Wall Arch before its collapse
(Photograph courtesy John Crossley, www.americansouthwest.net/)
(Wall Arch following its collapse, August 2008
(Photo by API National park Service)
No-one witnessed it's dramatic demise, but that is geology for you! A formation which to you and I may seem beautiful at this moment in time is merely a small step in the geological process of erosion back down to individual particles again, ready to be deposited elsewhere to begin the whole process all over.
So perhaps we need to enjoy spectacular features like these while they are here and not take them entirely for granted!
Double Arch, the Windows section, arches National Park, Utah.
(Photo courtesy John Crossley www.americansouthwest.net/)
Some features are more 'tunnel' than 'arch', such as this formation, aptly named 'Tunnel Arch'!
Fins near Courthouse Towers in the Windows Section of Arches National Park, Utah
(Photo courtesy John Crossley, www.americansouthwest.net/)
So how did the Arches form?
How on earth did these spectacular arches come to be? The formation of the amazing buttes at Monument Valley I can just about understand, but 1000+ arches in one area? So, a little reading was called for and this is what I found:-
Okay, around 300 million years ago the Colorado Plateau area as Ron Blakey's paleogeographical maps will show you, was ocean. With the passage of time and a great deal of evaporation, a huge salt bed was left behind. These salts were eventually overlain with sand sediments ultimately forming a sandstone layer over the salt bed. However, under pressure salt becomes unstable and the area became subject to distortion and buckling, forming domes and folds. Increasing pressure creates faulting which exposes the formations to the erosional effects of the elements, creating 'fins'. These in turn are eroded away such that in certain circumstances holes are created through them - the start of the formation of an 'arch'.
Okay, that may be a fairly simplistic explanation of their formation, but it at least gives you an idea. Fascinating though, don't you think? Just google 'Arches National Park Geology' if you want more details!
Now, any fellow English persons looking in may well be wondering quite what I have against the geology of good ol' Great Britain! Well, the answer is absolutely nothing and this is something I will start to rectify in future posts!
Cheers for now,