Ch2: tides

Question 1

What causes tides on Earth?

Answer 1

Tides are caused by gravitational interactions between the Earth, Moon, and Sun. and centrifugal force

Question 2

How do these forces affect Earth’s surface?

Answer 2

They cause two tidal bulges on Earth’s surface.

Question 3

What is the Earth’s radius?

Answer 3

6378 km.

Question 4

What is the Moon’s radius and distance from Earth?

Answer 4

Radius = 1738 km, Distance = 384,400 km.

Question 5

What is the Sun’s radius and distance from Earth?

Answer 5

Radius = 696,000 km, Distance = 149.6 million km.

Question 6

What is the barycenter?

Answer 6

The common center of mass around which the Earth and Moon revolve.

Question 7

Where is the barycenter located?

Answer 7

Inside the Earth, ~4670 km from its center.

Question 8

What force is generated due to this rotation?

Answer 8

A centrifugal force.

Question 9

Is the centrifugal force the same everywhere on Earth?

Answer 9

Yes, it is identical across the Earth.

Question 10

What causes the residual force?

Answer 10

It’s the difference between gravitational force and centrifugal force.

Question 11

What does the residual force lead to?

Answer 11

The generation of tides.

Question 12

What does the tangential component of force do?

Answer 12

It drives horizontal water movement, leading to tidal bulges.

Question 13

What is the role of the normal component?

Answer 13

It’s too weak to lift water vertically.

Question 14

What causes the bulges on both sides of Earth?

Answer 14

The tangential component of the residual force.

Question 15

How long is Earth’s rotation period?

Answer 15

24 hours.

Question 16

How much does the Moon move daily?

Answer 16

Slightly eastward, causing a tidal cycle of 24h 50min.

Question 17

How many tides occur per day?

Answer 17

Two high tides and two low tides.

Question 18

Which has a stronger effect on tides, Moon or Sun?

Answer 18

The Moon, as it’s closer.

Question 19

What is the Sun’s tidal effect compared to the Moon?

Answer 19

About 46% of the Moon’s effect.

Question 20

What about other planets’ tidal effects?

Answer 20

They have negligible tidal effects.

Question 21

What is Earth’s axial tilt?

Answer 21

23.5° relative to the ecliptic.

Question 22

What is the Moon’s orbit tilt?

Answer 22

5.1° to the ecliptic.

Question 23

What do these tilts affect?

Answer 23

Seasonal and spatial variation in tides.

Question 24

When do eclipses affect tides?

Answer 24

During solar and lunar eclipses when Earth, Moon, and Sun are aligned.

Question 25

How do eclipses affect tides?

Answer 25

They locally and temporarily alter tidal forces.

Question 26

What are the Moon’s perigee and apogee distances?

Answer 26

Perigee: ~357,000 km (stronger tides), Apogee: ~406,000 km (weaker tides).

Question 27

What are the Earth’s perihelion and aphelion effects?

Answer 27

Closer distance = stronger gravitational pull = higher tidal forces.

Question 28

What is a lunar day?

Answer 28

24 hours 50 minutes.

Question 29

What is a sidereal day?

Answer 29

23 hours 56 minutes.

Question 30

What is a solar day?

Answer 30

24 hours.

Question 31

What is a synodic month?

Answer 31

29.53 days (New Moon to New Moon).

Question 32

What is a draconic month?

Answer 32

27.21 days (Moon to same node).

Question 33

What is a sidereal month?

Answer 33

27.32 days (Full orbit relative to stars).

Question 34

What is a tropical year?

Answer 34

365.242 days (calendar year).

Question 35

What is a draconic year?

Answer 35

346.62 days.

Question 36

What is a sidereal year?

Answer 36

365.256 days.

Question 37

When are the highest tides?

Answer 37

Around equinoxes (March 21, September 21).

Question 38

When are the lowest tides?

Answer 38

Around solstices (June 21, December 21).

Question 39

What causes semi-diurnal variation?

Answer 39

Earth’s rotation and tilt.

Question 40

How many tides in a lunar day?

Answer 40

2 high and 2 low tides (not always equal).

Question 41

When do spring tides occur?

Answer 41

When Earth, Moon, and Sun are aligned (new/full moon).

Question 42

When do neap tides occur?

Answer 42

When Moon is at 90° to the Sun-Earth line.

Question 43

How often do spring and neap tides occur?

Answer 43

Twice a synodic month.

Question 44

What is the Saros cycle?

Answer 44

~18 years, used to predict eclipses.

Question 45

What is the Nodal cycle?

Answer 45

~18 years 11 days, affects eclipse timing and tides.

Question 46

What is the Metonic cycle?

Answer 46

19 years, Moon phases repeat on same calendar date.

Question 47

What causes sea level rise?

Answer 47

Thermal expansion and melting glaciers/ice sheets.

Question 48

How much is sea level expected to rise by 2100?

Answer 48

40–100 cm.

Question 49

What are semi-diurnal tides?

Answer 49

2 high and 2 low tides per lunar day (most oceans).

Question 50

What are diurnal tides?

Answer 50

1 high and 1 low tide (polar regions).

Question 51

What are mixed tides?

Answer 51

Unequal 2 high and 2 low tides (complex coastlines).

Question 52

What are microtidal ranges?

Answer 52

< 2 meters.

Question 53

What are mesotidal ranges?

Answer 53

2–4 meters.

Question 54

What are macrotidal ranges?

Answer 54

> 4 meters.

Question 55

What is a tidal bore?

Answer 55

A wave caused by sudden water level rise in estuaries with large tidal range.

Question 56

What mainly causes tides?

Answer 56

Gravitational pull of Moon and Sun + centrifugal force from Earth’s rotation.

Question 57

What enhances or reduces tides?

Answer 57

Alignment, distance, orbital cycles, tilts.

Question 58

How is climate change connected to tides?

Answer 58

Rising sea levels increase tidal risks to coasts and estuaries.