CH 16 The Dynamic Ocean
 Ocean water is in constant motion and powered by
many forces
Forces include wind, Coriolis, gravity, density differences
 Ocean currents are masses of ocean water that flow
from one place to another
Surface or deep
Surface Currents
 Movements of water that flow horizontally
 Develop from wind friction
 Gyres = huge circular moving current systems (5)
 Coriolis Effect = the deflection of currents to the right
in the NH (& left in the SH) due to earth’s rotation
 Warm currents move from the equator to the poles
 Cold currents move from polar regions to the equator
 Cold currents = west coast; warm currents = east coast
Deep Ocean Circulation
 Vertical movement of water
 Upwelling = cold water rising from deep layers to
replace warm surface water
Brings nutrients to surface(good for fishing)
 Density currents = vertical currents of water due to
density differences
From temperature(cold) and salinity (high)
Read pages 451 – 453
Waves
 Most waves obtain their energy and motion from wind
 Big wind = big waves
 Crest = top
 Trough = bottom
 Wave height = distance from trough up to crest
 Wavelength = distance from crest to next crest
 Wave period = time it takes a full wavelength to pass a
fixed position
 Height, length, & period of waves depends on 3
factors:
1. Wind speed
2. Length of time the wind blows
3. Fetch (distance across body of water)
The only thing that really moves forward in a wave is
energy(particles move in circular orbital motion)
Breakers--Waves that break (fall forward) when the
depth of the water is one-half of the wavelength.
TIDES
Please see other PP
SHORELINE PROCESSES/FEATURES
 BEACH = accumulation of sediment along
shores. (white,pink,tan,black,green)
 SHORELINE (WAVE) FORCES:
Eroding
Transporting
Depositing
Wave impact
Abrasion
Refraction = bending of waves
 Wave energy is concentrated at headlands =
more erosion
 Wave energy is weakened in bays = more
deposition
 Longshore current = sediments carried along
(parallel) to shore due to waves hitting at an
angle.
EROSIONAL FEATURES:
 Sea Cliff – result from waves cutting at the base
 Sea Cave – from softer rock being eroded
 Sea Arch – cave all the way through
 Sea Stacks – roof of the arch collapses
 Wave-cut platform or terrace – from continued
wave action causing a flat eroded area
DEPOSITIONAL FEATURES:
 Spit – elongated ridge of sand sticking into the
bay
 Hook – when the spit hooks due to currents
 Baymouth Bar – when a sand bar completely
crosses the bay
 Tombolo – a ridge of sand that connects an
island to the mainland
 Barrier Islands = (Outer Banks)
Stabilizing/protecting shores:
 Jetties or groins –barrier built at right angles to
the beach to catch sand
 Breakwaters – offshore and parallel to coast
 Seawalls – parallel to coast often from the shore
 Beach nourishments
 Natural protectors:
sand bars, sand dunes,
fringing reefs, barrier reefs, & atolls