What Aren't We Seeing?

September 10, 2005 1:22 AM

What Aren't We Seeing? Panoramic (high-res) Photographs of Profound Geological Erosion.When we're in Monument Valley, it's tempting to say that we're looking at monuments - large hunks of stone scattered across the landscapes like statues to honor past heroes, or tombstones to honor the dead. A closer look tells us there's more to it than that. As we scan from one "monument" to the next, we can see in each monument a sloping base of roughly uniform vertical thickness and then straightsided rock of very uniform thickness. The rock is the same in all of them, suggesting that they were all part of two (or many more) uniform layers of stone that extended across the entire region. And how about here, where the Front Range and the Great Plains meet. Do you see a fault? An experienced geological observer would see a high ridge to the left with at most a few scattered ragged exposures of rock, whereas a prominent ridge of sedimentary rock juts up in the middle but is nowhere to be seen to the left. The road that we see going away from us on the left side of the image seems to separate two rather different areas. That observation provides us with a hypothesis: maybe there's a fault between two different kinds of rock. (more discussion here, and don't miss the Virtual Field Trip to a Major Unconformity).
posted by derangedlarid (21 comments total)

Also, don't miss the Web Gallery of Stone Buildings and Their Building Stone.
posted by derangedlarid at 1:53 AM on September 10, 2005

That last link is amazing- what a wonderful explanation of deduction through observation.
posted by pjern at 2:08 AM on September 10, 2005

solopsist: agreed.

We can nonetheless stand at this roadcut today, infer all these events of the past, and enjoy the vision of that ancient land.

Flagged as good. Thanks, (perhaps-not-so) derangedlarid
posted by jaronson at 2:39 AM on September 10, 2005

Thanks derangedlaird, that "also" link is fantastic.

I like Ship Rock.
posted by Dick Paris at 3:31 AM on September 10, 2005

As amazing as the discoveries are from the exploration of the far corners of our Solar System, this planet we live on offers up some jaw dropping sights to rival anything "out there".

Wow.
posted by Enron Hubbard at 3:50 AM on September 10, 2005

They're even more amazing to see in person. As I got closer and was spray-painting "F*ck You, Liberal Swine", I remember being just awestruck by the sheer size of these marvelous formations jutting out of the very ground my SUV was trying to traverse.
posted by hal9k at 5:29 AM on September 10, 2005

so lemme get this straight... the earth surface erodes at 1mm/year, 1km per million years.

Airliners fly at 11km, the x-prize was won flying up to 115km, so eg. our most recent direct ape ancestors walked in what is now sky, and dinosaurs walked in space?

whoah...

now that I got the ear of paleogeologists, is there a particular reason pangea is hypothesized to be only one landmass? This seems sorta bogus, the lack of distribution of oceans starting out.
posted by Heywood Mogroot at 5:29 AM on September 10, 2005

Niiiice find , that kind of content I'd like to see increasingly often...but brains are being chased away from the net :-(
posted by elpapacito at 5:44 AM on September 10, 2005

The American West is gorgeous. Because of a generally very dry climate, all the bones of the land show through. To hike down into the Grand Canyon is to walk back through almost two billion years of geologic time. Other canyons of the Colorado Plateau such as Zion and Bryce, are fascinating in the same way.

Recommended books:
The Roadside Geology series. Tells you what you're seeing out your car windows.

For Grand Canyon hikers: Dave Thayer's A Guide to Grand Canyon Geology Along the Bright Angel Trail. Whoops, sadly out of print, and the sole copy on Amazon is being sold at an absurd price.
posted by Slithy_Tove at 7:00 AM on September 10, 2005

Heywood Mogroot - For one, there are ranges of mountains in various places around the world that form into one continuous mountain range on Pangea. Also, the different continents you find the same fossils gives a clue that those places had to be linked by land somehow.

And just in the stratigraphy of the rocks themselves, the same layers of rocks found on different continents for the same time period can indicate that the continents were touching.

If you look at the dating and spreading rate of the mid oceanic rifts, you can count back to when they first ripped the supercontinent apart.

Here's some good diagrams of the fossil evidence and stratigraphy, and here's a neat click-through about the age of the Atlantic Ocean
posted by nile_red at 7:11 AM on September 10, 2005

re Pangaea:

I am not a geologist, nor do I play one on tv.

But ISTR that Pangaea wasn't the original uber-continent... apparently it isn't the case that In The Beginning there was Pangaea. It's more that for a moment, continental drift formed Pangaea, and that before that there was not Pangaea, and after that there was Laurasia and Gondwana.

The Appalachians, frex, are a mountain range formed by continental collisions before Pangaea formed.

Again, IIRC only. Is there a geologist in the house who knows if I do in fact R C'ly?
posted by ROU_Xenophobe at 9:23 AM on September 10, 2005

Best post I've read in a while. A good distraction on an otherwise grey day.

And yeah, Pangaea was just another phase of history.

Before Pangaea (which leads to the Paleomap Project)
posted by D.C. at 10:02 AM on September 10, 2005

I just want to add while I have a chance that the geologist, Bruce Railsback, who put all of this material together is one of the most original minds in science today. He has created, some might say invented, a new Periodic Table of the Elements by radically re-representing each element in a charged state rather than a neutral one like the traditional table. This non-neutral table, which he calls the Earth Scientist's Periodic Table and Their Ions, is threatening to bring about a quiet revolution in the way geo-chem is thought about and taught. The beauty of the chart is that it organizes the elements by charge, allowing them to appear on the chart in as many places and as many times as they do in the actual world. As a result the chart has these incredible banded groupings of charged atoms that one can see being distributed together into the same geo-chemical domain: for example water soluble ions found in rivers and the ocean are together, others that remain in the mantle of the earth forever are another band, still others that make up the dirt of the land, etc. It is a stunning achievement. Here is Railsback's intro to the new table, and a nice tutorial on the table itself.
posted by derangedlarid at 10:47 AM on September 10, 2005

No pun intended, by the way. Railsback's table happens to be truly radical.
posted by derangedlarid at 11:07 AM on September 10, 2005

thanks for this. the FPP links and those in the comments went straight to the 4th grader's homeschooling bookmarks files.
posted by RedEmma at 11:27 AM on September 10, 2005

The cool building stone site reminded me of the NIST stone test wall - 2352 individual samples of stone, of which 2032 are domestic stone from 47 states, and 320 are stones from 16 foreign countries
posted by roboto at 12:43 PM on September 10, 2005

roboto, very cool link. thanks, highly enjoyable.
posted by derangedlarid at 2:17 PM on September 10, 2005

Wow, a really amazing FPP, it led to a really fun lesson in geology.
posted by ddf at 2:22 PM on September 10, 2005

Amazing images, really nice mini-lesson on types of geologic layering. Thanks.
posted by emjaybee at 2:46 PM on September 10, 2005

Great post that will go in my bookmarks.
posted by bjgeiger at 2:54 PM on September 10, 2005

If you found this interesting, do look into John McPhee's brilliantly written, Pulitzer-Prize winning book, Annals of the Former World.
posted by driveler at 11:38 AM on September 11, 2005