Is the Grand Canyon A Rift System.

[MrGamma]

I have studied the Grand Canyon a little bit and throughout my research many people referenced the creation of the canyon to have formed primarily via river erosion.

 

While I do not doubt that a river has eroded the walls of the canyon I do not believe it is responsible for it's great expanse.

 

Searching the USGS earthquake database I found the following information regarding the total amount of earthquakes having been recorded since the seventies. The grand canyon has by far the greatest ocurrances of earthquakes which suggests it has the greatest potential for tectonic movement.

 

The Grand Canyon

36.3N

-113W

300km radius 936 quakes

500km radius 9860 quakes

 

Red Rock Canyon Alberta

51.8N

-115.3W

300km radius 82 quakes

500km radius 334 quakes

 

Bryce Canyon

52.1

-115.3

300km radius 77 quakes

500km radius 242 quakes

 

Black Canyon

37.5

-112.4

300km radius 733 quakes

500km radius 4013 quakes

 

Kings Canyon

34.4

-106.8

300km radius 117 quakes

500km radius 388 quakes

 

Nahanni Four Canyons

62.3

-125.2

300km radius 218 quakes

500km radius 269 quakes

 

 

These arrows help illustrate the regions of the canyon which are rifting apart and thus cracking at the seams.

 

 

Using a map available for download from the USGS... http://pubs.usgs.gov/imap/i-2688/

 

I have added arrows along a major fault line which match up with some of the cracks.

 

 

Additionally this image illustrates a horst graben pattern

 

 

I am interested in your criticisms.

[iNow]

There was something about the rain that fell during the time... something like acid rain, that disolved the rock and limestone. It was water, not just erosion from flowing rivers, but a chemical reaction that made the rock disolve. I'll be damned if I can find the link, but I think I saw it on NOVA.

[MrGamma]

There was something about the rain that fell during the time... something like acid rain, that disolved the rock and limestone. It was water, not just erosion from flowing rivers, but a chemical reaction that made the rock disolve. I'll be damned if I can find the link, but I think I saw it on NOVA.

 

 

Yes... I have looked into the erosion aspect of this as well.

 

"Age and Evolution of the Grand Canyon Revealed by U-Pb Dating of Water Table-Type Speleothems"

 

http://www.sciencemag.org/cgi/content/abstract/319/5868/1377

 

This particular study says,

 

"Samples in the western Grand Canyon yielded apparent water table decline rates of 55 to 123 meters per million years over the past 17 million years"

 

"in contrast to eastern Grand Canyon samples that yielded much faster rates (166 to 411 meters per million years)"

 

 

The argument for a certain type of acid water eroding the rock faster would have to also support a different type of rock in the Western Canyon vs the East Canyon or at the very least a mechanism capable of sustaining different erosion rates over a 17 million year period.

 

 

Perhaps the water table levels are un-even due to a rift system which tore the land apart beginning at the East End. Rather than the water eroding the different ends of the canyon at different rates. Perhaps the land rifted apart at different rate.

 

If you will allow me to speculate and provide a visual comparison to how a rift system might split the land and drop water table levels at different rates I offer this.

 

"Taiwan's 'Grand Canyon' — a creation of the 921 Earthquake"

http://www.chinapost.com.tw/travel/taiwan%20central/taichung/2008/01/24/140421/Taiwan's-'Grand.htm

[insane_alien]

the grand canyon displays all the hallmarks of water erosion. you can even see some arches way way up the wall of the canyon in some places, rift valleys don't have this. compare it with the african rift valley, it is shallower, a depression rather than a more crack like valley.

 

its not a rift

[MrGamma]

the grand canyon displays all the hallmarks of water erosion. you can even see some arches way way up the wall of the canyon in some places, rift valleys don't have this. compare it with the african rift valley, it is shallower, a depression rather than a more crack like valley.

 

its not a rift

 

 

Sir... I do not doubt that the Grand Canyon was at one point under water. The fossil record trapped in the sedimentary layers is evidence of this.

 

The Kaibab Limestone being the youngest of the sedimentary layers contains brachiopods, coral, mollusks, sea lilies, worms and fish teeth fossils.

 

The Grand Canyon does share features with rift systems. Volcanism, Horst Grabens and Faults.

 

I would like to point out that the depth of the rift is irrelevant to whether or not tectonic forces and faults have created divergent boundaries.

 

The Great African Rift.

Ranges in elevation from c.1,300 ft (395 m) below sea level (the Dead Sea) to c.6,000 ft (1,830 m) above sea level in S Kenya.

 

The Grand Canyon

South Rim (about 7000 feet above sea level)

North Rim (about 8000 feet above sea level)

Inner Gorge (about 2000 feet above sea level)

 

Additionally they share approximately the same crustal thickness of 30km for the most part.

 

And on average the depth of the Grand Canyon is about 1600 meters while the African Rift includes some of the deepest lakes in the world (up to 1,470 meters deep at Lake Tanganyika).

 

 

I do not see where you have made the connection between rift systems having to be "shallower". If you could please explain this in detail I would be more inclined to accept your reasoning.

 

 

In any event, I am not blind to the fact that water table levels have etched themselves in the side of the canyon walls and produced some levels of erosion. I am only suggesting that the expanse of the canyon and the complex network of cracks which co-incide with fault lines make the Grand Canyon a rift system first and a drainage system second.

 

 

Edited September 28, 2008 by MrGamma

[iNow]

The limestone literally disolved as the water passed over it. Explained fine already. Prove first how the existing formation theory is bunk and I'd be more inclined to look at others.

[MrGamma]

The limestone literally disolved as the water passed over it. Explained fine already. Prove first how the existing formation theory is bunk and I'd be more inclined to look at others.

 

Sir... I am not suggesting the current theory of water erosion is bunk.

 

I am raising awareness to the...

 

Rift like cracks

Horst Graben patterns

Hundreds upon thousands of fault lines ( old and new )

Volcanoes

 

and the uneven water table levels which are an inexplainable reality should water erosion be the sole method of the Canyon's formation.

 

 

The current theory holds truth. But there is an underlying mechanism which cannot be ignored.

 

 

If you will allow me to elaborate on the potential for earth quake activity in this region using old fault lines as evidence for pre modern scientific tectonic activity and the current number of recorded earthquakes within a 30 year time span.

 

( 9860 earthquakes / 30 years ) x 17 million years = 5.58733333 × 10⁹ earthquakes. ( rough estimate )

[Baby Astronaut]

I see what you're saying, MrGamma. A few of the small jagged points look alike (especially the right-most arrow on each image), and the layouts are highly similar to one another, like when people first noticed the Americas would fit neatly at Europe and western Africa.

 

If all you're saying is that yes, water has eroded the surface rock, but the widening has been mostly the work of tectonic activity (giving credit to both) -- then I believe you're onto something.

Edited October 4, 2008 by Baby Astronaut

[JohnB]

MrGamma, while I see your point, there are a few things lacking.

 

If the Grand Canyon was in fact a techtonic rift area, then would we not see evidence of magma? Two parts of a plate can't spread without magma coming up to fill the gap.

 

Also, unless the Earth is getting bigger, then there must ba an associated subduction zone, where is it?

 

A simpler hypothesis is that the plate is not moving apart, but bending giving rise to fractures that do not penetrate too far down.

 

Just my 2c.

[dirtyamerica]

This is a pretty good discussion.

 

I thought the GC was created not only through erosion but also because of a massive upheaval dome.

 

Although it does make you wonder why the North and South rims are so different in altitude.