A Landing a Day

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Mount Shasta, California

Posted by graywacke on September 15, 2013

First timer?  In this formerly once-a-day blog (and now more-or-less a twice a week blog), I have my computer select a random latitude and longitude that puts me somewhere in the continental United States (the lower 48).  I call this “landing.”  I keep track of the watersheds I land in, as well as the town I land near.  I do some internet research to hopefully find something of interest about my landing location.  To find out more about A Landing A Day (like who “Dan” is and what the various numbers and abbreviations mean in the first paragraph), please see “About Landing,” (and “Abbreviations” and “Cryptic Numbers”) above.

 Landing number 2052; A Landing A Day blog post number 470.

Dan –  After a one-for-nine, I’ll take this USer landing in . . . CA; 95/110; 2/10; 9; 152.2.  Here’s my regional landing map:

 shasta landing 1

My closer-in map shows my proximity to (what else?) Mount Shasta.  OK, so the town of McCloud’s not far, but the big mountain has my heart (and this post):

 shasta landing 2

I landed in the watershed of the McCloud River (2nd hit; more about the McCloud later); on to the Pit River (also 2nd hit); on to the Sacramento River (26th hit), on to the San Francisco Bay, under the Golden Gate Bridge, and out to the Pacific Ocean.

 My Google Earth (GE) shot shows that I landed in the woods (in a surprisingly non-mountainous area):

shasta GE 1 

Zooming out some, I see a peculiar irregular patchwork east of my landing:

 shasta GE 3

Taking a closer look, I’m mystified.  Maybe clear-cutting of patches of forest (for timber), but new growth has either not been planted or just been planted?  

 shasta GE 4

Enough about the patchwork vegetation.  How about Mount Shasta?  Well, here ‘tis:

 shasta GE 5

Of course, I had to tilt my perspective, and see the big mountain looming behind my landing:

 shasta GE 6

Just so you know, I have GE set with no vertical exaggeration. 

 So, what to say about Mount Shasta?  Obviously, there’s a whole lot of geology going on.  But you know, back on July 31, 2011, I landed near Mt. Rainier, and I discussed the volcanic geology at some length.  Generally, it all applies as well to Mt. Shasta.  In my Rainier post, I also talked about lahars (volcanic mudflows), and the potential for catastrophe in the event of an eruption.  Once again, it applies to Shasta.  Click HERE to check out my Mt. Rainier post.

 So, as I was pondering the geologic angle for this post, I decided to go big picture.  Why are Mt. Shasta and Mt. Rainier (not to mention Mounts Hood, Lassen, Adams, Jefferson, St. Helens and Baker, as well as Crater Lake), here at all?  What’s going on?

 We all know about spreading centers (like the Mid-Atlantic Ridge), where semi-molten magma rock wells up and forms new crust that spreads out away from the ridge.  Well, there are several of those in the Pacific Ocean.  They go from Northern California on up into British Columbia.  Here’s a map (Wiki):

shasta geology wiki

The spreading centers are three ridges labeled Explorer Ridge, Juan De Fuca Ridge and Gorda Ridge.  See the arrows?  They indicate the new crust being formed and spreading out away from the ridge.  Of course, you can also see all of the volcanoes.

 Realize that not only is the newly formed crust headed east, but the North American plate is headed west (pushed by the Atlantic Ridge spreading center).  Hmmmm.  Something has to give.

 Look back at the picture.  See the dark line in the ocean not far from the coast?  That’s the subduction zone, where the newly-formed oceanic crust plunges under the advancing North American Plate. 

 OK, we need another picture, this one a cross-section.  Wiki let me down a little.  No cross-section!  But I found one at volcanic legacy dot net:

 shasta volcanic legacy.net  cross section

Now you can see what happens.  The oceanic crust grinds its way under the North American crust.  Guess what happens as this immense rock mass bullies its way under North America?  It heats up.  It heats up big time, such that at the plate boundaries, the rock becomes liquid lava. 

 Heat rises, as does the molten, liquid rock.  A crack here, a slightly weaker zone of rock there, and up it goes until it breaks out at the surface.  Voila!  A volcano.

 Back to Wiki, here’s a graphic that shows the frequency of eruptions of the various volcanoes.  Think there might be a bang or two in the not-too-distant future?

 shasta geology 2 wiki

My more astute readers may have wondered how it is that the entire North American continent is being pushed by the spreading center that is way the heck out in the middle of the Atlantic Ocean.  Excellent wondering.  It turns out that the Atlantic oceanic crust and the North American continental crust are locked and are behaving as one.  The result is a stable east coast in the United States.

 Let’s imagine for a second if the Atlantic crust began plunging under the North American crust along the east coast.  Oh, it would take a few million years, but look out for the massive earthquakes!  Volcanoes popping up all over the place!  Bye-bye I-95 (not to mention all of the cities it connects)!  I get the movie rights!   (And a creative director will ignore the part about millions of years).

 OK, back to reality.  Most (if not all) of us have heard of the Ring of Fire around the rim of the Pacific Ocean.  It is caused by spreading centers just like the ones we’ve been talking about that cause subduction zones, earthquakes and volcanoes that occur all the way around the Pacific.  Here’s a map (Wiki).  Note that all of the trenches shown are associated with subduction zones:

 shasta volcanic legacy.net ring of fire

 I’ve mentioned earthquakes, which, of course, are part of the whole scene.  Here’s a cross-section (similar to the one that I presented), but that focuses on the various types of earthquakes that happen around subduction zones (Wiki):

 shasta cross section wiki

The real doozies are the subduction zone quakes (up to Magnitude 9).  You can imagine the oceanic plate getting hung up, while stresses continue to build.  Then, the plate suddenly lets go . . .

 These are the type of quakes that might cause a sudden uplift of ocean floor, resulting in a tsunami.  And yes, this is exactly what occurred in Japan and Indonesia fairly recently.  Could it happen in the Pacific Northwest.  You bet.

 OK.  It’s time for some pictures.  Before we go to the mountain, it turns out that the McCloud River (my watershed river) has some beautiful waterfalls within 10 miles of my landing.  First, this Panoramio shot of the Upper McCloud Falls by Teton22:

 shasta upper mccloud falls pano teton22

Here’s a Panoramio shot of the Lower McCloud Falls by C. B. Cessna:

 shasta lower mccloud falls pano c.b.cessna

Now, let’s cast our gaze towards the mountain.  There are hundreds (thousands!) of photos for your perusal on line.  Basically, I was overwhelmed, and just picked up a few.

 I’ll start close to home (or I mean, close to landing) with a Panoramio shot by GoldPanner  taken along Route 89, which runs east-west just north of my landing.  This is the closest I could get of a landings-eye view of the mountain – and is the kind of view that most of us tourists would get (OK, without the motorcycle):

 shasta pano goldpanner

Staying local to my landing, here’s another Route 89 Panoramio shot, by Bruno Dere:

 shasta pano bruno dere

Here’s a fabulous shot by Kelsey Moty from Caliber Magazine:

 shasta caliber magazine kelsey moty

Here’s another from just about the same angle by Eric Cassano, posted in ShastaLake.com:

 shastalake.com eric cassano

For a different perspective, here’s a Panoramio shot by Dive Ken taken from the top of the mountain.  The pyramid (which is what he entitled his photo) is the mountain’s shadow!

 shasta pano sky dive ken

Instead of closing with yet another picture, I’ll close instead with this 1874 quote by John Muir:

“When I first caught sight of Mount Shasta over the braided folds of the Sacramento Valley, my blood turned to wine, and I have not been weary since.”

All in all, I think Mount Shasta is well worth a trip.

 That’ll do it.

 KS

 Greg

© 2013 A Landing A Day

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3 Responses to “Mount Shasta, California”

  1. buzzcreek said

    Reblogged this on How Come People are So Stupid? and commented:
    This is a fun way to just ‘drop in’ somewhere in the world and learn a LOT about the place. RANDOM.

  2. […] to wax geologic about the underlying mechanism that causes all of the Cascade volcanoes.  Click HERE to check out that […]

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