Lecture 16: Oceans 2 Flashcards
Why do Waves occur?
Due to the effects of wind acting on the surface of the ocean
What is the movement of waves?
Looping orbitals in which motion decreases downward to the wave base
How does Shallow water effect waves?
Wave orbitals flatten in shallow water because of drag
What is Wave Refraction?
When waves become more parallel to seafloor contours (and the shore) as the wave encountours the sea floor
What is Longshore drift?
When waves approach the shore obliquely and undergo refraction and the oscillating motion of water is converted to a longshore current
What is Longshore Drift?
When sediments are carried along the shore during longshore drift? lol
What are Tides?
Rise and fall of the level of the ocean at coastlines twice per day due to gravitation interactions between the earth with the moon and sun
Which body is more important to do with tides?
The moon
Which two bodies have a common center of gravity and where is it located?
The earth and the moon and it is in the earth because the earth has more mass
Why is water pulled toward the moon?
Because the moon’s gravity on the earth’s side is stronger than necessary to maintain orbit. This is why water on the far side pulls away from the moon
What shape is the Hydrosphere pulled into?
An ellipsoid shape
How often do High tides occur?
Twice every 24 hours and 50 minutes
How is tide perceived in shallow water?
Tide is amplified so it is more dramatic than in the ocean
What are Spring tides?
When the sun and moon are in line with the earth and create the seasonally extreme tides: The highest high tides and the lowest low tides
What are Neap Tides?
When the sun and moon are at 90º to each other with respect to the earth and the gravitational effects of the sun and the moon partially cancel out and the tides that occur are the mildest of the year
What are Eustatic changes?
Changes that result from a combination of worldwide sea-level change
What do Eustatic changes result from?
Changes in climate
How is Ice related to Eustatic sea changes?
During climate change ice forms and reduces the level of water reducing global sea levels
How do Tectonic plates affect Eustatic change?
They change the ocean basins which directly impact sea level
What can cause local changes to sea level?
- Tectonic plate movements
- Isostatic responses to ice sheets and ice caps
- Compaction of sediments
What is Isostatic depression and post-glacial rebound?
When ice melts or glaciers move causing regional differences in tide due to the rebounding of the mantle
Where can Ocean sediments be deposited?
In oceans near to the coast, on the continental shelf, or in the deep ocean
In what way can ocean sediments be deposited on the coast?
Via deltas, estuaries and beaches
What are deep ocean sediments known as?
Pelagic sediments
What does the Benthic Zone refer to?
The bottom of the ocean and the organisms that live there
What is the Pelagic zone?
The water column
What can the Pelagic zone be divided by?
Depth
What is the Photic zone?
The top 200 meters where sunlight reaches
What is the Aphotic zone?
The area below the Photic zone
What is the Littoral Zone?
The thin region near to the shore that experiences tides
Where does the Neritic zone span?
The position of low tide to the continental shelf slope
What is the Oceanic zone?
The zone beyond the shelf
Where do Deltas form and what are they?
In areas where a river enters into the sea and the erosional action of waves and currents in not great enough to remove all of the sediment being transported by a river causing sediment to pile and build up
What are Estuaries?
Semi-enclosed embayments that are fed by freshwater from one or more rivers
What are the characteristics of Estuaries?
Rapid change in water salinity
Significant sediment deposition may occur
Hosts a great variety of plant and animal life
What are Beaches?
Accumulations of well sorted sediment that lie at the edge of water bodies such as oceans
Where may sediment from beaches arise?
Weathering and erosion of adjacent rock or from sediment transported to the oceans from river
What causes more sediment on beaches?
Weaker wave like action
What are Continental shelves?
Large areas that are part of the continent where depth below sea level is greater than 200m and are covered with clastic sediment (sand and mud) or carbonate sediment
What are Carbonate Shorlines?
When organisms build reefs, structures of calcium carbonate and build them up from the sea floor producing atolls around former volcanic islands
What are Pelagic sediments?
Sediments that cover the deep ocean and are primarily composed of pelagic clay and pelagic ooze
What is Pelagic ooze?
The shells of microscopic organisms
How do Turbidites form?
Avalanches underwater of pelagic sediment that falls at the continental slope
What are Carbonate shells more susceptible to?
Dissolution before deposition but carbonate oozes are more common
