15,000 years ago the lake and swamp were covered by the Vashon ice sheet – a
glacier that came down through the Puget Sound. As it receded, it left behind
many of the hills that run north-south in Seattle, and left behind what is now
Lake Washington. The way in which the lake and the swamp formed made the swamp
a particularly interesting place because of the peat soil that it has. Peat
soil is at Yesler Swamp because peat forms over many years when vegetation
decomposes very slowly due to water (in this case from the lake) covering the
vegetation which lets less atmospheric oxygen to the vegetation. This kind of
soil is common only in very wet places like wetlands, swamps, and bogs. Luckily
for Yesler Swamp, peat isn’t very good to build on because of how loose and wet
it is, which is the reason that after the sawmills burned down the swamp was
left alone while everything around it developed. Without the peat, there may
have been another house built on this unique plot of land.
Another interesting thing to note is that the water level
of the lake changes about 2 feet from season to season. The Hiram Chittenden
locks that connect Lake Union to the Puget Sound regulate the water level of
the lakes, and typically keep the water level in the lakes lower in the winter
for better storm protection for houses perhaps. In the winter it is very easy
to see the pilings from the old saw mill sticking up out of the water, and you
can even walk further out into the inlet of the lake than you can in the
summer. It is interesting to think about all the ways in which a change like
this may affect animals and plants using the shorelines along places like
Yesler Swamp.
This work could not have been done without the help of:
http://www.nws.usace.army.mil/Missions/CivilWorks/LocksandDams/ChittendenLocks.aspx
No comments:
Post a Comment