The field trip to Discovery Park was useful in conducting a geological study on the four layers of sediment that describe the physical history of the Puget Sound. Just by looking at the sediment the four layers tell an interesting story of how the Puget Sound was formed. 35,000 years ago the Puget Sound was flat land with rivers flowing through it, this started the first of the four layers. The oldest layer of the four is called the Olympia Formation, it is 35,000 years old and was deposited by rivers before a glacier came and blocked the rivers and made the Puget Sound into a large lake. The Olympia Formation is know to contain ripples and has iron oxides in the sediment which explains why it is a reddish brown color. The second oldest layer is called the Lawton Formation; it is made up of clay that was formed by slow moving water, like the lake that the glacier created.
The clay is very well sorted, but also contains drop stones that were deposited by the glacier. The second youngest layer is called the Esperance Formation and was deposited as glacial outwash sediment. The cross bedding in the sediment indicates that water once flowed in a southern direction. The sediment is fine-grained indicating a fast moving or high-energy body of water. The youngest layer is called the Vashon Formation and unlike the other layers it is poorly sorted, this was due to the glacier moving over the Puget Sound and depositing glacial till.