Sucia Island Trip

On Friday we will be heading to the Sucia Island group. What makes this group of islands interesting is their geology. From the web I got the following info “ENVIRONMENTAL FEATURES Physical features Sucia island’s geologic formations are stunning for both the casual visitor and the trained geologist. This horseshoe shaped island with long finger-like peninsulas and islands is a classic example of a formation called a plunging marine syncline (HUH?).

The rocks of the island were laid down in sedimentary layers over many millions of years. The oldest exposed rocks were carried to the area by a large river which drained the Canadian Rocky Mountains long before the Cascade Mountain Range appeared. Later a shallow marine sea formed and marine sands and mud were deposited, along with the marine invertebrate seashells which would become fossilized eventually exposed in the Fossil Bay area. Next the collision of the oceanic plate with the north American continental plate caused the Cascade Mountain Range to develop. Rivers draining from the new mountain range brought sand and gravel deposits to the area over many millions of years. It also caused the land which was to later become Sucia Island to fold, bend, and uplift into a horseshoe shape.

More recent geological events were Ice Age glaciations, the most recent occurring 12 to 15 thousand years ago. Ice covered the area to a depth of over three thousand feet. When the climate warmed and the glaciers retreated the land was left with a covering of glacial till (sand, gravel, and boulders) which were carried to the area by the ice. Marine waters invaded the area and Sucia Island was formed. Since the retreat of the glaciers wind and wave erosion has continually eaten away the island’s shoreline, creating wave-cut platforms and reefs, honeycomb formations and caverns. The long narrow bays of Fossil Bay, Snoring Bay, and Ewing Cove were formed due to erosion of softer layers of sedimentary deposits. ”

I’m not a geologist but have been to this area as recently as last week.  Last Friday I worked with botanists making plant collections from throughout the San Juans.  At Ewing Island in the Sucia group we saw numerous Heerman’s gulls.  These are one of the few gulls that disperses north after breeding in California and Baja.

Heermann's gulls

One of our resident alcids is the pigeon guillemot and there is a large nesting colony in the Sucia/Matia area.  The attached photos were taken in late May.

.pigeon guillemot Pigeon guillemots showing Sucia sedimentary rock.

The following photos show some of the rock formations as well as botanist at work and play. And note the rock that looks like a sea lion.  (Some photos were taken by the botanists.)

matia matia-2 suciagroup-4 suciagroup

And finally for those that need a sea creature, I just sent this photo to Claudia Mills in hopes that she could identify it for me.  It was taken leaning over the side of the boat in the Sucia group.


Pray for weather like we had last week and spring!

– Philip



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