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Water levels and flow > 2: tides > Flashcards

2: tides Flashcards

(58 cards)

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1
Q

What are the main celestial bodies influencing tides?

A

The Moon, the Earth, and the Sun.

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2
Q

What assumption is made about Earth when explaining basic tide generation?

A

Earth is a perfect sphere covered in water with no continents or rotation.

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3
Q

Why does the Earth experience a centrifugal force?

A

Because the Earth and Moon revolve around a common center of mass (barycenter).

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4
Q

Where is the Earth-Moon barycenter located?

A

About 4670 km from the Earth’s center, within the Earth.

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5
Q

Is centrifugal force equal across the Earth?

A

Yes, it’s the same for all points.

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6
Q

Is gravitational force equal across the Earth?

A

No, it’s stronger on the side closer to the Moon and weaker on the far side.

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7
Q

What causes the tidal bulges?

A

The imbalance between centrifugal and gravitational forces.

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8
Q

How many tidal bulges are there?

A

Two – one facing the Moon, and one on the opposite side.

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9
Q

Which component primarily causes tides: tangential or normal?

A

Tangential component.

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10
Q

Why are there two high tides per day?

A

Due to Earth’s rotation through the two tidal bulges.

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11
Q

What is the period of a tidal day?

A

24 hours and 50 minutes.

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12
Q

How does the Sun’s effect on tides compare to the Moon’s?

A

The Sun has about 46% of the Moon’s effect.

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13
Q

What is a spring tide?

A

A tide with the greatest tidal range, occurring when the Sun, Moon, and Earth are aligned.

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14
Q

What is a neap tide?

A

A tide with the smallest tidal range, when the Sun and Moon are at 90° angles.

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15
Q

When do spring tides occur?

A

During new and full moons.

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16
Q

When do neap tides occur?

A

During the first and last quarter moons.

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17
Q

What is priming?

A

High tide occurs before the Moon is overhead.

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18
Q

What is lagging?

A

High tide occurs after the Moon is overhead.

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19
Q

What is the Saros cycle?

A

A ~18-year cycle relating to eclipse recurrence and tidal variations.

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20
Q

What is the nodal cycle?

A

An 18.6-year cycle related to the Moon’s orbital nodes affecting tides.

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21
Q

What is the metonic cycle?

A

A 19-year cycle related to repeating lunar phases.

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22
Q

What are the two major causes of sea level rise?

A

Thermal expansion of water and melting of land-based ice.

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23
Q

What is the predicted sea level rise by 2100 (IPCC 2021)?

A

40 to 100 cm, depending on scenario.

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24
Q

How much has sea level risen since the last ice age?

Study These Flashcards
A

Over 100 meters.

25
What is a semi-diurnal tide?
Two high tides and two low tides each tidal day.
26
What is a diurnal tide?
One high tide and one low tide each tidal day.
27
What is a mixed tide?
Tides with unequal high and low water levels in the same day.
28
What is a microtidal range?
Tidal range less than 2 meters.
29
What is a mesotidal range?
Tidal range between 2 and 4 meters.
30
What is a macrotidal range?
Tidal range greater than 4 meters.
31
What is a tidal bore?
A sudden surge of water in an estuary during strong flood tides.
32
Where can tidal bores occur?
In estuaries with specific shapes and large tidal ranges, e.g., Severn, Gironde.
33
What causes crosscurrents in the Scheldt estuary?
Strong spring tides and estuary geometry.
34
What is the formula for centrifugal force?
F = m * ω² * r, where m is mass, ω is angular velocity, and r is radius.
35
What is the formula for gravitational force?
F = G * (m1 * m2) / r²
36
Why is the gravitational force different across Earth?
Because distance to the Moon varies depending on the location.
37
Where is gravitational force strongest on Earth?
On the side facing the Moon.
38
Where is gravitational force weakest on Earth?
On the side opposite the Moon.
39
What causes the residual tidal force?
Difference between gravitational and centrifugal forces.
40
What shape does the tidal potential create on Earth?
An oval with bulges on opposite sides.
41
What is the tangential component of tidal force responsible for?
Driving the flow of water that forms tides.
42
What is the angle between Earth's rotation axis and the ecliptic?
23.44 degrees.
43
What is the angle between the Moon's orbital plane and the ecliptic?
5.1 degrees.
44
What is the perigee?
The closest point of the Moon to Earth (about 357,000 km).
45
What is the apogee?
The farthest point of the Moon from Earth (about 406,000 km).
46
What is the aphelion?
The point where Earth is farthest from the Sun.
47
What is the perihelion?
The point where Earth is closest to the Sun.
48
What is a sidereal day?
Time Earth takes to rotate 360° relative to stars (~23h 56m).
49
What is a synodic month?
Period between two new moons (~29.53 days).
50
What is a draconic month?
Time between two passages through the ascending node (~27.21 days).
51
What is a sidereal month?
Time for the Moon to complete one orbit relative to stars (~27.32 days).
52
What is a tropical year?
Time between two vernal equinoxes (~365.24 days).
53
What is the effect of elliptical orbits on tidal forces?
Closer distances increase gravitational pull, enhancing tides.
54
How much did sea level rise from 1950 to 2009?
About 1.7 mm per year.
55
What are IPCC's latest sea level rise projections (2021)?
Between 40 and 100 cm by 2100.
56
How do nodal cycles affect tide measurements?
They introduce an ~18.6-year oscillation of a few centimeters.
57
What is the effect of sea level rise in the Scheldt estuary?
Increases in high water levels by 60–100 cm over the past century.
58
Why are nodal cycle effects important in tide modeling?
To avoid misinterpreting them as long-term sea level trends.

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