Quiz Nov 19

Question 1

What are tsunamis and seismic sea waves caused by?

Answer 1

caused by water displacement

Question 2

Tsunami

Answer 2

Long-wavelength (up to 200km)

shallow-water, progressive waves caused by the rapid displacement of ocean water

They can move at speeds over 800 km/h

Can reach a height of up to 30 meters

Question 3

Seismic sea waves

Answer 3

Tsunami generated by sudden, vertical movement of earth along faults

Question 4

What are the longest ocean waves?

Answer 4

Tides

Question 5

Newton’s Law of Universal Gravitation

Answer 5

All objects attract each other with a force of gravitational attraction. Gravity
is universal. This force of gravitational attraction is directly dependent upon the masses of both objects and inversely proportional to the square of the distance that separates their centers.

Question 6

Black hole

Answer 6

A body with immense mass, so big that not even the light escapes of it ́s gravity

Question 7

Tides

Answer 7

Periodic, short-term changes in the height of the ocean surface at a particular place. Their wavelength can equal half of Earth’s circumference

Question 8

what are tides caused by

Answer 8

They are caused by a combination of the gravitational force of the moon and sun and the motion of Earth

gravity and inertia

Question 9

The equilibrium theory/model of tides

Answer 9

explains the tides based on the gravity and inertia generated by the position and attraction of Earth, moon and sun.

Does not factor the ocean depth or the position of land masses.
Assumes (wrong) that:
1) The sea floor does not influence the tides.
2) The ocean conforms instantly to the forces that affect the position of its surface.
3) The ocean surface is presumed to be in equilibrium with the forces acting on it.

Question 10

In the equilibrium model:

• Gravity and inertia (centrifugal force):

Answer 10

gravity pulls the Earth and the moon towards each other, but inertia keeps them apart.

Question 11

• In the equilibrium model:

* The moon?

Answer 11

does not revolve around the center of the Earth
• Rather, the Earth moon system revolves once a month around the systems center of mass, located 1650 km inside the Earth

Question 12

The moon’s gravity?

Answer 12

The moon ́s gravity attracts the ocean surface towards the moon = first tidal bulge

Question 13

Earths motion causing second bulge. how?

Answer 13

Earth ́s motion around the center of mass of the Earth-moon system throws
a bulge in the opposite side of Earth (Inertia) = second tidal bulge • The result are 2 tidal bulges

Question 14

High tide

Answer 14

the crest of the planet-sized waves formed by the attraction of moon ́s gravity in equilibrium with inertia (every 6 hours approx.)

Question 15

Low tide

Answer 15

the troughs of the planet-sized waves formed by the attraction of moon ́s gravity in equilibrium with inertia (every 6 hours approx.)

Question 16

What influences the tides

Answer 16

both sun and moon

Question 17

spring tides

Answer 17

caused by the linear alignment of the sun, Earth and moon. High tides are very high, low tides are very low, corresponding to full and new moons

Question 18

neap tides

Answer 18

occur when the moon, Earth and sun form a right (90o) angle. High tides are not very high, low tides are not very low

Question 19

The dynamic theory of tides

Answer 19

Explains the difference between observed tide behavior (2 m tide variation in average) and predictions based on the equilibrium theory (lunar tide = 55 cm; solar tide = 24 cm). Considers that: 1) Ocean surface never comes to equilibrium: Sun and moon change positions so rapidly that the water cannot keep up with their “movement”. 2) Tidal crest velocity is determined by ocean depth because the ocean is shallower than half of its wavelength. 3) As Earth turns, continents obstruct tidal crests

Question 20

• Astronomical tide

Answer 20

tides caused by inertia and gravitational force of moon and sun

Question 21

• Meteorological tide

Answer 21

variation of tide height caused by a storm (storm surge)

Question 22

semidiurnal tides

Answer 22

two high tides and two low tides of nearly equal level each lunar day

Question 23

diurnal (daily) tides

Answer 23

one high, one low

Question 24

Semidiurnal/mixed tidal pattern

Answer 24

when successive high or low tides are of significantly different heights throughout the cycle (diurnal+semidiurnal tides)

Question 25

Amphidromic points (AP)

Answer 25

No-tide points at the ocean around which the tidal crest rotates through one tidal cycle (counterclockwise in N Hemisphere, clockwise in S Hemisphere)

Question 26

Tidal range

Answer 26

the height difference between high and low tides

Question 27

In a narrow and restricted basin…

Answer 27

tide crest cannot rotate around an AP and water simply moves in and out of the bay

Question 28

tidal bore

Answer 28

forms in some inlets exposed to great tidal fluctuation

Question 29

Tidal currents in bays and harbors

Answer 29

FES

• Flood current — tide crest into enclosed area rising sea level
• Ebb current — tide trough – water rushing out of the enclosed area
• Slack water — a time of no currents

Question 30

How are tides predicted

Answer 30

Study of past records permits prediction of tidal height to an accuracy of about 3 centimeters (1.2 inches) for years in advance.

Question 31

Tidal datum

Answer 31

reference level to which tidal height is compared.

Question 32

king tides

Answer 32

Spring tides are greater in the Northern Hemisphere in winter than in the summer, because Earth is closest to the sun.

Question 33

tidal range

Answer 33

the height difference between high and low tides.

Increases with the distance from an amphidromic point. Largest in ocean basins. Extreme tides: 15 m

Question 34

Why the Caribbean doesn ́t have such great tides?

Answer 34

not so much topography to alter the way the tidal bulge is distributed.

Channels between island will routinely see higher currents than surrounding areas because more water has to get between the islands to normalize the height

Question 35

How long does the rotation of the sun take?

Answer 35

1 year