coastal, beaches, estuaries Flashcards
explain what coasts are
where land meets the sea
Area affected by marine processes
- tides, wind, waves, storm surges
➢ Dynamic places of constant change
- deposition and erosion of sediments
what are some examples of coasts
cliffs dunes, beaches, bays, coves and river deltas
what is a primary coast
where coasts are shaped by processes on land, sediment erosion or deposition by rivers wind and ice.
what are the two main causes of primary coasts?
VOLCANIC ACTIVITY: Hawaii lava builds up, the tectonic plates move, and repeats this series repeats (left most island =oldest right most island=youngest)
SEISMIC ACTIVITY: San Francisco Bay or Tomales Bay; where tectonic movement causes a faulting and displacement of the earths crust.
another example: drowned river valley
what is a secondary coast
Where the ocean changes the coast
-waves, tides, current
- Alterations by marine plants
what’s an example of secondary coasts
-White cliffs of dover. Made of foraminifera shells. The cliff was once under water but sea level fell and the cliff was eroded by waves.
-Sea Stacks by wave erosion
-Barrier Islands- a sediment source is carved out and deposited else where .
-Mangroves, salt marshes- coastal vegetation- very productive areas - formed by intrusion of sea water.
what is a delta ?
deposit of river-borne sediment left at a river mouth
- produces a flat and fertile coastal area
what are the shapes and structures of beaches?
wide or narrow
steep or flat
long or pocket
what sources create beaches ?
land materials brought by rivers or derived
from local cliffs by wave erosion
- shell, coral, minerals, rock particles, and lava
what kind of beach has high energy and why
steep or flat
STEEP!
what kind of beach has higher energy and why?
[sand+mud ]or [pebble cobble and boulder ]
PEBBLE COBBLE AND BOULDER. found close to their source, too
large to be moved any distance
why are sand an bus beaches lower energy ?
eroded materials, small particles easily
transported or redistributed by waves and currents
High energy beaches have ___ sand and low energy beaches have ____ sand
coarser: finer
color of beach sand is an indicator of :
what minerals the sand is made out of.
is beach sand in constant motion ?
yes
there is dynamic equilibrium between supply, transport and removal of sediment. what are the two beach dynamics we learned in class?
alongshore transport and split formation.
explain alongshore transport.
Alongshore transport moves sediment along the coast in a zigzag pattern due to angled wave action.
waves approach, gravity pull them down, water moves, repeat
explain split formation.
occurs when sediment transported by alongshore currents is deposited in an area where wave energy decreases, extending the shoreline out into the water.
what are estuaries
where the river meets the ocean
if a split formation closes what do we cal this
a coastal lagoon
if a split formation reaches out to an island we call this a
tombolo
what are some for characteristics of an estuary
Sources of buoyant water plumes
*heavily populated
* Are habitats for a large number of
organisms
* Formed as a result of sea level rise
* Very young (10,000 years) in
geological terms
* Have global significance due to their
capacity to exchange water and
sediment with the ocean
classification of estuaries by tide :
microtidal <2m
* mesotidal 2-4 m
* macrotidal 4-6 m
* hypertidal >6
classification of estuary by topography
Drowned river valleys (Coastal
Plain Estuaries)
* Formed by rising sea level
* Fjords
* Formed by retreating
glaciers
classification of estuary by salinity
highly stratified
* salt wedge estuary
– well mixed estuary
– partially mixed estuary
explain the characteristic of a salt wedge estuary
High river discharge
* Weak tidal currents
* Strong stratification
* Weak mixing
explain characteristics of a well mixed estuary
Low river discharge
* Strong tidal currents
* Weak stratification
* Strong mixing
explain the characteristics of a partially mixed estuary
Mixture of salt-wedge and well-mixed
* Most prevalent estuary
what are some key characteristics of river deltas
Extensive agricultural
development
* Highly populated
1) High sediment load
2) Low energy waves and currents at the river mouth
