Life on the Outer Coast

This evening went to a talk given by Jim Baichtal on the changing shorelines of southeastern Alaska. He is an engaging speaker and did a nice job of pulling most of the pieces of the story together. Alot of the ideas he presented I had heard piecemeal previously, it was very good to hear them knitted together.
I'll see if I can summarize the broader picture of the late glacial history of southeast and his talk. The two peaks of major glacial event of the Wisconsin were around 72,00 and 20,000 years before present. The maps on Tim Heaton's website http://www.usd.edu/esci/alaska/ show the furtherest extent of the ice from the previous ice age (135,000 years before present) covering most of southeast. The maximum extent of glaciers during the Wisconsin glaciation was a bit less and there were significant areas on the outer coast that werent' glaciated. What was interesting about tonight's presentation was how the fore bulge in the earth's crust was used as an explanation for the extent of the refugia. The idea of the fore bulge is that the crust is displaced by the weight of the ice and pushed outward in areas that weren't carrying an ice load. So not just that the ocean depth was shallower because of water being held as ice, but displacement of the crust raising the land. (I really liked his waterbed analogy). One question I'll have to ask him or someone is about the crust, itself, is it the continental crust (thicker but less dense) or the oceanic crust (denser, but thinner) that is being displaced. I'm assuming that it is the lower less solid crust that is actually being displaced and pushing up the upper layers, but I could be wrong and the surface crust is what is being moved sideways and up.
The extent of the bulge would have been quite local, It sounded like it was dependent on the load of nearby ice and perhaps on the thickness of the crust at a given spot. The bulge was much smaller off southern southeast. He had pretty interesting maps of the outer coast of southeast which had the presumed refugia or ice free land. The inside channels were a bit muddier for me. If I'm remembering correctly that shoreline must have been higher than currently. The On Your Knees cave is currently at 490 ft above sea level and ca .6 miles from the shore and has ring seals, arctic fox fossils . I guess that fox could have carried their food up the hill, but it seems likely that the cave was significantly closer to the sea.
He seemed very certain that the bulge around Sitka was huge compared to the bulge on the outside of Prince of Wales island. If I remember right, most of the evidence for the extent of the bulge is the freshwater lake diatoms and pollen that were found in cores taken in Sitka Sound. If the sea level was about 70 fathoms lower and adding in the possible effect from the bulge, the 100 fathom curve might be a good approximation of where the shoreline was. The 100 fathom curve is between 10 and 15 miles off shore. Added to this freshwater evidence and ocean depths, is that the local contractors haven't encountered any marine clays/shells when excavating. Makes alot of sense if the shoreline was way off shore. The marine clays are quite distinct colorwise, even if there weren't clams, the material would be recognizable.
What wasn't clear was if the Queen Charlotte fault was a cliff? Would the bulge affect the crust on the other side of the fault the same way as on the landward side?
Tom Ager had told me about the freshwate diatoms and pollen from Sitka Sound on his visit this summer, so it wasn't a new idea, but seeing the map made it a bit more tangible. We were talking about this last summer while looking our across Sitka sound and I was envisoning walking from Mary's on Harris island to my house on Galankin. I like the image of walking through open Pine and fern forests to town. I'm hoping that Tom comes in April to tell us about the glacial history of Sitka sound. It is sounding more probable.

One thing that was especially intriguing was the carbon layer that Baichtal talked about finding in the 9,000 years present layers. I wasn't sure if that was something that he had only found on the southern islands or if it is more extensive. He was suggesting that the source of the carbon could have been forest fires. That was a new idea for me. Admittedly it isn't a hard leap to make with a pine forest and a carbon layer. I'll have to talk to Tom about it.

Seem to have gotten sidetracked on my glacial history. As the glaciers receeded the weight was lifted, the sea level rose and the fore bulge disappeared. One of the ideas he presented was that the movement of the crust was involved in the volcanic activity that occured near the time period (11,000 years before present for Mt. Edgecumbe), something near Ketchikan (?) and Addington near Noyes Island.
By 8,500 years before present the shoreline seems to be very similar to what it is currently allowing for uplift. He started his talk with a discussion of ancient marine clays and clam shells that he had been finding in various elevations and distances from the ocean in southeast.
The biota of glacial age is pretty intriguing as well. He started his talk with a discussion of ancient marine clays and clam shells that he had been finding in various elevations and distances from the ocean in southeast. It was a good way to introduce how the areas in southeast varied in affects of rebound and forebulge influence. I'm inspired to look for creek clams on my trips out of Sitka sound. I'm also inspired to look for odd plants down in Sandy and Whale Bays. There really isn't enough botany in the stories at this point in time.
The pieces of the corroborating evidence that story that are interesting are the subspecies of small mammals including Flying Squirrels that occur on Prince of Wales and the mice on Coronation. Again it would be interesting to find the plant stories that could support the story as well. What I have heard so far about the vegetation (in a general way) is that the pine forests were most abundant around 12,000 years ago, then displaced by spruce (10,000 years ago) and eventually western hemlock.
Had breakfast with Jim, Scott and Natalie in the morning, but mostly talked about elk. Heard some horror stories about how the elk are destroying the alpine on Etolin. Not sure why the hunt isn't more extensive nor why it isn't legal to hunt elk any time of the year if they aren't on Etolin or Zarembo islands. I think he avoided tonight's topic because he wanted to make sure that we all attended the talk. He did say that he planned on speaking at the Paths across the Pacific conference this summer. Tom Ager is as well, so it should be a good one.
The rest of the week: walked around the lake Sunday afternoon. The sun had come out and I had graded papers for about as long as I could stand.
Not alot of variety of birds, but it was nice to go outside. Found 29 Barrow's goldeneyes, 12 Common mergansers, 2 Harlequin, 1 Glaucous-winged gull, and 4 Buffleheads by dock.
In the alders around the lake and in the garden several Golden crowned kinglets, 3 Winter wrens, 3 Song sparrows, 5 Juncos, 8 Cchickadees, about 37 crows. The crows were raiding the feeder or at least trying to. They have a hard time with the hanging feeder, but they are tenacious.

Found another downed tree by the cabin. I'm fairly certain that it went down last week. I hope that I can find a few more upturned stumps to document this year.

Monday found it necessary to wear my headlamp this morning on my way to town. Too dark for a morning commute bird count.Tuesday faired better without a headlamp, but went in a bit later. 3 buffleheads by the dock, 4 pelagic cormorants on the commute.
Very whippy ride home Tuesday night. Strong westerly chop in the squalls.