Waves,Tides & Currents
#Waves
> A disturbance which moves through or
over the surface of a
fluid.
> Mostly caused by winds
(Also earthquakes, volcanoes, grav. pull)
#What Causes Tides?
1. Gravitational pull of
sun & moon on Earth
• Moon closer, therefore
> effect
• Like magnet, pulls
water away from
surface = TIDAL BULGE
2. Centrifugal Forces
• Produced by motions of
Earth, sun, & moon
• Bulge on opposite side
because centr. force
> pull of moon
>Form of great energy.
#Water Motion in Waves
1. Water travels in vertical
circular orbits
2. Wave moves, particles don’t!
#Size of Wind Generated
Waves
> Depends on 3 things:
★ Wind Speed
★ Wind Duration (length of time wind blows)
★“Fetch” Extent of open water across which the wind can blow.
Types of Waves
1. CHOP – Short period
2. SWELL – Long period (boat rolls; seasickness)
3. SWASH – water up beach
4. BACKWASH – back down
Tides
* The rhythmic rise and fall of the ocean’s water
High tide = rising,
incoming tide, flow
Low tide = receding,
outgoing tide, ebb
Slack tide = vertical
movement stops
#What Causes Tides?
1. Gravitational pull of
sun & moon on Earth
• Moon closer, therefore
> effect
• Like magnet, pulls
water away from
surface = TIDAL BULGE
2. Centrifugal Forces
• Produced by motions of
Earth, sun, & moon
• Bulge on opposite side
because centr. force
> pull of moon
Types of Tides
•Spring Tide
– Moon and sun are in direct line with one another
– Results in unusually high tidal range
-Tidal Range = vertical
distance between high & low tides
Types of Tides
•2x’s/month
*Neap Tide
– sun and moon are at
right angles
-Pulls cancel each
other out – causes a
weak pull
– unusually low tidal
range
2 x’s / month
#Currents
• What are currents?
– Circulation water
• Causes
– Wind
– Rotating Earth
– Density Changes
RIP CURRENT
– Caused by converging long-shore currents
– Very dangerous ; Red Flag – DO NOT fight rip current; swim parallel to shore to get out of channel.
Deep Ocean Currents
(The Global Conveyor Belt – Currents)
Separated from surface currents by boundary called a “Thermohaline” (diff in densities).
Flow beneath surface; cross equator.
Move North to South.