02 February, 2011

Oregon Geology Parte the Sixth: Three Capes

In less than twenty-four hours, we'd managed to pack in a lot of geologic yumminess.  We'd seen the mouth of the Columbia River, seen the Columbia River Basalts plunge into the ocean at Ecola State Park, hugged our geology at the north and south bits of Hug Point, and I'd just spent the early morning playing at the shortest river in the world.  Now, intrepid companion in tow, we headed back up the coast to meet Suzanne for the first time and walk into a lighthouse.

Of course we went the scenic route.  The Three Capes Scenic Loop, to be exact.

You can see an astonishing variety of geology in a very short amount of time along this loop, including one of the rarest of sights on the Oregon coast: a sandstone cape.  But if you're driving north up the loop, the first thing you'll notice upon reaching Cape Kiwanda State Park is sand.  Lots and lots of sand.

Dunes at Cape Kiwanda
After a day of seeing nothing much but basalt alternating with flat sandy beaches, it was rather a shock to see so much sand.  You don't get many sand dunes like this along the northern Oregon coast.  But sand working its way down from Sand Lake to the north piles up here to spectacular heights.  And depths.  This is one of the deepest sandy beaches I've ever walked across.

Here, you're catching a glimpse of what the beaches were like fifteen million years ago, before the basalt came.  And yet, basalt is the reason it's still here.

Haystack Rock (not to be confused with the other Haystack Rock)
This monolith, at over 300 feet tall one of the tallest stacks in the world, is a remnant of our old friend the Grande Ronde Basalt.  It used to be firmly attached to dry land, but not firmly enough.  It's connections eroded away, and what we're left with is this sentinel, which takes the brunt of the sea and prevents the softer sandstones behind it from eroding away.  So let's spend a moment paying our respects before moving on.  Besides, it's just mind-boggling to stare at.  It looms over the sandy beach and dunes like a hulking great chunk of basalt set down from nowhere.  Of course, you and I know it came from about four hundred miles away, and was awfully warm when it got here.

Right.  Let's see what it's protecting.

Cape Kiwanda
I have to tell you, I wasn't expecting this, and I was rather shocked when I saw it.  Hug Point was one thing - the sandstones there were so threaded through and buttressed by basalt that you weren't surprised to see them.  But this huge finger of nothing but lithified sand, along with the remains of some hapless clams and marine snails, jutting out into the ocean like that...  It's nothing short of astounding.

Until now, all we've caught are glimmers and glimpses of the Astoria Formation.  Here, it's bold and beautiful, standing naked and proud without so much as a stitch of basalt on.  And with that jaunty cap of vegetation, it looks positively saucy.  It seems to know it's special.

We didn't have time to trudge through the sand to get to it, but even from a distance, through a misty morning, the butter yellows and russet and umber colors stood out. 

Cave and Color
Hard to believe all those rich hues are the result of weathering.  The Astoria Formation, in all its micaceous sandstone and tuffaceous, sandy-shale goodness, is actually gray on fresh surfaces.

Oh, how I wanted to go play in that cave!  Run my hands over the sands, trace its history, drink it all in.  It's got stories to tell of a time when the Oregon shore had finally made it almost all the way west.  In the Miocene, sand piled up offshore in bays, submarine fans spread out from the young coast, and sea life lived it up for a while.  Then came the Columbia River Basalts, which proceeded to throw a clam bake on a scale never before seen in these parts.  Happily for the sea critters, the basalt stopped coming for about ten million years.  Unhappily for it, sea levels dropped in the late Pliocene, and spent the Pleistocene bouncing up and down like restless kids on a trampoline while glaciers advanced and retreated.

This part of the coast has been rising since the Miocene, and now bits of the Astoria Formation stand out above the waves.  Most of the nekkid bits of it got eroded away for their troubles, but thanks to the Grande Ronde, this bit of it can stand up to the waves and laugh.  Not that waves don't still attack it.  You can stand on the beach and watch wave after wave hit, gradually sculpting the cape into fantastic shapes.

Waves Hit the Cape
Waves here are tall enough for surfers to take advantage of.  The shore is gentle enough for dories to launch right from it.  And all the time, the dark bulk of Haystack Rock bears the brunt of the abuse so the rest of this coast doesn't have to.  It's a remarkable little spot.

On your way out, don't forget to stop by and pat the massive sandstone wall.

Sandstone Wall Goodness
I like that wall a lot.

Back to the Three Capes Scenic Loop we went, and swooped inland a bit, then climbed and climbed and came through a haunting little forest that gave out on one of those views that make you look wildly for a pullout.  And as we stepped from the car, we saw a plaque.

Gammon Launch
Here at Anderson Viewpoint, you can see where hang gliders hurl themselves over precipitous cliffs.  They can thank the Columbia River Basalts for giving them such a lovely launch.

Oh, yes, we're back to basalt.  But what makes Cape Lookout special is its shape, and what that shape tells us about it.  If you look at a map of the coast, you'll notice most of those massive basalt headlands are blunt and round.  This one sticks out like the paw of a very eager pointer.

It juts two miles into the sea, with cliffs up to eight hundred feet high.  Alas, we didn't get a good view of it, but a hell of a view from it.

From Anderson Viewpoint
Okay, so maybe it would've been a better view on a clear day, but still, pretty spectacular.  And what's even more spectacular is what we're standing on: hundreds and hundreds of feet of Grande Ronde Basalt that hurtled down an ancient canyon or valley and plunged into the sea.  Now, that low bit has become the high, all because it got filled up with lava.  Nice example of inverted topography, that!  If you're so fortunate as to be able to walk down it, you'll see nice basalt columns, and also pillows interbedded with sand and mud where the lava plunged into the ocean.

Even on a misty day, even just on a ten-minute stopover, you can see an amazing amount of geology.  So let's feast our eyes, then, shall we?  We'll begin with a nibble at a wave-cut bench:

Wave-cut Bench
The sea, you see, likes to chomp away at those tasty basalt headlands.  It masticates with waves, pounding air, sand and stones, and when it's chewed bits down to a nub, you're left with a wave-cut bench such as the above classic example.  That's the remnant of what must have once been a considerable hunk of Grande Ronde Basalt.  And it's the fate of all headlands along this coast, eventually.  Think of that when building a house along the coastline.

Now, let's take a broader view.

Netarts Spit
That narrow, hummocky bit of land there is Netarts Spit.  It's a sand spit that stretches six miles up the coast and protects Netarts Bay from the open ocean.  You can see the dunes covering the ridge, and you can see the chunks the ocean's taken out of them.  Spits form from waves hustling sand along the coast.  It's all in the angle.  One bit is connected to the mainland, in this case the south bit, close to where we're standing.

Now, the really neat thing about Netarts Spit is that it's merely an erosional remnant of a maclargehuge elongate dune that marched northeast.  It used to be connected to the mainland at its north end.  Then the seas rose at the end of the Pleistocene Ice Age, and the dune, stabilized by vegetation, found itself getting sliced open by the newly vigorous sea.

Those risen seas were also responsible for what you see looming out of the mists in the distance.

Three Arches
When sea level rose, it got to work carving out arches and stacks and wave-cut benches and all that lot.  Keep in mind that all those independent bits of rock jutting out of the ocean used to be headland, just like the bulky Maxwell Point to the right.  That's the power of water, my darlings.  It can take something massive and reduce it to ragged bits, and on a geologic timescale, it takes no time at all.

Speaking of no time, we had none.  Time to meet up with Suzanne in Oceanside.  You'll think it's a new day, but this is how rapidly the weather changes in Oregon.  It took us just half an hour to drive up by Netarts, collect Suzanne, and enthrone ourselves in a very nice coffee shop with a view of the ocean.  By then, the sunshine shone and the whole world sparkled.  And Maxwell Point basked.

Maxwell Point and Three Arches Rocks
Remarkable, right?  But not half so remarkable as that headland.  Have a closer look.  A fault runs through it.

I couldn't find much on that fault, alas, but one thing's for sure: when the ocean gets done carving away the basalt buttress, the rest of Maxwell Point's not going to be long for this world.  Looks distinctly sedimentary, that stuff on the right.  One day, I'll get back there and have a good long look at it, and scare up some geologic info.  There's supposed to be a tunnel through it, even.

For now, let us turn our attention to the Three Arches.

Three Arches

Granted, from this angle, they don't look much like arches.  In fact, you won't see how archy they are until we make it up to Cape Meares State Park.  But they have got arches, which likely began their lives as little sea caves or tunnels, back when this was all part of the headland.  Time and tide have dissected them neatly, and now they're a refuge for all sorts of local wild life: sea lions and murres, mostly. 

This is a good place to stand and watch the waves work.

Working Waves
The waves still whittle, and you can watch them worry at the base of the rocks, exploring crevices, driving holes through, and continuing the long job of planing off the knobbly bits.  Nature may abhor a vacuum, but oceans seem offended at the idea of knobbly bits standing up in them.

You can see the sea nibbling at Maxwell Point's toes, where they've got a good start on a wave-cut bench.

Wave-cut bench at Maxwell Point

And yes, all of that nice thick basalt you see is our old friend the Grande Ronde.  It's what you might call ubiquitous around here.  In fact, we're about to see great gobs of it.  On the other side of Maxwell Point lies Cape Meares State Park, where we shall look a lighthouse in the eye and see an upside-down waterfall.

Ye olde indispensable volumes of reference as the author was trying to make sense of it all:

Fires, Faults and Floods - one of the best roadside guides to the Columbia River Basin evah.

In Search of Ancient Oregon - simply the most beautiful book written about Oregon's natural history.
Hiking Oregon's Geology - chock full o' adventurous goodness sure to help you get your rocks on.

Northwest Exposures - tying the whole shebang together in one easy-to-follow narrative.

Cataclysms on the Columbia - the book that truly helped me comprehend the incomprehensible.

The Restless Northwest - short, sweet, and yet comprehensive guide to Northwest geological shenanigans.

Roadside Geology of Oregon and Roadside Geology of Washington - indispensable references and inspirations.

Glacial Lake Missoula and its Humongous Floods - not only an informative guide to the discovery and history of the Floods, but an apt title, too! 
And guest starring the following links:


Suzanne said...

yay -- netarts! lard love a duck, i've been to oceanside a buncha times and never noticed that fault.

Lyle said...

Now that you have seen the downstream ends (that are exposed) of the Grande Ronde basalt, you need to get to central and eastern Or, to see the sources of the basalt. Indications of fissures 5 to 10 m wide that erupted the basalt, give a hint of how much lava was flowing. Anyway in that part of Oregon there is a lot less vegetation to hide the rocks.
In one sense it would have been interesting to see the flows in action, but in another it might have been a good way to get cooked as well.

Dan McShane said...

Misty or not this leg of the trip looks like great fun. It' been far too long since I ran in the sand dunes.