Whidbey Island is a great place to see deposits of several lowland Pleistocene glacial and interglacial sequences, combined with very pleasant beach walks. These field trips are ideal for winter. It is best to go near the start of an ebb tide- don’t get trapped against a steep cliff of sand and gravel by the flood tide! Use your head and consult tide charts. I’m including UTM grid coordinates for selected places, using the NAD 27 coordinate system. You don’t need them to find your way around, but a number of folks have asked for them on these field trips.
| Late-Pleistocene glacial sequence at Whidbey Island | Age: 14C or thermoluminescence | Whidbey field trip | ||
| Fraser Glaciation | Everson gmd | 10,370-13,010 | Blowers Bluff; West Beach* | |
| Vashon till | ~15,000 | West Beach | ||
| Esperance sand (outwash) | 18,000 | Blowers Bluff | ||
| Olympia Interglacial | fluvial, lacustrine, peat deposits | 22-28,000 | Blower’s Bluff | |
| Possession Glaciation | glaciomarine drift | 70,000 | Blower’s Bluff | |
| till | Blower’s Bluff | |||
| outwash | ||||
| Whidbey Interglacial | fluvial, lacustrine, peat deposits | ~100-150,000 | Double Bluff, Blowers Bluff | |
| Double Bluff Glaciation | Double Bluff gmd | 175- 200,000 | Double Bluff | |
| Double Bluff till | ||||
| outwash | ||||
* location not yet visited or written for Northwest Geology Field Trips website.
The trips that comprise this series of field trips will each have there own pages. Click the link to go to each trip.
The first trip visits the lowest sequence of Pleistocene glacial and interglacial sediments on Whidbey, the Double Bluff glaciation and the Whidbey interglacial period which followed.
Part 1: Useless Bay and Double Bluff- Pleistocene strata & earthquake-deformed interglacial sediment
Part 2: Blowers Bluff- Latest Pleistocene glacial and interglacial sediments
Hello
I own a home on the sand cliff on west beach road, on whidbey island, and am interested in learning more about its geological history, stability and past landslides. There have been several landslides on this cliff in the distant past, and I’d like to learn more about them. I’m also interested in knowing more about the fossils likely to be found in the strata of this cliff.
Regards,
FrankH
Frank,
Essentially the entire shoreline of Whidbey Island south of the Deception Pass area is glacial and interglacial deposits. These are inherently unstable. Erosion has created the current shape of the island, as the sea has been gradually whittling away at these bluffs ever since the last ice retreated. It is conceivable to me that someday the entire island could be a thing of the past, though we are talking tens of thousands of years. Rising sea levels would likely increase the erosion rates, as well. There have been many fossil finds in the Whidbey sea bluffs; all are Pleistocene and Holocene animals that roamed the area between glacial advances, or since the last one- mammoths, bears, and the like. There are fossil mammoth tusks and a large bear skull from Whidbey on display in the WWU geology department’s halls.
I’ll describe that collection in the guide book to Western Washington geology that I’m currently writing for interested laypeople about.
Dave
Dave