Transcript Currents and Waves - Pleasant Grove Middle School

Currents and Waves
Surface Currents
• Ocean Circulation
Patterns
– Winds are the primary
driving force
– Relationship between
oceanic circulation and
atmospheric
circulation
Surface Currents
– Coriolis effect
• Currents are
deflected due to the
Earth’s rotation
• To the right in the
Northern
Hemisphere
• To the left in the
Southern
Hemisphere
Surface Currents
• Ocean Currents and
Upwelling
– Upwelling
• Rising of cold water from
deeper layers to replace
warmer surface water—
vertical movement
• Brings up concentrated
nutrients
Surface Currents
• The Importance of Ocean Currents
– Affect time to reach a destination
– Affect climates—moderate temperatures
– Helps maintain Earth’s heat balance
Deep-Ocean Circulation
• Gravity and density differences
• Temperature and salinity create a dense
mass of water
– Thermohaline circulation
– Water is made colder and saltier at the
surface, becomes more dense, and sinks
– Arctic and Antarctic mainly affected
Tides
• Causes
– Gravity
– Bulge toward and away
from the moon
– Two high tides and two low
tides per day
– During new and full moons,
moon and sun affect tides
• Spring tide—higher crests
and lower troughs
– During 1st and 3rd quarters
of the moon
• Neap tide—daily tidal range
is less
Tides
• Types of Tides
– Semidiurnal
• Twice daily
– Diurnal
• Single high and low water height each day
– Mixed
• Inequality of tides
Tides
• Tidal Currents
– Horizontal flow of water accompanying the
rise and fall of the tide
– Flood currents
• Advance into the coastal zone as the tide rises
– Ebb currents
• Water retreats during low tide
– Slack water
• Between flood and ebb
Tides
– Tidal flats
• Areas affected by flood and ebb currents
– Tidal deltas
• Deposits created by tidal currents
Waves Modify the Shoreline
• Characteristics of Waves
– Crest—top of a wave
– Trough—bottom of a wave
– Wave height—length
between crest and trough
– Wavelength—length
between two crests
– Wave period—time
interval between
successive crests
Waves Modify the Shoreline
• Types of Waves
– Energy
• Move through the nearly stationary medium of the
water
– Oscillation
• Waves in the open sea
– Translation
• Water advances up the shore because of a break
Wave Erosion
• Pressure from waves
can exceed 2000
lb/ft2
• Causes air in cracks
to compress and then
expand as the wave
recedes
• Abrasion
– Sawing and grinding of
water with rock
fragments
Wave Refraction
• Bending of waves
• Affects distribution of
energy
• Influences erosion,
sediment transport,
and deposition