily (Gulf Of Mexico)

Mixed Tides

Having two unequal high and low tides daily ( West coast of US)

What was the equilibrium theory?

His theory assumed that the Earth is perfectly uniform, that water is very deep and that there are no land masses.

How do wavelength and period relate to a wave's speed?

If you know the wavelength and the period, you can determine the speed of waves. ( Speed = wavelength / period )

What causes internal ocean waves?

Internal ocean waves can occur within different density layers. Scientists don't know exactly what causes internal waves. It is likely that they get their energy mostly from tides and storms. Breaking internal waves mix the ocean and drive deep circulation.

Who proposed the Equilibrium theory?

Isaac Newton

What happens when the moon is in a quarter phase?

It and the sun are at a right angle to the earth

What was the problem with the equilibrium theory?

It was too simplistic.

Important points to the dynamic theory:

Laplace's model is called the dynamic theory which shows that there aren't only two tidal bulges; rather, there are several tidal bulges.

Dynamic theory

Modified Newtons model to account for tidal variations.

What are the relative positions of the sun and moon during spring tides and neap tides?

Neap tide: Moon, space, and sun are at a right angle. Spring tides: New moon- moon and sun aligned on the same sides. Full moon- sun and moon aligned on opposite sides.

How does Newton's equilibrium theory of the tides differ from Laplace's dynamic theory?

Newton's equilibrium theory was too simplistic. Newton merely stated that, Earth is perfectly uniform, water is deep, and there are no landmasses. Laplace elaborated much further, accounting for tidal variations.

How waves hit a shore ! - Reflection

Occurs when waves hit an abrupt that is nearly perpendicular in the water, such as a sea wall reflected wave energy can bounce around the sides of an enclosed area creating complex wave patterns.

How waves hit a shore ! - Diffraction

Occurs when waves hit an obstacle, such as a jetty. Energy shifts within the wave, allowing a new wave pattern to form past the obstacle or through an opening.

Who proposed the dynamic theory?

Pierre Simon Laplace

What are amphidromic points?

Points where water doesn't rise and fall with the tides.

How waves hit a shore ! - Refraction

Refraction concentrates wave energy toward protrusions because the side of the wave nearest to the protrusion slows first, turning the wave toward it.

How do wave refraction, diffraction, and reflection affect the behavior of waves?

Refraction is the bending of ocean waves. Diffraction occurs when waves pass an obstacle, such as a jetty or a point of land. Energy shifts within the wave, allowing a new wave pattern to form past the obstacle or through an opening. Reflected wave energy can bounce around the inside of an enclosed area, creating complex wave patterns.

What restoring forces cause waves?

Restoring forces that resist ocean wave formation include gravity, coriolis effect, and surface tension.

What are tsunamis ?

Result from sudden water displacement caused by a landslide, iceberg, volcanic eruption, or, more commonly, an earthquake.

Tides

Result from the gravitational pull of the moon and, to lesser degree, the sun.

How can a fully developed sea have waves that are bigger or smaller than the maximum theoretical size?

Scientists believe such a rogue wave results from the interaction of two closely related wave trains. When wave trains come together from different areas, they affect each other in the form of constructive or destructive interference.

What causes seiches?

Seiches form in large bays and lakes as a wave that rocks back and forth, can result from a local earthquake and a strong wind that pushes the water level up on one side of a lake or basin.

What causes storm surges?

Storm surges are caused by wind pushing water against shore, where it piles up.

What happens when a wind wave breaks on shore?

The H:L ratio exceeds 1:7. the water depth is 1.3x the wave height. The top of the wave is traveling more quickly than the bottom. Contact with bottom decreases the wavelength and increases the height.

What happens due to drag from the seafloor?

The bottom of the wave slows so that the top of the wave is travelling faster than the bottom. This, and exceeding the 1:7 ratio, makes the wave break, toppling the upper part of the wave forward.

What are the crest, trough, height, wavelength, period, and frequency of a wave?

The crest is the highest point above the average water level, the trough is the lowest point, and the height is the vertical distance from the trough to the crest. Wavelength is horizontal distance between the identical points on two waves. Period is the amount of time it takes for the same spot on two waves to pass a single point, while frequency is the number of waves that pass a fixed point in one second.

What influences besides lunar and solar gravity affect the tides?

The imperfect sphere of earth, the coriolis effect, the season, the time of month, and the shape of the ocean basin.

What happens during a full moon?

The sun and moon are aligned on opposite sides of the Earth

What are three types of progressive waves?

The types of progressive waves are, longitudinal waves, transverse waves, and orbital waves. A longitudinal wave occurs when the matter moves back and forth in the same direction that the energy travels. This type of wave can move through all states of matter, transmitted through the compression and decompression of particles. When transverse waves occur in matter, the motion of the matter is perpendicular to the direction in which the wave as a whole is moving. Orbital waves only transmit through fluids. They occur when energy moves the fluid in a circular motion as it passes.

What are tidal currents and a tidal bore?

There are three tidal currents. Slack- outflow Flood- inflow Slack tide- a midpoint of high and low tides. A tidal bore forms when the incoming tide produces a wave that flows into river or other narrow area. This is a true tidal wave and can be several meters feet high in places.

Neap tide

This tends to raise the low tide and lower the high tide.

What is a standing wave ?

This wave is a vertical oscillation in which water rocks back and forth, rising and falling at the ends, but relatively motionless near the center.

What causes the tides?

Tides result from the gravitational pull of the moon, and to a lesser degree, the sun.

What are amphidromic points?

Tides rotate around more than a dozen amphidromic points. These are points where the water doesn't rise and fall with the tides.

Why are tsunamis always shallow-water waves?

Tsunamis are always shallow water waves because, a tsunamis typical wavelength is about 200 km, while the deepest point in the ocean is merely 11 km. There would be no way to have a deep water tsunami.

Why don't tsunamis destroy ships in the open sea?

Tsunamis don't destroy ships in the ocean sea, because they release their energy at the shore. The tsunami also only surges at shore, where it hurls a tremendous water mass & energy onto land.

What three factors affect the maximum wave size?

Wind speed faster than the wave, wind duration, and fetch (surface area over which wind blows)

disturbing forces

cause waves - wind, gravity, and seismic activity

tidal bore

forms when the incoming tide produces a wave that flows into river or other narrow area. This is a true tidal wave and can be several meters feet high in places.

A fully developed sea can....

have waves larger or smaller than the maximum theoretical size.

parts of a wave; crest:

highest point above average water level.

parts of a wave; wave length

horizontal distance between the identical part of two waves.

where are internal waves found?

inside the ocean; below the surface

Semidiurnal tides

is having two roughly equal high and low tides daily ( East coast of the US)

describe what is meant by a wave

is the transmission of energy through matter. Key word is, through. When energy moves through matter as a wave.

parts of a wave; trough

lowest point below average water level.

longitudinal wave

move through all states of matter and occur when energy moves in the same direction that the energy travels.

deep water waves

occur in water that is deeper than half their wave length, the bottom does not affect their orbital moon.

shallow water waves

occur in water that is shallower than one twentieth of their wavelength, the bottom creates drag that affects their orbital motion.

transverse wave

only transmit through solids. they occur when energy motion moves the fluid in a circular motion as it passes.

The suns gravitational pull....

pulls to the side of the moons tidal bulge.

restoring forces

resist waves - surface tension, gravity, and coriolis effect.

scientists hypothesize that these waves are formed due to....

scientists don't exactly know what causes internal waves. It is likely they get their energy from wind, gravity, or seismic forces, just like surface waves.

What other factors influence tides?

the imperfect sphere of the earth, the seasons, the shape of the ocean basin, and the coriolis effect, all influence the tides.

Flood current

the inflow of a tide is the flood current

slack tide

the midpoint of the flood current and the slack current is the slack tide.

parts of a wave; frequency

the number of waves that pass a fixed a point in one second.

slack current

the outflow of a tide is a slack current

What is fetch?

the surface area over which wind blows.

describe the wave motion in a deep layer

the wave motion in a deep layer can cause a thermocline or halocline to slowly rise and fall as the wave passes.

How high can internal waves be?

these waves can be as much as 30 meters tall

why do internal waves occur?

they can occur within different density layers

parts of a wave; period

time it takes for the same spot on two waves to pass a single point.

parts of a wave; wave height

vertical measurement from tough to crest

what happens if waves are in phase?

wave energies are constructive and combine into larger waves. if waves are out of phase, they can cancel each other out.

In deep water a wave breaks when...

when its height exceeds one seventh of its wave

three factors affecting maximum waves size

wind speed faster than the wave, wind duration, and fetch