tides lecture part one
DESCRIPTION
Part one of the Tides notesTRANSCRIPT
Tides
Description of tides
tides - periodic rise and fall of ocean waters
Main Factor #1: Gravitational pull of the moon and sun
Main Factor #2: Centripetal force of the rotating Earth
Tides are caused by:
Main Factor #1: Gravitational Pull
the gravitational pull of the moon and sun
sun
earth
moon
The force of gravity depends on...
Main Factor #1: Gravitational Pull
Gravitational Force
earth moon
The earth-moon system revolves around the barycenter.
Main Factor #2: Centripetal and Centrifugal Forces
CENTRIPETAL
GRAVITATIONAL FORCE
GRAVITATIONAL & CENTRIPETAL
Main Factor #2: Centripetal and Centrifugal Forces
GRAVITATIONAL & CENTRIPETAL
Tidal Patterns
Semidiurnal tides- two high and two low per day; Cape Cod, MA (high latitudes)
Diurnal tides- one high and one low per day; Mobile, AL (low latitudes)
Mixed pattern tides- Two high and two low tides per day BUT with successive high tide levels that are VERY DIFFERENT from each other; Hawaii (mid latitudes)
Tidal Patterns
Type of tide depends on:Position on the globeWater depthContour- shape of ocean basinsgeography of coastlines
How do Tides Vary?
A tidal range is the difference between levels of ocean water at high tide and low tide. The combined forces of the sun and the moon on Earth produce different tidal ranges.
The Bay of Fundy: Site of the world’s largest tidal range
Tidal energy is focused by shape and shallowness of bayMaximum spring tidal range in Minas Basin = 17 meters (56 feet)
Bay of Fundy
High tide
Low tide(6 hours later)
Nova Scotia Tides
Wolfville, NS (16 m tidal range)Diurnal Tides (one high and one low every 12 hours and 25 minutes
Timing the Tides
The moon revolves around Earth much more slowly than Earth rotates.High and low tides at that place happen 50 min. later each day.
By the time the Earth has completed one revolution (one day), the moon has moved slightly, so the Earth needs to rotate a bit more to catch up with the moon…
Diurnal Tide: 24 hr 50 min cycleSemi Diurnal Tide: 12 hr 25 min cycleMixed Tide: 12 hr 25 min cycle
Tidal Cycles
Explain to your neighbor
A: Why are there two tides on both sides of the Earth?
B: Explain why tides do not occur at the same time each day.
