Transcript PowerPoint file

Chapter 12: Coasts
Classification (difficult task)
tectonics
active
passive
sea-level change
may vary widely
causes
global (eustatic)
 from +6m to -125 m in the last 2 MY
 volume of water available (can be tied up in ice)
 capacity of ocean basins (can be reduced by faster seafloor spreading)
 volume changes due to temp changes
local
 tectonics
 isostacy
Primary Coasts
characterisitics
young
usually shaped by terrestrial processes
sea level change exposes new areas to erosion
heavy deposition extends the land into the sea
Primary coasts
cut by land erosion, then flooded by sea-level
rise
drowned river valleys
fjords
cut by wave erosion, then sea-level falls
wave-cut terraces
built out by land processes
river deltas - fig p 294
moraines
volcanic
earth movement
upward
downward
Secondary Coasts
old
shaped by waves
Secondary Coasts:
Wave Erosion
methods
abrasion
hydraulic pressure
dissolution
effects
sea cliffs
sea caves
sea stacks and arches
wave-cut platform
shore straightening
caused by wave refraction
waves focus on headlands
Secondary Coasts:
Beaches
 deposits that accumulate in low energy areas
 sand is always being moved
 profile fig p 300
 backshore - cliffs, dunes, seawall
 berm crest
 foreshore - intertidal zone
 off shore - longshore trough and bar
 rip currents
 on-shore and off-shore
 seasonal
 big waves - sand moves off-shore
 small waves - sand moves back on-shore
 effect of sea walls
Secondary Coasts:
Transportation & Deposition
longshore drift
transportation
wave motion pushes in at an angle
gravity pulls straight out
sand moves along the shore
effects
sand moves in the direction of the predominant waves
barrier islands
spits, baymouth bars, & tombolos
effects of groins, piers, jetties, breakwaters
Secondary Coasts:
Transportation & Deposition
coastal cells
sand moves
entry point - cliffs, river, etc
longshore drift
exit point - submarine canyon
human structures (dams, groins, jetties, piers,
breakwaters) can block flow of sand
Other Types of Coasts
reefs
mangrove swamps
estuaries
Estuaries
types
characterisitics
salt-wedge
partially mixed
well mixed
fjord
reverse
drowned river mouths
fjords
bar-built (barrier
value
island lagoons)
productive
tectonic (grabens)
sheltered
brackish
nurseries for the
ocean
lagoons & wetlands