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Sea-Floor Sunday #40: Puyallup Delta, Puget Sound

January 25, 2009

I apologize for the lack of posts lately … I have been incredibly busy the last month or so. On top of my day job and trying to finish manuscripts, I’m also heading back down to Patagonia in a few weeks to co-convene and lead a research conference. We are really excited about the mix of researchers that are coming to the conference. I will certainly post about the conference and share photographs when I return.

Anyway … here’s a real quick Sea-Floor Sunday image. The USGS Seafloor Mapping program is a great source for sea-floor topographic (bathymetric) images and data. The image below is from the Puyallup river delta in Puget Sound, Washington (click on the images or here to go to the page on USGS’ site).

USGS)

Color shaded-relief bathymetry of Puyallup Delta, offshore Tacoma Washington (credit: USGS)

As a sedimentary geologist, what I find most interesting are the features coming right off the delta and down onto the delta front in deeper water. This perspective image below is about a kilometer across and shows a couple interesting features.

USGS)

Perspective view of Puyallup delta front, Puget Sound (credit: USGS)

The area marked with the ‘A’ is a channel feature coming directly from the river mouth (note the bedforms) and ‘B’ is showing some failure scarps on an oversteepened part of the delta slope.

If you go to the USGS site they also show a comparison of this newer, higher-resolution data with the legacy data of the ’70s/’80s — the difference is amazing.

To learn even more about the sedimentary features and processes of the Puyallup delta, check out this paper:

Mitchell, N., 2005, Channelized erosion through a marine dump site of dredge spoils at the mouth of the Puyallup River, Washington State, USA: Marine Geology, v. 220, p. 131-151.

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4 Comments leave one →
  1. Mark Sitton permalink
    January 27, 2009 3:35 pm

    Wow, I really like the prospective view in this. Was this created in ArcGIS, do you know?

  2. January 27, 2009 3:41 pm

    Mark, no I don’t know … it doesn’t say anywhere on that webpage or in the open file report.

  3. January 28, 2009 2:24 am

    How big a tsunami would one of those slope failures push up into downtown?

  4. January 28, 2009 6:38 am

    Lab Lemming … just off the top of my head (no real calculations or research) I would guess that the small delta-front failures wouldn’t do too much. But, if the *entire* delta-front slid away …

    Would probably take a >7.0 eq to do that … the ‘normal’ mass wasting probably wouldn’t generate a huge tsunami.

    But, I don’t know for sure … would have to do some research.

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