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Quiz – 5 minutes: Separate Paper. In which of the following would you most likely find commercially usable reservoirs of oil or deposits of sand and gravel? A) Continental Shelf B) Continental Slope C) Continental Rise 2. Which of the following sediments precipitates directly from seawater? - PowerPoint PPT Presentation
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Quiz – 5 minutes: Separate Paper1. In which of the following would you most likely find
commercially usable reservoirs of oil or deposits of sand and gravel?A) Continental Shelf
B) Continental Slope C) Continental Rise
2. Which of the following sediments precipitates directly from seawater?A) TerrigenousB) BiogenousC) Hydrogenous
3. Compare and contrast the Pacific and Atlantic continental margins.
Puget Sound Seafloor
Chapter 14 vs. Puget Sound
• In general, the features described in Chapter 14 are not found in Puget Sound (no mid-ocean ridges, cont’l shelf, slope, rise, seamount, guyot, trench, atoll…)
• Instead, Puget Sound’s seafloor consists of sediments shaped by recent (<25,000 years before present) glacial action
Glaciers
Energy and Movement of Material
Water can provide a “low to high energy” environment and is capable of moving clay, sand, gravel and boulders
Air is generally “low energy” and is capable of moving clay and sand
Glaciers…
Glaciers can be “extreme energy” and move clay, sand, boulders, and house-sized boulders
Glacial “Erratic”
How Erratics Can be “Plucked” and Transported
Glacial Scouring
• Video• http://exhibits.pacsci.org/puget_sound/graphi
cs/ps_glaciationsm.mov
So, What’s Beneath the Surface?
Puget Sound “Scoured Out” by Glaciers
Red = ShallowBlue = Deep
Puget Sound “Scoured Out” by Glaciers
Red = ShallowBlue = Deep
Deep basins
Shallow Sills
Profile View of Previous SlideNorth South
Shallow Sills
Deep basins
Video Again
http://exhibits.pacsci.org/puget_sound/graphics/ps_glaciationsm.mov
Interesting Aside (Not Oceanography)
Glacial Deposits•Layered clay accumulates in the bottoms of large, pro-glacial (“in front of the glacier”) lakes
•Layered sand and gravel accumulates in the bottoms of rivers draining the lake (called “outwash”)
•“Glacial till” deposited directly by the glacier: very dense, non-layered mixture of clay to house-sized boulders
Glacial Deposits“Lacustrine” (lake) clay
Clay
Glacial Deposits
“Outwash” sand and gravel
Glacial Till
Interesting Aside (not oceanography)
Summary of Puget Sound Glaciation
1.“Old,” pre-glacial sediments (hard sands, clays etc.) on bottom2.Pro-glacial lake deposited clay next3.Advancing glacier deposited “outwash” (sand and gravel) next4.Glacier deposited till next5.Glacier receded, scouring the landscape and depositing the opposite sequence6.Left behind Puget Sound, which filled with ocean water
Landslide Situations
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