Every Place Has a Story: Prichard, Oregon's Smallest State Park

I've been visiting Florence, Oregon for a number of years, and it is a beautiful place. The Siuslaw River reaches the sea near the town and at the northern edge of the Oregon Dunes National Recreation Area. Sea Lion Caves lie hidden in the coastal cliffs just north of town. But Florence holds one other distinction: it has Oregon's smallest state park. It's called Prichard State Wayside, and it totals an entire 0.5 acres. To be sure, Prichard is not the smallest park in Oregon. That distinction belongs to a city park in Portland called Mills End Park. It's located at in intersection in the city, and has a total area of 452 square inches.

A visit to Prichard State Park is not exactly a life-changing event. The half acre includes a grassy swale, a couple of trees, a small parking area, and no facilities at all. There's a single sign identifying the site. There's no interpretive signage, and little information on the internet about the history or genesis of the park. I'm guessing it was some land that was donated to the state, and the officials that be couldn't really decide what to do with it.

Looking at the park, I was reminded of something that I tell my students on the opening day of every class: geology is where you find it, and every place you find has a geological story. At first glance I was hard put to imagine an interesting geological story for this place. But a moment's reflection proved the opposite.

Let's take a look at the setting of the park. It is a grassy slope that is situated along the Siuslaw River, which from this angle looks like a huge body of water. But it isn't technically a river. It's a tidal estuary, and the wide body of water flows either downstream towards the sea or upstream in response to the daily tides. In a few hours the entire mudflat in these pictures will be covered with water. The area of tidal influence extends 26 miles inland, which is nearly 20% of the entire length of the river. Upstream of the tidal influence, the river is modest, with an average flow of about 2,000 cubic feet per second. That's less than a third of the more familiar Rogue River.

The story of any part of the Earth starts with the rocks that underlie the site. A quick look at the geological map of the park region shows that the "bedrock" is composed of "Qal", translated as 'Quaternary alluvium". Alluvium is our term for any of the loose sediment that covers the more solid rock underneath. "Quaternary" is the last little gasp of geologic time, encompassing the last 2 million years. The unit might include the mud of the estuary, river and or gravel, or dune sand. The Qal at Prichard is most likely slightly consolidated dune sands, which is a material that underlies most of the coastal areas in the vicinity of Florence. Sand carried along the coast by wave transport is blown inland by persistent onshore winds, forming the dunes for which Oregon Dunes National Recreation Area is justly famous.

The picture above shows the coastline just north of Florence. The region has undergone a significant change in the last hundred years or so. Migrating dunes can certainly be a problem in developed areas, so a European species of beach grass was introduced in the 1920s in an effort to stabilize the dunes. The grass worked too well, and sand has been trapped in the area adjacent to the shoreline, building into an ever higher ridge of grass-covered sand. The area inland has been starved of sand, so it has blown farther inland, leaving a low area called the deflation plain, a region now covered by small ponds and scrubby forests.

Sand is a famously unstable foundation for buildings (it's even in the Bible), but dunes that have been stable for centuries or millennia will sometimes be consolidated by calcium carbonate or other minerals in the groundwater. That is a much firmer surface to work with, and thus the development of the Florence area has been possible.

Going back in geological time often leads to strange changes in the appearance of the landscape. For instance, during the ice ages of the last 2 million years this little park would have looked far, far different than it does today. It's not because there was any ice; the glaciers that were present in Oregon were many miles away up in the Cascades. The big different was sea level. With so much ice locked up in the vast continental glaciers that covered almost all of Canada and northern Europe, sea level dropped to around 300-400 feet lower than today. Prichard State Park a few tens of thousands of years ago would have been perched on a terrace above a Siuslaw River ensconced in a deep river gorge hundreds of feet below. The outlet of the river would have been miles to the west of where it is today. 

One last aspect of the geology of any region is how it affects those who live there. Hazards present at Prichard would clearly include flooding and fires (especially in a time of global climate change). As noted earlier, the average flow of the Siuslaw River is about 2,000 cubic feet per second. The record flood on the river was around 45,000 cfs, and in that circumstance, the water would rise to inundate the little park.

The other very serious threat is that of tsunamis. These destructive surges of water could be developed by a massive earthquake on the Cascadia Subduction Zone that runs parallel to the coast. A quake has now been documented as having reached magnitude 9 in 1700. Such an earthquake is thirty times more powerful than the magnitude 8 quake that devastated San Francisco in 1906, and around a thousand times more powerful than the 1988 Loma Prieta earthquake (just short of magnitude 7). Tsunamis can also be generated thousands of miles away in places like Japan or Alaska. Whether local or distant, Prichard State Park would be a dangerous spot if a tsunami ever hit. There would be no "breaking wave" as is shown in many photoshopped images. The water instead arrives as a surge moving rapidly upstream at high speed. In moments, the park would be inundated to a depth of several tens of feet. The water would eventually recede, but then a second, third, and maybe fourth wave will follow.

Geology is everywhere, and everywhere has a geologic story, even Oregon's smallest state park. Check it out, if you can find it!

The Flip Side of Dune Stabilization: Dunes Unleashed in Central Oregon

In our last post, we had a look at the "carpeted" dunes of Florence, the ridges of wind-blown sand along the coast that have been "stabilized" by invasive European Beach Grass. The grass was planted in the 1920s and has spread from California to British Columbia. It's a real problem, and huge changes have taken place in the geography of the dune environments along the west coast, especially  at Oregon Dunes National Recreation Area.

The beach grass has displaced native plants and animals, and caused massive foredunes to rise above the beaches. The inland areas behind the foredunes became starved of sand, forming deflation basins where pools and lakes formed and forests thrived. These are all problems for the original ecosystem of the dunes, but there is the flip side: the stabilization of the dunes was done for a reason.

Not all of the dunes in the Florence region are covered by dune grasses. Sand that blew away from the deflation basin formed dunes on the eastern edge of the dune field and many of those dunes have not been covered by beach grasses. The dunes are still active, migrating eastward with the prevailing wind. And that's a problem, at least in some areas.

I was at a shopping center in town on a recent trip, and I wasn't having much fun (it was Christmas shopping or some such thing), but I had noticed the dune sands behind the complex and headed out to have a look. The sand ridge was huge and so steep I had to really search to find a spot to climb to the crest. I huffed and puffed my way up and was presented with the awesome view of clean dunes and a distant lake in the deflation basin (the picture at the top of the post).

But the crux of the sand problem was the steepness of the dune behind the store complex. It was  steeper than the angle of repose (the natural angle of the sand slope). It was immediately obvious that the huge pile of sand was encroaching onto the business complex, and there was a lot of sand. The dune tops were twice as high as the building. There is an ongoing battle to stop or slow the movement of the sand.

It looks like they've been bulldozing sand, undercutting and increasing the slope of the dune. It's no doubt an expensive fix, but falling back to the "solution" of the 1920s would be unthinkable today. The movement of sand is unrelenting, and there will always be problems at the back of this business complex.

Our sojourn in Florence was about to end. We didn't quite know what lay ahead, since we had only a single camp reservation for one night for the next four days. We were going vagabonding, a tradition (and sometimes a source of stress!). More to come...

The Carpeted Dunes of Oregon's Central Coast: The Principle of Unintended Consequences

So how about this plush carpeting on a sand dune? What? It doesn't look like a sand dune? Some people are such skeptics....let's find a trail...

There's the sand, with three or four feet of grassroots on either side.

We are at the north end of Oregon Dunes National Recreation Area near the estuary of the Siuslaw River in Florence. The grass growing on and covering these dunes is European Beachgrass (Ammophila arenaria), an invasive plant that was introduced in the 1920s. It was an excellent example of the principle of unintended consequences. The apparent solution of one problem resulted in a number of others.

There are some very specific problems associated with living along the Oregon coast between Florence and Coos Bay. The forty-mile stretch of sandy beaches and dunes ranges up to three miles inland and any roads or towns built there must contend with the instability of windblown sand and dune migration. The introduction of the European Beachgrass was seen as a way of stabilizing the dunes. In a sense, the grass did the job too well.

The grass has deep roots and spreads rapidly, overwhelming and replacing the native plant species. By anchoring the sand just above the shoreline, new sand blowing in from the beach is trapped in the grasses, causing the foredunes to grow higher and higher. Little of the new sand on the beach gets past the foredune system, and a form of stability is achieved.

Deflation basin in the south jetty area of the Siuslaw River

Without the infusion of new sand, the area inland of the foredune system becomes starved of sediment. The wind blows just as much and carries what sand there is farther inland, sometimes burying the forests growing there. What had been a dune complex with occasional islands of trees and vegetation becomes a deflation basin, a place where sand is removed to the local groundwater level. The wet ground and ponds found there become a stable surface where a thick forest can start growing. The dunes are stabilized to an extent, but much of the dune environment with all the native plants and animals is lost (see the comparison below).

Another problem with many invasive species is that they don't tend to stay where they are supposed to. The desired level of control was achieved in some places, but the grass continued to spread far beyond, invading areas like the Oregon Dunes where open dune environments were still desired. The beach grass is now found on coasts from Southern California to British Columbia. And it is extremely difficult to control or remove.

The grass can be pulled manually (by volunteers most of the time) but roots are always left deep in the sand and the grass soon sprouts again. The shoots have to be pulled seven or eight times before the grass is truly gone. It's hard work. Bulldozers and other mechanical means can be used, but the expenses are high. Some herbicides can be used as well, but the disruptions to the native species can be profound. All in all it is a sticky problem.

The coastal sand dune environment is a fascinating place to visit, and there are many recreational opportunities, but there are also opportunities to volunteer and help achieve a return to the natural conditions that existed before humans tried to mold the landscape to their liking. One place to start is the Oregon Dunes Restoration Collaborative which works to preserve and rehabilitate the dune system.

That's a Huge River! Well, Not Exactly...Sediments in the Siuslaw River Estuary

In the photo above we're on a hill overlooking the Siuslaw River near Florence, Oregon. From this point of view the river looks huge and indeed the channel is navigable and leads to a working marina a mile or two upstream. But looks can be deceiving, and a careful observer will note that the "river" spends half of the time flowing the wrong direction. Like two of the last posts here on Geotripper, the Moon is part of the story...this is a tidal estuary. The Moon has the greatest influence on the intensity of the tides.

There is a Siuslaw River, of course, but it is just not quite this big. It is 120 miles long, starting at an elevation of 636 feet in the Oregon Coast Ranges, draining an area of about 773 square miles. The discharge of the river varies greatly depending on the season. The long-term average is around 3,000 cubic feet per second, but last week when I was there it was a mere 145 cubic feet per second. During the worst of flooding the river can exceed 50,000 cfs. But it is the lower part of the river that is affected most by the tides. During extreme high tides, changes in river level can be noted 26 miles upstream.

An estuary is the portion of a river influenced by tides where there is a constant mixing of salt and fresh water. Estuaries are rich in nutrients and one of the richest biomass producers on the planet. The estuary of the Siuslaw River developed at the end of the last Ice Age. With so much water locked up in glacial ice, sea level was hundreds of feet lower than it is today, and the Siuslaw River occupied a deep channel that continued for miles west of the current coastline. As the ice melted, sea level rose and flooded the river valley, but the Siuslaw River carried vast amounts of sediment to fill the flooded channel, forming the flat level valley we can see today. Additional sediment is added by wind blowing sand from the coastal dunes that line the lower channel (the Siuslaw is at the northern end of Oregon Dunes National Recreational Area).

When I was there a week or two ago, we experienced an intense low tide that exposed some rarely seen sedimentary structures in the channel. When the tides rise, water rushes upstream, and when the tides fall, the water goes out to sea. Flowing over the loose silt and sand, the flow causes the development of gigantic ripples like those in the pictures above and below.

It didn't occur to me at the time, but this is not a natural channel. Because of the ship traffic, the channel is dredged to maintain sufficient depth for the boats to pass through. There are other changes in the last century. The drainage of the Siuslaw is one of the most heavily logged regions in Oregon, and the clearcutting of timber has changed the nature of slope failure and flooding on the river. Trees and logjams used to trap sediment upstream, providing a rich breeding ground for salmon. The logjams were removed and the river scoured the channel to bedrock in many places. One of the most destructive activities was the process of "splash-dam" logging. Temporary dams were built across the river and trees were cut and floated in the reservoir. The reservoir was then dynamited and the resulting flood carried the logs downstream to the mills. The practice, needless to say, was hugely destructive of the salmon fisheries. Over the years the salmon runs declined from hundreds of thousands of fish each year to mere thousands.

Some of the sources I checked pointed out that the Siuslaw once was the second richest salmon fishery in Oregon after the Columbia River. Efforts are being made to improve the environment to build the salmon runs. They'll never be what they were a century ago given the vast changes upstream, but there is a lot of potential for growth of fish populations. In the meantime, it is an interesting place to visit if you are ever lucky enough to find yourself on the central Oregon coast (especially during the present heat wave!).

Just a Beautiful Sunset, and Maybe a BIt of a Green Flash...

The gloom and the rain cleared out for our last night in Oregon, and we were treated to a gorgeous sunset. We had a clear horizon to the west, so as usual I tried to catch (maybe) a bit of the green flash.

The green flash is a somewhat rarely seen spectral phenomenon that occurs the moment the sun disappears below the horizon. Light from the sun is being refracted through the atmosphere, and at sunset the last of the spectral colors to appear is green (and sometimes blue). The effect only lasts for a second or two, so I'm never quite sure what I've seen. I just trust the camera to catch the effect, to varying success. 

My previous try was more convincing, but I see a bit of green in the picture below. You're welcome to tell me what you think!

Wandering Through a Sand Wilderness

To a child who was raised along the beaches of Southern California, the Oregon coast comes as quite a shock. Beaches to me were places like Huntington or Balboa, where wall-to-wall people struggled to claim a few precious square feet where they could lay out a towel, and get sunburnt from head to toe (yes, the cultural habits of the sixties were terrifying; I'm lucky to not have skin cancer yet). Nature involved gulls trying to steal one's food, and getting stung by the occasional jellyfish.

My perceptions of ocean coasts were changed somewhat when I moved to Central California. The beaches we explore these days, Big Sur and the Marin Headlands, are more cliffs than sand. They are beautiful beyond measure, but they are not like Oregon. Few places are like Oregon.

My explorations of the Oregon Coast these days are centered around Florence at the north end of Oregon Dunes National Recreational Area. It is a truly alien place to a Californian! The strangest part is the sand wilderness. For a fifty-five mile stretch of coast, the shoreline is dominated by sand beaches. Constant onshore winds have blown vast amounts of sand inland, in places as much as three miles. In some localities the dunes buried mature forests. In others, forests have grown over the dunes. With the plentiful rainfall, the groundwater table is high, so many of the low places between dunes are occupied by lakes, ponds, and swamps. A fair number of them are large enough for boating and water sports. Others are more appropriate for hiking, wildlife observation, and contemplation. Our brief visit on Black Friday included a look at small Dune Lake adjacent to the national forest campground at Alder Dune (above).

Our other exploration was the short boardwalk at Holman Vista. The handicapped accessible trail provides access to Sutton Creek where it flows through a network of dunes and swamps, with a view of the distant mountain slopes as well. The dunes adjacent to the beach are anchored in place by European Beachgrass to augment the stabilization of migrating dunes (the original plantings were in the early 1900s when people didn't worry too much about the possible adverse effects). The native grasses have been pushed aside as the European non-native grass takes over. Because of the spread of grasses, 80% of the dune sheet is covered by vegetation. In 1939 it was only 20% (US Forest Service data).

The nature trail also offered what it termed "a view of the beach". That was true in the sense that an apartment might have a beach view if one leans out the window and cranes one's neck to see a bit of water in the distance between other buildings. In the picture above, note the beach view, a bit of white left of center. Look below for the zoomed view. We were in the midst of a series of powerful storms, so the surf was pounding the coast.

As I've pointed out in previous posts, the sand has several origins. The quartz rich sands were eroded from distant sources in the Klamath Mountains and Idaho Batholith and carried to the shoreline environment by one of Oregon's many rivers. Other sand is locally derived, eroded directly from the sea cliffs, or carried onshore from offshore bars. Some of the sediment that may have originated during the ice ages when sea level was lower. Wave action produced the flat platforms on which the dunes accumulated. 

Although I call this a sand wilderness, it is not officially designated as one, but it is managed as a de facto wilderness. Vehicles are not allowed off the paved roads, so access is by trail only, or by beach walking. Access to parts of the beach is restricted during the spring because endangered Snowy Plovers nest in the area.

To this Californian, it is a true shock to look at an eight mile long stretch of beach and not see a single person. It was heavenly!

The End of Fifty Miles of Sand: The Oregon Dunes

Or maybe, more properly, the beginning of fifty miles of sand. It's generally moving south from this point. The west coast of North America is mostly mountainous, with dramatic cliffs sloping almost directly into the sea. Where the east and south coasts of the United States might have strands of sand that run for hundreds of miles, sand is rare enough in the west to be a curiosity. If fifty miles of sand is found in one place, it is extraordinary. That's where I spent my Thanksgiving, next to Oregon Dunes National Recreation Area.

I've always made a point of resisting the orders of our superiors to go out and buy things the day after Thanksgiving, being a firm supporter of the the idea to "leave no child (or anyone else) inside" as a form of personal education. We went exploring the coastal area around Florence this weekend.

As I've noted in previous blogs, the so-called Coos Bay dune sheet extends for 56 miles (90 kms) from Coos Bay to Florence, and it is a strange and bizarre landscape that contains 85% of Oregon's active dunes. It's mostly protected as Oregon Dunes National Recreational Area. It isn't that there is simply a long expanse of sandy beach; the sand has been blowing and migrating inland, in some places nearly 3 miles, covering forests in some cases, and in other situations, stabilizing and becoming forest. This odd environment makes for unique ecosystem and geological landscape, mixing ocean, swamps, rivers, forests, and lakes.

You can get a hint of the transition of dune to forest in the pictures here. I was quite literally standing above the very last dunes of the system, about eight miles north of Florence, where cliffs once again dominate the shoreline. The irregular hills are sand dunes that have been stabilized with European Beachgrass to augment the stabilization of migrating dunes. The native grasses have been pushed aside in many instances as the European non-native takes over. Because of the spread of grasses, 80 % of the dune sheet is covered by vegetation. In 1939 it was only 20% (US Forest Service data).

Only a few hundred yards inland, conifers have started to take root.  The rivers and streams that flow into the dune fields, along with a high groundwater table, have created a network of swamps, and more than two dozen ponds and lakes (before I began exploring this region I would have said that lakes form only from glaciers, sinkholes, landslides, or oxbows on floodplains; dune lakes were new to me). The complex provides a rich environment for wildlife.

The sand has several origins. The quartz rich sands have been eroded from distant sources in the Klamath Mountains and Idaho Batholith and carried to the shoreline environment by one of Oregon's many rivers. Other sand is locally derived, eroded directly from the sea cliffs, or carried onshore from offshore bars, sediment that may have originated during the ice ages when sea level was lower. Wave action produced the flat platforms on which the dunes accumulated.

It's a beautiful and dramatic landscape. If you ever get the chance...well, make the kind of choices that will get you chance to explore places like this!

Vagabonding on Dangerous Ground: Into the Land of Sand and Exploding Whales

The Cascadia Subduction Zone has raised mountains. The entire length of the convergent boundary, from California to British Columbia is marked by incredibly rugged cliffs and steep, forest-covered topography. There aren't a lot of sandy stretches of coast in southern Oregon, the kind that folks from Florida, south Texas, or the Atlantic seaboard would recognize. But in the central part of the state, there is one section of coast that is extraordinary.

The so-called Coos Bay dune sheet extends for 56 miles (90 kms) from Coos Bay to Florence, and it is a strange and bizarre landscape that contains 85% of Oregon's active dunes. It's mostly protected as Oregon Dunes National Recreational Area. It isn't that there is simply a long expanse of sandy beach; the sand has been blowing and migrating inland, in some places nearly 3 miles, covering forests in some cases, and in other situations, stabilizing and becoming forest. This odd environment makes for unique ecosystem and geological landscape, mixing ocean, swamps, rivers, forests, and lakes.

The sand has several origins. The quartz rich sands have been eroded from distant sources in the Klamath Mountains and Idaho Batholith and carried to the shoreline environment by one of Oregon's many rivers. Other sand is locally derived, eroded directly from the sea cliffs, or carried onshore from offshore bars, sediment that may have originated during the ice ages when sea level was lower. Wave action produced the flat platforms on which the dunes accumulated.

I've only just begun to explore this incredible landscape. I'm usually based out of Florence, so that's where these photos are coming from. Wave action is intense and unending. At times the waves are huge, and onshore winds can approach hurricane velocity. The first ridge of sand, the foredune, absorbs much of the impact of the wind and waves.

The dunes here have been altered extensively in the last century. Urbanization, where it's taken place has been secondary. The big changes resulted from the construction of jetties at the mouth of the Siuslaw and other rivers, which back up the sand along the coast as efficiently as a dam. The other has been the introduction of European beachgrass to augment the stabilization of migrating dunes. The native grasses have been pushed aside in many instances as the European non-native takes over. Because of the spread of grasses, 80 % of the dune sheet is covered by vegetation. In 1939 it was only 20% (US Forest Service data).

The rivers and streams that flow into the dune fields, along with a high groundwater table, have created a network of swamps, and more than two dozen ponds and lakes. Some of the larger lakes have been developed as recreational resorts.The complex provides a rich environment for wildlife, both local and migratory.

One very bizarre species in the area is the Darlingtonia californica, the carnivorous Pitcher Plant. I've written about the small park north of Florence previously. The plants can only grow in nitrogen poor environments like bogs or in serpentine soils. They get their nitrogen from the insects they consume.

One of the hazards of human colonization and development of the extensive dune field is the migration of the dunes over time, which could cover railroads and highways. That was one of the prime reason for efforts at dune stabilization in the early 1900s.

Another hazard, one not truly experienced in modern times, is the effect of large tsunamis in the event of a gigantic earthquake along the Cascadia Subduction Zone. Many of the lowland areas are expected to be inundated by tsunami surges that could reach depths of several tens of feet. Evacuation routes are prominently posted in developed areas.

There is one more hazard that Florence is rather famed for, although they probably wish it could be forgotten: exploding whales. If you haven't seen the video, you are in for a "treat". There is an extensive web presence if you want to learn more!