This week, I’ve been thinking about deep time and how it relates to the history of my neighborhood.
And, I finally made it to the map collection in the Suzzallo Library at the University of Washington. They have drawers full of maps of Seattle:
I was allowed to pull the maps out and put them on a light box and trace them.
Most of the maps I found were similar to the ones I looked at online last week. But then I found a map, created in 1991, of the geology of the neighborhood I live in.
This map was particularly interesting to me because geologic time, deep time, humbles me. As much as I’ve been enjoying learning about the recent history of my neighborhood (1854 to the present), I’m even more interested in the impossibly huge span of geologic time - that extends back far beyond the human scale - that lives in the landscape around me.
I learned that most of the land in my neighborhood is composed of Vashon till which was deposited during the Vashon Glaciation approximately 19,000 years ago. At that time, glaciers covered Seattle during the Pleistocene Ice Age. The till is composed of clay, silt, sand, cobbles and boulders.
There is a huge bolder not far from my house called the “Wedgwood Rock.” It’s a glacial erratic (or rock carried by glacial ice from one area and deposited in another). According to Wikipedia, it was “a landmark for Native Americans in what was once a dense forest.” The land around the rock was left undeveloped until the mid-1940’s when it became the residential neighborhood it is today.
Also, according to Wikipedia, many animals lived in Seattle and probably in my neighborhood during the Vashon Glaciation: Bison, Muskox, Grey wolves, Scimitar-toothed cat, American Lion, Saber-toothed cat, Short faced bear, Columbian mammoths, American mastodons, Jefferson’s Ground Sloths and Mazama pocket gophers.
The geologic map at the library, and subsequent research into the Vashon Glaciation, reminded me how much the land around me has changed over time; how many different kinds of animals have come and gone; and how (relatively) long people have made this neighborhood home.
Deep time reminds me that I am just a grain of sand in a sea of time.
This has been another busy week and I have been feeling a bit stuck on how to move forward in our collaboration, but I have managed a little exploration. One of the things I have been thinking about is the geologic history of the area where I currently live. Karey has been discussing this through the concept of deep time, which is also called geologic time. I have started to realize that this is something that I’m also exploring this concept in my own way. I have been thinking about the hydrology our watershed and how much it has been modified over the last ~150 years. My thoughts have been more about what has happened recently, but the reason I’m interested is that I believe there was something valuable here before, something that had taken many thousands of years to create.
So I started looking for the creeks that are mostly covered with city buildings now. Driving through the area, I couldn’t spot any remnants of the creek closest to downtown, but traveling a bit south, I came across segments of Gilbert Creek.
You can see the street and on the left-hand side of the photo, a storm drain and a long crack. I have found that this type of long crack across the road is a sign of what is happening under the road.
Here is Gilbert Creek flowing into a giant culvert under the road. You can’t see the surrounding homes and apartments. If you look closely you can see the size of the sediment in the stream. Where it is flowing slowly, there is a deeper pool and fine tan sediment settled on the bottle and closer to the culvert, a shallow area with ripples and small rocks, where the water speeds up is called a riffle.
And this is the creek and culvert from the other side. You can see a large amount of “rip-wrap” (the rocks place on the slope to stabilize the bank. On the left-hand side of the photo you can see were the creek has been undercutting and eroding the bank when flows are high. If you look closely, you can see the icicles that formed as water flowed out through the subsurface of the soil and down towards the stream. Further downstream you can see several large trees that have fallen into the creek as that side of the bank eroded.
I’m narrating these photos because they look a bit ordinary. This could be any of thousands of creeks across urbanized areas of the world, but to me, there is this connection to these different time scales and the processes that formed these creeks. So when I look at these photos of this ordinary landscape, they bring up all sorts of questions and wonderings.
I was just researching the basics of the geological history of Wisconsin, so I’m planning to read more about that this week. And hopefully that will spark some collaborative ideas.