Quiz – 5 minutes: Separate Paper
1. 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) Terrigenous
B) Biogenous
C) 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 midocean 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 housesized 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 = Shallow
Blue = Deep
Puget Sound “Scoured Out” by
Glaciers
Red = Shallow
Blue = Deep
Shallow
Sills
Deep basins
North
Profile View of Previous Slide
South
Deep
basins
Shallow
Sills
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, proglacial (“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
Outwash
Glacial Till
Interesting Aside (not oceanography)
Summary of Puget Sound Glaciation
1.“Old,” pre-glacial sediments (hard sands, clays etc.) on
bottom
2.Pro-glacial lake deposited clay next
3.Advancing glacier deposited “outwash” (sand and
gravel) next
4.Glacier deposited till next
5.Glacier receded, scouring the landscape and depositing
the opposite sequence
6.Left behind Puget Sound, which filled with ocean water
Landslide Situations