1. GEOL 1033 (Lesson 32 & 36) ppt file 103-30
ESTUARIES
GEOL 1033
(Lesson 32 & 36)
ppt file

2. ESTUARIES, BAYS, & LAGOONS
Bays = a general term for a coastal embayment.
Estuary = a bay that is semi-enclosed, has fresh-water input from a river(s), & experiences tides.
Lagoon = semi-enclosed bay with little or no river input & reduced to essentially no tides.

3. ESTUARIES Estuaries have: Estuaries are young features
Tidal influences
Tidal flats
Salt marshes
Wave action
River influences (freshwater, sediment input, & nutrients)
Sediment accumulation is significant
Estuaries are young features
Because they tend to fill with sediments
They are said to be “sediment sinks”

4. ESTUARIES Distribution = common & worldwide Size = varies
Depth = varies from shallow (coastal plains) to deep (fjord)
biological significance:
highest productivity in the world!
nutrients from land runoff (rivers)
shallow enough for photosynthesis
well mixed by tides for good distribution of oxygen
home of many organisms (very diverse and abundant life)
“nursery” for many open ocean organisms, e. g., shrimp, many fish.
Processes
tides tend to be the dominant physical environmental factor
waves are locally important (especially in large estuaries with long fetches)
bioturbation by invertebrates tends to homogenize subtidal sediments
Sedimentation rates are significant
Duration = 100’s to 1000’s years, not tens of thousands to millions

5. ORIGIN OF MOST ESTUARIES

6. TECTONIC ESTUARIES
San Francisco Bay is formed by three major faults. This “structural” bay is the site of the cities of Oakland and San Francisco - a recipe for disaster!

7. FJORDS
Fjord type estuaries were carved by glaciers that flowed down valleys to the sea.

8. DROWNED VALLEYS
Coastal plain river valleys are drowned by rising sea levels, forming estuaries.

9. CONSTRUCTIONAL ESTUARIES
Formation of an estuary behind a spit, bar or barrier island

10. TYPES OF ESTUARIES a) stratified (isohalines almost horizontal)
b) well-mixed (isohalines nearly vertical)
c) partially mixed (isohalines oblique)

11. END OF FILE

12. GENERALIZED COASTAL ECOSYSTEM MODEL
RIVERS NUTRIENTS
SEA
SUNLIGHT
SEDIMENTS PRODUCERS
CONSUMERS
DECOMPOSERS