About the Puget Sound Institute

Introduction
Another type of estuary is formed by tectonic activity, exemplified by San Francisco Bay, where
the ground sank over time as a result of pressure at the junction of the San Andreas and
Hayward faults. San Francisco Bay averages 25 feet deep with a maximum depth of 100 feet.
A fourth type of estuary, the bar-built estuary, is characterized by offshore sandbars or barrier
islands built up from river deposits. The Outer Banks off the coast of North Carolina helps
contain water flowing in from several major rivers to form Albemarle Sound and the adjacent
Pamlico Sound, both shallow waterways.
The human factor
Puget Sound’s complex estuarine character is also part of what makes it fragile. Close ties with
the land mean that it has had a long and, over the past 100 years, increasingly fraught
relationship with humans. Conditions in Puget Sound have changed greatly since Capt. George
Vancouver explored the inland waterway, reporting back to England that the area was suitable
for settlement. Even the name “Puget Sound” has changed its meaning.
When Vancouver’s ship Discovery stopped at the south end of Bainbridge Island in May 1792,
Vancouver sent Lt. Peter Puget and a crew in two small boats to explore every branching inlet to
the south.
In 10 days, the work was done and the carefully prepared charts were handed over to Vancouver,
who later declared, “by our joint
efforts, we had completely explored
every turning of this extensive
inlet.” He added, “To
commemorate Mr. Puget’s
exertions, the south extremity of it
I named ‘Puget’s Sound.’”
Because of this, the original Puget
Sound covered just the waterway
south of the Tacoma Narrows to
Olympia. Later, after the name
came into wider usage, the U.S.
Board on Geographical Names
placed the boundary of Puget
Sound just inside the Strait of Juan
de Fuca.
Puget Sound is also recognized as
part of the Salish Sea, a vast
interconnected estuary that
stretches out 6,535 miles and
Water circulation
Water circulation—the net result of tides,
winds and streamflows—varies from place to
place in Puget Sound, playing a direct role in
habitat formation and productivity.
Freshwater, being less dense than seawater,
tends to float in a surface layer that generally
moves toward the ocean. Meanwhile, a deep
layer of heavy seawater from the ocean pushes
into Puget Sound along the bottom. Both
layers ebb and flood with the vigorous tides
that drive Puget Sound water movements.
Strong winds and underwater formations,
including the sills at Admiralty Inlet and
Tacoma Narrows, interact with the tides to
facilitate mixing between the layers, making
nutrients available for phytoplankton.
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