Students from the UW MeSSAGE program log a core pulled from the Discovery Bay salt marsh
Discovery Bay on the Strait of Juan de Fuca in Washington State is one of the most important sites in this area from a coastal hazards standpoint. Why? Because written in the sediments of the salt marsh at the head of the bay is a record of multiple tsunamis, that are manifested as sand layers sandwiched between layers of peat:
Tsunami sand layer in the bank of Salmon Creek, which cuts through the salt marsh at the head of Discovery Bay
I've visited the Discovery Bay marsh on multiple occasions, and written in more detail about the background of the site and tsunami risk in Washington State in general. On 20 June 2014, though, I had my first opportunity to go out, in partnership with students and faculty from the UW MeSSAGE Program, Carrie Garrison-Laney (a graduate student at UW), and Ron Tognazzini (a retired earthquake engineer) and actually collect some data at the marsh in an effort to better understand the site and how it has been impacted by tsunamis.
Carrie Garrison-Laney, a UW graduate student focused on tsunami sedimentology, talks to a group of students from the UW MeSSAGE Program after the field day.
Having that many people on the marsh allowed us to really spread out and core a variety of sites around the marsh:
Core sites in the Discovery Bay marsh on 20 June 2014
At each sites students pulled cores of the marsh - in some cases the cores were 3 meters long - and then painstakingly described the stratigraphy of each core in terms of grain size and sedimentology. Additionally, a few samples were collected for carbon-14 analysis. The goal - improve our understanding of the dates of events recorded in the sediment, and also potentially understand something about the dynamics of events by trying to connect layers across the entire marsh.
A coring team at work
A potential tsunami layer exposed in the core barrel after being pulled from the marsh
