Lecture 2 - Astronomical tides

Question 1

Newton’s Law of universal gravitation definition

Answer 1

Earth’s interaction with moon and sun
Relationship between two bodies of certain mass and radius between them
Stronger forced exerted on Earth by moon than sun

Question 2

Newton’s law of universal gravitation equation

Answer 2

F1 = F2 = G M1 x M2 / r2

Question 3

Earth’s rotation is beneath and created by..?

Answer 3

Beneath two bulges (crust and ocean) created by gravitational force of sun and moon

Question 4

How does the moon’s alignment influence tides?

Answer 4

Shape of bubble changes with orientation between sun and moon
Aligned - spring tides (stronger when in middle of earth and sun
Quarterly and competing - neap tides - weaker pull

Question 5

What is the result of moon’s alignment on tides?

Answer 5

2 high tides per day, but earth is tilted so equal highs at equator and unequal highs at higher latitudes - tidal timings not the same everywhere, continents in the way

Question 6

What is Newton’s first law in relation to the earth’s rotation?

Answer 6

All objects in motion stay in motion unless acyed upon by an outside force - earth is rotating body

Question 7

Which way does the earth rotate and which way is the coriolis deflected in each hemisphere?

Answer 7

Rotates W -> E
N hemisphere - anticlockwise - deflection to right
S hemisphere - clockwise - deflection to left

Question 8

What are amphidromes?

Answer 8

Tidal ranges = 0

Question 9

What are the the concepts that influence on tides within the earth?

Answer 9

Tilt, rotation and friction (especially in shallow water)

Question 10

What is a resonance?

Answer 10

every basin sloshes with specific frequency and shape of basin will affect how long wave takes - big basin, longer time

Question 11

What happens when the resonance with frequency of tidal sloshing are combined?

Answer 11

If additive then amplitude of motion (tide) will INCREASE

Question 12

How are depth and friction related?

Answer 12

Depth (the shallower, the more friction) and shape matter to friction

Question 13

What are tidal bores?

Answer 13

Tidal wave shoals so much it breaks

Question 14

Height of high tide in basin is a result of

Answer 14

Shoaling and convergence increase height

Friction may decrease height (reduces energy in wave)

Question 15

What are the tidal highs per day

Answer 15

Semi-diurnal - 2 unequal highs and lows
Diurnal - 1 high and low
Mixed - double highs

Question 16

Implications

Answer 16

1000 years ago, Bay of Fundy has lower tidal intensity - natural resonance/sedimentation with time?/ SLR?
Estuary shape (3D) matters