Oc 332 Midtern 1

Front 1

ways that the bathymetry of the ocean has been measured

Back 1

sounding-letting a weight come out of a ship and hit the bottom
sonar
topography from satellite

Front 2

problems with soundings

Back 2

boat drifting
current in lower layers

Front 3

why is there a density difference between continental and oceanic crust

Back 3

continental crust is composed of granite, which is lighter than the basalt that makes up oceanic crust

Front 4

Explain the topography around a continent and extending into the ocean

Back 4

there is a shallow continental shelf, leading to a shelf break, continental slope, and eventually either to a trench, contiental rise, or abyssal plain

Front 5

evidence for plate tectonics

Back 5

earthquakes
similarities between species across basins
age of ocean crust
magnetic anomalies
hot spots

Front 6

what causes the movement of lithospheric plates

Back 6

convention in the mantle caused from heat from radioactive decay at the core of the earthg

Front 7

why is oceanic crust more dense the farther it is away from a ridge

Back 7

because as it cools, the rock beceomes more dense and also it accumulates sediment that makes it heavier

Front 8

what land location is where convergent boundaries are usually found

Back 8

on coastlines where ocean meets continental crust

Front 9

are volcanoes found at convergent or divergent boundaries?

Back 9

convergent. a lot of the oceanic crust which contains water and sediment that has a lower melting point, begins to melt from the friction, leading to bubbling that produces volcanoes

Front 10

transform fault`

Back 10

when two plates slide past each other

Front 11

isostatic leveling

Back 11

responses of a plate rising or falling on the athenosphere due to changes in density. this relies on the principle of archimedes where the force pushing up an object to be buoyant is equal to the weight of fluid that the object displaces.

Front 12

active margin

Back 12

a convergent boundary where an oceanic plate is crashing with a continental plate
narrow continental shelf

Front 13

passive margin

Back 13

no crashing between plates
there is no seismic activity
no trenches
there is a wide continental shelf

Front 14

amplitude of a wave

Back 14

half of height

Front 15

wavelength

Back 15

distance from a peak to a peak

Front 16

equation for frequency

Back 16

T= 1/f

Front 17

wave speed

Back 17

C= wavelength / time

Front 18

wave steepness

Back 18

amplitude / wavelength

Front 19

what is the path of a water molecule in wave?

Back 19

one circle

Front 20

draw a diagram of a wave and draw the velocity vectors

Back 20

done

Front 21

what is a wave

Back 21

a disturbance or vaiation that transfere energy progressively from point to point in a medium

Front 22

What propagates in a wave?

Back 22

not the water itself, but the form of waves

Front 23

crest

Back 23

highest point on the wave

Front 24

trough

Back 24

lowest point on a wave

Front 25

height of a wave

Back 25

vertical distance between crest and trough

Front 26

amplitude

Back 26

half of height

Front 27

wavelength

Back 27

distance between adjacent wave crests

Front 28

wave period

Back 28

the time between the arrival of succesive wave crests

Front 29

wave frequency

Back 29

the number of waves in a cycling passing a given point at each second

Front 30

wave phase speed

Back 30

c = L/ T (wavelength divided by time)

Front 31

what do waves travel through

Back 31

sometimes directly through a medium (sound). some will travel along the boundary between two different media (waves on a puddle)

Front 32

what is needed in order for a wave to occur

Back 32

a disturbance
a restoringforce
a means for the energy to travel away from the source

Front 33

what is a restoring force

Back 33

a force that gives rise to equilibrium in a system. For waves, it is a force that tends to return a sea surface to its original flat state.

Front 34

what are restoring forces for the ocean

Back 34

gravity
surface tension
earth's rotation

Front 35

how does surface tension act as a restoring force

Back 35

it acts similarly to a trampoline, causing a depression to "snap back"

Front 36

how does gravity act as a restoring force

Back 36

Gravity causes a pressure gradient from the top of a wave height to the trough of a wave. Water that is piled up at the crest has more pressure on water molecules, than at the trough. Pressure gradients move from high pressure to low pressure

Front 37

what kind of energy does a molecule have at the top of a wave

Back 37

potential

Front 38

what kind of energy does a water molecul have at the bottom of a wave

Back 38

kinectic

Front 39

what causes a wave

Back 39

a disturbance where the sea surface is displaced

Front 40

what are examples of a wave disturbance

Back 40

wind
verical displacement
something that causes a pressure disturbance

Front 41

the diameter or water molecule orbit circulation is halved how far in the water column?

Back 41

1/9 of the wavelength

Front 42

At what depth does a wave orbit become flattened?

Back 42

half the wavelength

it becomes a surge back and forth

Front 43

explain wind waves and how they disturb

Back 43

small variation in wind speed and pressure that occur across a smooth surface causes capillary waves to develop. atmospheric pressure is generated on the faceward side of the wave that essential becomes pushed, while the leeward side there is an a lower pressure. As always, pressure moves from high to low.

Front 44

Waves between what period have the most energy

Back 44

0.2 and 30 seconds

Front 45

what is the equation for wave spped that takes into accound depth and wave length

Back 45

c = sqrt ( (gL/2pi) * tanh (2pid/L))

Front 46

What is qualifies as a "deep" wave

Back 46

d > L/2

Front 47

what is the approximation for wavespeed of a deep water wave

Back 47

c = sqrt (gL/2pi)

Front 48

What qualifies as a "shallow" wave

Back 48

d < L/20

Front 49

What is an approximation for wave spped of a shallow wave

Back 49

c = sqrt (gd)

Front 50

what is the motion of a shallow water wave

Back 50

elliptical

Front 51

why doesn't the ocean look like smooth singular waves moving across the surface?

Back 51

because of interference

Front 52

phase velocity

Back 52

velocity of wave peaks

Front 53

group velocity

Back 53

velocity of wave packet

Front 54

when the phase velocity doesn't equal the group velocity what speed does the wave energy travel at?

Back 54

the group velocity

Front 55

in deep water, group velocity =

Back 55

1/2 phase velocity

Front 56

in shallow water, group velocity =

Back 56

phase velocity

Front 57

what is a rogue wave

Back 57

a wave that results in the addition of many waves and is extremely large in comparison to the "norm" of waves

Front 58

what causes waves to break

Back 58

because the waves become too steep and top starts having a faster velocity than the rest of the wave.

this occurs at H/L = 1/7 or about 120 degrees

Front 59

what are the wind factors that control wave growth

Back 59

strength
duration
fetch (distance over which the wind blows unimpeded across the water)

Front 60

fetch

Back 60

distance over which the wind blows unimpeded across the water

Front 61

beaufort scale

Back 61

on a scale of 0 to 12 it measures the intensity of at sea weather. this is usually a response to the sea by wind forcing

Front 62

what limits the height of waves in shallow water

Back 62

water depth

Front 63

what is a fully developed sea

Back 63

ocean waves are so energetic that input from the wind = losses due to wave breaking

Front 64

in the equation for wave phase speed what does L and T stand for?

Back 64

wavelength = L
period = T

Front 65

what limits the fetch of wind?

Back 65

In the N or S direction it is limited by the fact that wind is in bands along the earth, like the tradewinds and the westerlies

Landmasses and reefs alter the travel of a wave

Front 66

Why are higher waves more common in the pacific

Back 66

because the atlantic and indian oceans are more narrower and provided a limited fetch

Front 67

In deep water, are long waves or short waves faster?

Back 67

long waves

Front 68

Waves in Oregon originate from where?

Back 68

Storms in the Gulf of Alaska or Baja California

Front 69

Explain the presence of kinectic and potential energy in a wave

Back 69

kinetic energy is due to the motion of water particles in waves

potential energy is due to the changing height of particles throughout that motion

Front 70

What is the equation for wave energy

Back 70

E= 1/8 density *g*wave height (H)

Front 71

Wave power

Back 71

the rate at which energy is propogated, per unit lenght of a wave crest

P = c*E

Front 72

How does current effect wave height

Back 72

When wave motion is opposite of the direction of the current, then wavelength shortens, leading to an increase in wave height.

Front 73

significant wave height

Back 73

measure of the average height of the highest one third of all waves within a given area at a specific time

Front 74

Explain what wave shoaling is

Back 74

Wave shoaling is the process where wave height changes in response to a change in water depth.

This is best illustrated through a wave coming to shore. As the waves come into shore, they interact with the bottom. The friction of the bottom causes the waves to slow down, leading to a decrease in wavelength. However, energy is conserved, so energy instead is transferred to height.

Eventually, maximum steepness occurs, leading to the top of the wave moving faster than the bottom, causing breaking

Front 75

Why do waves flow mostly parallel to the shore?

Back 75

This occurs due to wave refraction. As one portion nears the shore quicker than another point in a wave, it slows down, while the faster points catch up until they are all traveling at the same speed.

Front 76

What causes a wave to dissipate?

Back 76

Viscosity between water molecules. (Internal friction)

Friction with other surfaces

Front 77

In a wave train, how is energy transferred

Back 77

some is transferred forward to intiate orbital motion in undisturbed water molecules, but the other half of the energy is transferred back to the second wave in the train

Front 78

wave trains

Back 78

a group of waves traveling together

Front 79

What is a result of the energy being transferred in a wave train

Back 79

the leading wave loses energy, causing it to lose height and eventually dissipate

Front 80

What is another way to think of the relationship that group velocity is 1/2 of the phase velocity

Back 80

the speed that a wave train moves at is 1/2 the speed of an individual wave

Front 81

Why do longer period/wavelength waves arrive before shorter period/wavelength waves at a given locatin?

Back 81

Because in deep water, waves with longer periods and greater wavelengths contain greater energy and travel faster

Front 82

in waves that are in a water depth of less than L/20, what controls wave speed

Back 82

water depth

Front 83

What way do wave rays bend in shallow water?

Back 83

towards shallower water

Front 84

How does refraction affect wave energy

Back 84

In deep water, a wave has the same amoutn of energy per unit length along the entire wave crest. When the wave is refracted, energy is conserved, and as the length of the wave is increased, the wave height decreases.

Front 85

What causes the shape of breaking waves

Back 85

the slope of the beach

Front 86

Spilling breaker

Back 86

a wave break that is formed when the sea bottom is almost flat. The wave height reaches a bottom depth about 1.2 times its height and it becomes unstable

Front 87

Plunging breaker

Back 87

Have the spectacular curl

Formed on seafloor that is moderately steep.

As the wave approaches the slope, the bottom of the wave is slowed faster than the top, causing the wave crest to curl over

Front 88

Collapsing breaker

Back 88

rare waves that occur when the seafloor has a steep slope. What happens is the bottom of the wave slows down so quickly that the leading face collapses before the wave crest can eve break.

Front 89

Surging breaker

Back 89

occurs on very steep slopes where waves appear not to break at all

Front 90

Set down

Back 90

the gradual shoreward decrease in the mean sea level height

Front 91

set up

Back 91

an increase in mean sea level height, found within the surf zone

Front 92

explain rip currents

Back 92

Wave breaking causes a build up of water near shore, leading to a pressure gradient from near shore to off shore. This water eventually breaks through the surf, preferrably in an area where wave heights are low. These narrow jets are called "rip currents."

Front 93

Wave diffraction

Back 93

when a wave encounters an obstacle it will bend around it

Front 94

What is a standing wave?

Back 94

the sum of two waves traveling in opposite directions

Front 95

node

Back 95

a place of intersection where waves cancel each other out. the motion is stationary

Front 96

antinode

Back 96

place of maximal amplitude, located halfway between each node

Front 97

In a standing wave, where is the speed the greatest

Back 97

at the node

Front 98

in a standing wave, where is the speed zero

Back 98

at an antinode

Front 99

seiches

Back 99

stationary waves in basin modes

Front 100

what are standing waves important in basins

Back 100

they can grow to be quite large

Front 101

Tsunamis are generated from what?

Back 101

seismic events such as an earthquake or landslide causes a large displacement of water

Front 102

Are Tsunamis deep water or shallow water waves?

Back 102

tsunamis are shallow water waves because they have a very long wave length (100 to 200 km) and have large periods (10 to 30 minutes). Because most of the ocean floor is less than 4 km deep, most of the ocean floor is less than one twentieth of the wavelength of a tsunami.

Therefore: c = sqrt (g * D)

Front 103

What causes a Tsunami to get its incredible size?

Back 103

As the tsunami enters shallower water, it's wavelength is reduced, but its period is unchanged (like any other wave), leading to an increase in wave height.

Front 104

internal waves

Back 104

waves occurring at the boundary of a pynocline: where two distinct different densities meet.

Front 105

slick

Back 105

surface visual of an internal wave

Front 106

What is the speed of internal waves? What does it depend on?

Back 106

They are usually slow, because the depend upon a difference in the density between upper and lower layers

Front 107

A slick represents what portion of an internal wave?

Back 107

the trough of an internal wave

Front 108

explain the idea of stokes drift

Back 108

waves are more complex than pure sine waves, which are closed paths (begin and end at same place). Instead the orbits don't quite closed, leading to some forward motion by the object in the path.

Front 109

Explain stokes drift

Back 109

That a water particle does not travel in a pure sine wave pattern where it ends up exactly where it began. Instead the orbits aren't closed and result in a slightly forward motion of an object floating on the surface of the water

Front 110

what are ways that the tide is measured

Back 110

-tide stations have have a pully with a counterweight
-acoustic sensors
-pressure gaugesq

Front 111

What are some potential problems with measuring the tide in a tide station

Back 111

stations are located near river mouths which could cause a change in sea height

there could be wave interference

Front 112

What causes differences between predicted and observed tides

Back 112

storm surge --> (set up)

low atmospheric pressure zone (rise in sea water level)

Front 113

ebb vs flood

Back 113

flood is the coming in of the tide
ebb is the going out of the tide

Front 114

What is a tide?

Back 114

a very long ocean wave

wavelength is about 1/2 of the earth's circumference

Front 115

diurnal tide

Back 115

one change in the tide a day

Front 116

semidiurnal tide

Back 116

two low and high tides in a tide

Front 117

mixed tides

Back 117

have two low and high tides, but at different heights

Front 118

explain the equilibrium theory of tides

Back 118

note: oversimplified to explain priniciples

-no continents w/ water at uniform depth
-ignores friction
-assumes instantaneous equilibrium

Front 119

newtons law of gravitation

Back 119

f = G x (M1 x M2)/D2

D= distance between two
G = gravitational constant
M1 and M2 are the masses of the objects

Front 120

How does gravity and centrifugal force affect tides?

Back 120

The moon and the sun exert a gravitational force, as described by newton's law of gravitation.

Centrifugal forces results from the rotation of two bodies about each other. When two bodies are of unequal weight, their common point of rotation is located closer to the heavier object (in this case, earth (moon) and sun (w/ earth)) The centrifugal force is the force pulled inward to that common point of rotation. In the case of the Earth, everything is unaffected by this gravitational pull except water, which is constantly in motion. This results in a buldge

Front 121

spring tides

Back 121

largest tidal range

Front 122

neap tides

Back 122

smallest tidal range

Front 123

how much force does the sun exert on the earth in comparison with the moon?

Back 123

1/2 of the moon's force

Front 124

syzygy

Back 124

when the moon and sun and earth are almost aligned

Front 125

explain the difference between a spring and neap tide, what is occuring?

Back 125

During a spring tide, the sun, moon, and earth are aligned. This causes the bulge to be magnified on the earth. As a result, high tides are higher and low tides are lower.

During a neap tide, the moon and sun are 90 degrees apart with respect to the earth, leading to a reduced high tide, and raised low tide.

Front 126

How often to spring tides occur in a lunar cycle?

Back 126

1/2 a lunar cycle

Front 127

how long is a lunar cycle

Back 127

29.5 days

Front 128

What depicts whether a point on the Earth will experience a diurnal, semidiurnal, or mixed semidiurnal tide?

Back 128

It depends upon where the point is located latitudinally with respect to the lunar tidal bulge. A point at the top or bottom of the earth has less distance to travel than a point at the equator of the earth. Therefore, A experiences a smaller portion of the lunar bulge, most likely leading to a diurnal tide pattern

Front 129

Definition of Centripetal Force

Back 129

It is the force towards the center that glues an object in a circular path

Front 130

define centrifugal force

Back 130

it is an imaginary force that counteracts the centripetal force. It is the force away from the center

Front 131

Tides explanation in terms of centripetal force

Back 131

Gravitational force is different for individual points on the earth. This happens because the distance between the moon and a given point on the earth can change. Centripetal force, which in the case of tides is the force towards the moon, is the same at every point on the earth. The discrepancy between these two forces is what causes a pressure gradient which is the "tide-generating force."

Front 132

Tides explanation in terms of centrifugal force

Back 132

Centrifugal force, which is opposite to centripetal force, is constant at every point on the Earth, while gravitational force is not. Also, the direction of the moon's gravitational force is always pointing towards the center of the moon. This creates different vector angles for the gravitational force at different places on the Earth. Centrifugal force vectors are all parallel. The resultant force between the centrifugal and gravitational force creates the "tide-generating force."

Front 133

explain the dispersal of a tide generating force

Back 133

At the points closest and farthest away from the moon, the centrifugal and gravitational forces are parallel,but in opposite directions. While the forces are the strongest at this point because it is closer to the moon, the cancellation of these two forces makes the net tide generating force small, almost negligable.

However, at points farther away from the moon, the gravitational force and centrifugal force are not in complete alignment. (grav force points towards center of the moon) This reduces cancellation, strengthening the tide generating force.

The result of this process is that water has a net movement towards the points that are the furthest and closest to the moon. This causes bulging at those points.

Front 134

Why are the tides separated by 12 hrs and 25 minutes?

Back 134

The moon travels around the earth in 24 hours and 50 minutes. (a lunar day) This is why high tides and low tides will occur at different times each successive day.

Front 135

What causes two different heights of two daily high tides?

Back 135

The moon's orbited is tilted with the respect to the Earth's axis by 25 degrees. This causes a point to experience different portions of the lunar tidal bulge as the earth rotates. See figure 12.8 on page 320 of the textbook. Observe point C1. It is located within the bulge, which will experience a high tide, but the point C3, which is another high tide, experiences less of the bulge, causing its high tide to not be a strong.

Front 136

What depicts whether a point on the Earth will experience a diurnal, semidiurnal, or mixed semidiurnal tide?

Back 136

It depends upon where the point is located latitudinally with respect to the lunar tidal bulge. A point at the top or bottom of the earth has less distance to travel than a point at the equator of the earth. Therefore, A experiences a smaller portion of the lunar bulge, most likely leading to a diurnal tide pattern.