Tides Flashcards
What is the tides regular cycle?
24h 50m
What is the ebb tide?
The tide is going out. High to low tide
What is the flood tide?
The tide is coming in. Low tide to high tide
What causes tides?
Gravitational attraction
What is the ratio of attraction between the moon and sun?
11 : 5
Moon : sun
How do you calculate gravitational attraction?
F = G Mm / R2
Earths diameter - 13,000 km
What are the types of tide?
Semidiurnal - 2H 2L
Diurnal - 1H 1L
Mixed tides - unequal tides
What is a spring tide?
New and full moon
Sun and moon pull in the same direction creating a larger bulge
What is a neap tide?
First and last quarter moon
Sun and moon pull perpendicular creating a smaller bulge
What are tidal streams?
Open ocean they are less noticeable
Constrained by geomorphology
How do you measure tides?
Using a stilling well along the coastline
Filters out wave motion
Tides and changes in sea level are measures relative to a permanent level benchmark
What are the principle tide raising constituents?
M2 - semi diurnal tide raising force of the mean moon
S2 - semi diurnal tide raising force of the mean sun
K1 - diurnal Luni-solar declination
O1 - diurnal lunar declination
What are land maps?
Elevations established relative to height above mean sea level (Geoid)
What is Ordnance datum Newlyn measured against?
Average sea level
What are admiralty charts?
Display bathymetry and used for navigation
