Monday, February 16, 2015

A Panorama of Geological History

When Roger and I went for a walk on Monday we noticed this sign on a part of the Hammond Trail we hadn't been on before.
I'll write here what the sign says in the lower left:
A Geologic Staircase--with Marine-Deposited Carpeting

Looking north towards Trinidad, you can see a sequence of abandoned marine terraces, or wave-cut platforms, rising inland from the sea in a roughly staircase formation.

Waves pound against the exposed shoreline cutting a vertical face over time. Wave action then planes smooth the sea floor at the base of the cliff, forming the flat surfaces of the next terrace ‘step.’ Marine sediments are deposited on the flat surfaces. These terraces rise up as the Gorda Plate thrusts under the North American Plate. They then become the vegetated, inhabited landscape you see today.

I wanted you to see what it's like to look to north from this point and see what this sign is talking about. I have been inspired by Mark P of CaniConfidimus to try to piece together a panorama, and this task was perfect. I haven't tried to do a panorama in years. This photo is three separate shots, showing Trinidad Head and Strawberry Rock, the abandoned seastack.

Trinidad Head is an erosion-resistant block of gabbro (similar to basalt in composition) in the Franciscan Complex bedrock— an assemblage of diverse rocks embedded in a soft matrix of sheared shale and serpentinite.

Strawberry rock, visible in the distance, is an abandoned, erosion-resistant seastack (composed of greenstone rock, a metamorphosed basalt), that rose with the surrounding land during periods of tectonic uplift. You can see present-day seastacks scattered along the coastline.

You have to click on the panorama and look to the right from Trinidad Head to see Strawberry Rock, and along the way notice those marine terraces. I've added the above close-up, in case you miss the rock. I think the interesting thing to consider when looking at a beautiful ocean landscape like this is the nearly unfathomable number of years it took to create this scene. And there, in a little rise is a formation so easily missed, a seastack:  a geological landform consisting of a steep and often vertical column or columns of rock in the sea near a coast, formed by erosion. Stacks are formed over time by wind and water, processes of coastal geomorphology.

There's nothing quite like getting my weight-bearing exercise while walking along this stunning expanse of ocean, and learning something new all at the same time. Yes!

UPDATED on Wednesday, February 18

I wondered if it might be possible to hike to Strawberry Rock, so I googled around and found this incredibly interesting site. The seastack is located in a 2nd growth redwood forest. This link will take you to a website that shows the efforts by locals to save that forest. More beautiful naked people laying their bodies down for the earth.

14 comments:

  1. Beautiful panorama. Just like being there. Amazing. Thank you for the geological history.

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  2. Great blog this week and good panarama shows everything nicely

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  3. like looking into space...we are looking back in time. I love the pano shot - nicely done!

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  4. Goodness that panorama shot is suitable for framing. Amazing what is seen when we look closely but more importantly, to know what we are seeing. Well done.

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  5. Interesting term, "abandoned"; thank you for the great information, too.

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  6. am-- Glad you liked the panorama. It was fun to try and make it look like what we were seeing.

    Loren-- Thank you!

    Bill-- Glad you liked this post and the panorama.

    Tara-- I love these wide open ocean views on a clear-sky day.

    Arkansas Patti-- Thank you so much for your kind words. It is wonderful to know what it is we are looking at.

    isabelita-- I had the same thought about the word "abandoned." Interesting in such a context.

    MandT-- Absolutely!

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  7. The pano shot when clicked is amazing. Excellent. I can see all of it. Very interesting. Thanks so much for your kind comment on my blog.

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  8. Have you felt earthquakes as the upper surface of the Gorda Plate scrapes along the lower surface of the North American Plate? So cool! We're pretty tectonically inert here in the northern Piedmont right now, but in the past, we've been front and center for some pretty stupendous tectonic fireworks. And, come to think of it, we DID feel the earthquake that occurred in northwest Virginia a few years ago that damaged the Washington Monument.

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  9. Nora-- So glad you like the panorama shot. It was fun to do.

    Scott-- I haven't felt an earthquake here (YET), but I'm certain if we stay, we'll definitely feel one. This is a very active part of the earthquake zone in California. Just the other day, I remembered the first earthquake I ever felt, it was a 6.7 on February 9, 1971 called the Sylmar quake. We had just moved to California from NJ a few months earlier. It was quite an impressive introduction to tectonics. Roger and I were together for the Loma Prieta quake on October 17, 1989. That was a 6.9. There is something about earthquakes that really give you sense of the power of the earth. Very cool that you felt one in Virginia.

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  10. I agree on the panorama. It really deserves clicking on to see the detail. Way back in undergrad school a geology teacher asked me if I could consider majoring in geology. I said no, but I've often wondered if that was a mistake.

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  11. Mark-- I am so glad that you liked the panorama. I use Photoshop, but not Elements, and it doesn't have the panorama feature. I tried to stitch the piece together, but I still see variations of blue in the sky where it just doesn't match. Geology would have been an interesting major.

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  12. Both interesting and beautiful...
    The panoramic photo is amazing!

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