Monday, June 30, 2008
Bishops Beach lies north of Homer and is made up of sediment ultimately bound for the Spit. It is backed by high bluffs of Tertiary and Pleistocene sediments - typical of much of the Cook Inlet shoreline other than around the mouth of the Kenai River.
Bluff Point, where coal was once mined, lies north around the corner from the bluffs in these pictures, and is the site of a very large prehistoric landslide - the highway out of Homer skirts it's top edge.
At Bishop's I saw smaller landslides, along with some pretty foolish, or at least poorly regulated, bluff-top development. I suspect this is a shoreline we will all regret in 10-20 years - but will do nothing now to protect!
Yukon Island is across the bay from Homer. Most of it is rocky, but there are several pocket beaches and at the southeastern corner, a cuspate foreland (two spits or barriers converging to form a triangular shaped landform).
The geology (and terrain) divides dramatically from one side of Kachemak Bay to the other. Here it is a melange of older ocean floor and trench rocks, including these radialarian ribbon cherts from the mesozoic McHugh formation, formed from the exotic skeletons (they're cool - google images of radiolarians) of long-dead zooplankton settled out on the deep ocean floor and then thrust to the surface where geologic plates collided.
Sunday, June 29, 2008
One of the more intriguing things about Homer's beaches is the presence of coal. At one time, coal was mined along the high bluffs north of town - particularly near Bluff Point. Coal is light and must have different transport characteristics than other sediment, but it should come as no surprise that it gets carried by drift and spread out on beaches from Bishop's all the way to the tip of Homer Spit (also called Coal Point, because that's where it was once loaded on ships). It reminds me a bit of the chunks of peat on Whidbey Island's beaches, but the BTU content is probably far better. One guy on the web reports driving out to the beach and loading up his car with it -- saving him big bucks on winter fuel costs. I saw a man filling buckets in the back of his pickup with a shovel at Bishop's Beach one day - maybe it was the same guy?
Beluga Slough is a tidal marsh and lagoon on Homer's northern shoreline, between Bishop's Beach and Munson Point. It has formed in a long, low trough, the upper end of which has been dammed off by the road to create the lake the seaplanes land on. There's a nice view of the Slough from the Alaska Islands/Kachemak Bay Visitor Center and easy access from Bishop's Beach and the Two Sisters Bakery.
The slough is linked to the sea via a tidal inlet that gets pushed by longshore drift westward toward Munson Point. This poses a problem for the private property owners on that side, so apparently someone goes out and rearranges the channel now and then. It must be a challenge for naturalists working on the marsh when some eight-year old asks them why there is bulldozer in the slough or out on the beach.
I chose our lodgings in Homer before doing my pre-trip geology homework. It was only fitting, but highly ironic, that I found I had chosen the center of the local seawall controversy.
The wall is hideous, but as usual, the folks living above it don't have to look at it. And given Alaska's propensity to largesse, they may not have to pay for it either. A fairly small number of property owners get the views and the perception of being one with the environment, but the kharma is all wrong. There is nothing sustainable about this place. What is natural about this place is the eroding bluff, not the static view of the bay from the rampart of an engineered fortress.
The beach is eroding beneath the wall - the underlying till was exposed on the beach in front of the section of the wall that failed this past January. This wall will only get bigger. The wall encourages more investment in bluff top property, not less, so the likelihood of retreating becomes less. I'm all for property rights: the right to buy lemons and accept the consequences of investment choices. The issue of whether you can muck up a public resource or incur public expense to protect property value is not about property rights but something else.
In this case, I think the area of concern is sufficiently small that maybe the expedient solution may a government bailout -- not to build a bigger wall but to buy out the property owners and pull out the wall. Call it Munson Point Park. I can't believe doing this won't be cheaper (and better public policy) than even a decade or two of seawall maintenance and replacement.
There were some interesting twists. Each end of the wall is marked by barrier beaches - a small accretional feature at the updrift Munson Point end and the base of the much larger Homer spit at the downdrift end. The tide range is 20-30 feet, so there are wonderful sand and gravel bars and flats exposed at low tide, sprinkled with some big boulders. As we sometimes see on Puget Sound, high points on the gravel beach along the seawall correspond to the landward end of large tranverse sand bars that extend far offshore. And that may shift down shore fairly quickly - changing the locus of seawall damage from one year to the next.
Saturday, June 28, 2008
What an elegant concept - a long, sinuous spit extending out across Kachemak Bay towards the snow covered peaks of the Kenai Range. From the hills above town the concept holds up well. Down on the spit, the elegance of the concept is blurred a little bit by the frontier-style development.
The beaches consist of sand and gravel transported from bluffs along Cook Inlet northeast of town (Bishop's Beach), but the foundation of the spit may be a moraine left by a glacier that once reached this far down Kachemak Bay.
In the 1964 earthquake, the spit, along with most of the Kenai Peninsula, dropped several feet. This pretty much neutralized any dry land on the spit's backshore, so most of the dry ground found today is the consequence of an enormous amount of fill added on top since then.
The spit is a five-mile long riprapped causeway with acres of parking lots, souvenir shops, and fish packing operations, plus a large marina and numerous port facilities. Some of the tourist places and restaurants are on piles hanging over the beach, as are some brand new condos near the tip. There were folks camping all along the beach - one of several scenes that contributed my image of Alaska beaches as gravel backshores lined with RVs.
I'd love to know more about how the shoreline has responded in the 44 years since the earthquake. Subsidence reduced the size of the spit and in the absence of human intervention, would have resulted in the shoreline shifting tens or hundreds of feet landward, but at the same time, subsidence might also have led to dramatic increases in updrift bluff erosion and the potential for a big pulse of new sediment to move towards the spit. I wonder if the multiple gravel berms on the outer face of the spit can be attributed in part to decades of earthquake-induced sediment supply?
The spit was equipped with tsunami sirens, but I doubt most of the folks on the spit would know what to do if they went off. At 3PM on a summer afternoon, as the halibut boats pull in and the gift shops are full and the ferry is unloading, the evacuation might be tricky. By the time people got the awning rolled up and the satellite dish folded away, the RV would already be floating upside down in the marina.
I would have enjoyed more time to explore the beaches along Cook Inlet, but the timidity of our car, the patience of my family, and a need to move on to Homer kept us to a few quick stops. Ninilchik is a small town with a small Russian church perched on the hill and a fish and chips place built on piles over the beach. The wooden groins, wood revetment, and shingle beach reminded me of pictures of the British coast.
Thursday, June 26, 2008
I picked up a copy of John Muir's Travels in Alaska at the lodge and started reading his accounts of visiting Glacier Bay in the 1800s. Everything in these photos was still under thousands of feet of ice at that time. The glacier named after him is now hidden, having retreat far up it's valley (Muir Inlet), and our boat didn't pursue it.
Two glaciers still emerge from the Fairweather Ice Field into the head of Tarr Inlet - the Margerie and the Grand Pacific. The former is the classic calving glacier, a face of blue ice several hundred feet high with relatively little rocky debris except at its margins. The Grand Pacific, at least from this perspective, is an enormous load of dirt being carried to the sea by the ice. It also appears to have retreated far enough so that it is barely qualifies as a tidewater glacier.
As you head up Tarr Inlet, you are following the retreat of the ice. 20 miles from the glacier, the landscape is many decades old, the geology has begun to settle down and the forest has moved in. As you approach the glacial front, the landscape gets younger - alder thickets on highly unstable rocky slopes. And in front of the ice, the land is only freshly exposed and there is no obvious vegetation.
In the photo up the alluvial fan into the mountain valley, you can see sloping lines (they are subtle) in the trees to the right of the stream showing a series of terraces developed as the stream has rapidly cut down into the ravine. The photo of the kayaks on the beach contains an intriguing feature. The beach, although it is a very young feature, is a fairly ordinary gravel beach (as far as I can tell from the boat), but it is backed by a higher terrace - something I did not see widely exposed elsewhere on the inlet. I'm guessing this is a remnant of a backbeach formed many decades ago, after the glacier retreated past this point, but before significant rebound had occurred. It has now been lifted beyond the reach of the waves and tides. In most places, this feature would be eliminated by subsequent erosion, but here it has been preserved - at least for another decade or so until the beach erodes back across it.
Wednesday, June 25, 2008
Bartlett Cove is near Gustavus at the southern end of Glacier Bay and is about where Vancouver reported seeing the ice front when he passed in 1792. Today, you must head fifty miles or so up into Muir and Tarr Inlets to find glaciers that reach tidewater - an impressive retreat of the ice over a few hundred years. The advance of glaciers down Glacier Bay occurred during the so-called Little Ice Age of the middle part of the last millennium and this rapid melting began before industrial CO2 emissions began to rise. It is neither proof, nor disproof, of human caused climate changes - although both sides cynically use it to their advantage. It simply underscores the complexity of our climate system and the importance of recognizing long term variability in natural systems.
Large glaciers are heavy and press the earth's crust downward. When the ice melts, the crust rebounds, often quite quickly. This is a major influence on Glacier Bay's shoreline - Bartlett Cove may be shooting upward an inch or more a year (which translates to about 10 feet in the last century). This is hard to distinguish in an area subject to large tides and storms, but over time it lifts old shorelines and beaches out of the sea. In Bartlett Cove, the old shoreline marches up into the forest, or conversely, the forest appears to be marching out onto the shore. Grasses begin to occupy the areas removed from the influence of the highest tides and then eventually alder and then conifers appear.
In an era of concern about increasing sea level, it is ironic to be visiting shorelines that are rising faster than the ocean. These shorelines remind me of those I saw on Lake Huron in May, where water levels have also been falling. I'll have to wait until the Kenai Peninsula to look at shorelines where sea level has actually risen.
Tuesday, June 24, 2008
Juneau has several claims to uniqueness among state capitals - northness, no road connection to the rest of the world, a power supply that can be brought to its knees by avalanches, and it's very own glacier.
The Mendenhall Glacier has retreated across this landscape in the last few decades, exposing gravel to wave action in the lake, generated by winds blowing down the glacier. The result is this nice little recurved spit right in front of the viewpoint.
Sunday, June 22, 2008
Ketchikan’s tide range must be12-15 feet, at least. A waterfall marks the head of tide on this small stream mouth estuary. The stream gradient is steep, so when the tide is low it’s a fast flowing stream with muddy sides.
In southern Puget Sound, drowned stream mouth estuaries result from rising sea level flooding valleys carved thousands of years ago when sea level was lower. Here, where I suspect the coastline is rising out of the sea, the estuary is probably formed by a steep stream cutting a ravine into the uplifted shoreline as it tries to reach low tide.
Creek Street was brothels and bars 100 years ago when the prospectors sailed north to find gold. Now it’s souvenirs, native crafts, and t-shirts with cutesy slogans about fishing towns, tourists, and historic professions.
Monday, June 16, 2008
This sandy beach is located where the beach rejoins the island after its brief seaward excursion out and around Flat Point, a small cuspate foreland (or a recurved spit) on the northwest shore of Lopez Island.
It's sandy, I suppose, because there isn’t sufficient energy to move gravel from the west side of the island around the corner to this more protected resting spot and also because their is simply lots of sand accumulating in this spot. Odlin Park, another north-facing pocket beach a little farther east is also sandy.
This is Upright Channel State Park, though as I recall, it may also go by another name. The beach in this largely undeveloped park is a 10 minute walk from the parking lot.
Sunday, June 15, 2008
Sunday morning brunch and a short walk on the beach. It was a beautiful day with scuba divers, beach walkers, boat launchers, and folks scrambling to get the new marine center ready for its grand opening tomorrow (Highline MAST)
Previous Post: Redondo (February 2006)
Saturday, June 14, 2008
Another site that I revisit frequently. The spit has continued to consolidate - the earlier second channel across the berm has vanished and the outlet is now clearly established at the northern end of the nascent lagoon. The berm/spit has widened with the accretion of a new berm seaward of the original berm crest. I don't see much evidence the that the berm has increased in height - maybe we need more gravel and a big storm to do that. Tidal currents have transported sand into the mouth of the lagoon, forming a small flood-tide delta. Organic material is continuing to accumulate in the lagoon and high marsh? vegetation is beginning to establish on the higher margins of the lagoon.
Schedule and lack of foresight are poor excuses, but I really should have worked harder to encourage some rigorous monitoring and surveying of this site. I suspect there are some valuable lessons about beach development, barrier lagoon dynamics, and salt marsh restoration in the evolution of this site. I know some folks are monitoring some elements of this - but they are probably focused more on fish use and coarse-scale landform change - not the details of morphology or of habitat formation.
This isn't the first post about Point Wilson, nor will it be the last. It's just a nice case study in the conflict between a static human (albeit a rich cultural one) landscape and a moving shoreline - and one I have the opportunity to revisit fairly frequently. The north shore is moving south. The riprap and the lighthouse and the parking lot are not. Pretty simple problem; not so simple a solution.
Previous Posts: February 2008, June 2007, November 2006
(or go to the map to locate posts from nearby sites)
Regular readers (that's an interesting assumption, isn't it) will note a shift in my approach to geo-locating posts. Previously, the titles of the posts from the Puget Sound region linked to a series of Ecology air photos. From here on I will be linking to Google Maps, since it provides better interactivity with other posts and photos. I may gradually go back and update links in previous posts. I may retain linkage to the Ecology air photos, but I'll do it in a different way (e.g. Point Wilson). I wish I could link to our more recent oblique photos - but currently the agency's map server doesn't allow this.
The bluff rising above the beach has been eroding for thousands of years and the beach has been moving back with it. The erosion has been gradual, persistent, inevitable. Every few years chunks of the bluff collapse on the beach, forming piles of talus to be gradually removed by the waves. In another 100 years, the bluff will look much the same, but it will be located a few tens of feet farther inland.
Beaches and bluffs retreat as a system. Efforts to protect the toe of the bluff from further erosion fundamentally disrupt this system. They decouple the beach from the bluff: one stops, the other keeps moving. We tend to focus on specific effects of armoring - loss of sediment supply, changes to riparian vegetation patterns, modification of beach substrate that could impact forage fish spawning or infauna abundance. Some of these may be minimized or mitigated with creative design, but I think the real problem is this systems problem. The system has to move to stay the same. For our grandchildren to see the beach as we see it today, it must be allowed to erode.
The views are spectacular from this beach - to the south (at least on a clear day) Mount Rainier looms above the distant Seattle skyline and to the west the Olympics are seen over Foulweather Bluff.
Double Bluff has two parts (hence its name, I suppose). This is the northwestern portion - at the southern end of Mutiny Bay. The layers exposed in this bluff record a complicated history of glaciations. This is the type section of the Double Bluff Drift - the spoils of an ice age that occurred 100,000 years before the most recent one. 1-2 miles to the east lie the high sandy bluffs that mark the eastern portion of Double Bluff (April 2006).