ESS/OCEAN 230 (Rivers & Beaches)
Mid-term Exam, Fall 2007
What is your name?________________
Questions to be answered by a few words
What are the very deepest features in the ocean, and on what type of continental margins do
they form (4 pts)?
Most Puget Sound rivers have two peaks in discharge each year. When do they occur and
what processes cause each of these peaks (4 pts)?
What are the typical salinity values of ocean water and of river water (2 pts)?
What is another common name for a bar-built estuary (2 pts).
Rivers supply billions of tons sand and mud to the ocean each year. What approximate
percentage of each is supplied by typical rivers (2 pts)?
Questions to be answered by a few sentences (5 points each)
Plate tectonics is a mechanism that moves continental and oceanic crust. Briefly explain
what happens when a continental plate collides with an oceanic plate.
Describe the history of continental shelves during the past 20,000 years.
The largest canyons on Earth are found below sea level. Describe the processes that erode
the sea floor to form these submarine canyons.
Biogenic sediments are common on the ocean floor away from continental margins.
Describe the source of these materials and their most common composition.
Lithogenic sediments are the dominant material filling ocean basins. Explain what
mechanisms transport lithogenic sediment to the ocean.
Puget Sound is composed of a sinuous complex of depressions, which are now filled with sea
water. Briefly explain what processes created Puget Sound.
Coastal-plain estuaries are excellent traps for sediment due to “estuarine” circulation and
particle flocculation. Explain how these processes conspire to trap sediment.
The surfaces of deltas undergo subsidence. A good example is the city of New Orleans,
which sits on the Mississippi delta and has subsided tens of feet below sea level. Explain
why the surfaces of deltas subside below sea level.
The mouth of the Nisqually River is building seaward into Puget Sound as a delta. The
topset and foreset regions of the delta are important part of this delta. Explain how these
regions are related to delta growth.