Perhaps it is difficult for non-geologists who are unfamiliar with the processes involved—but not so difficult for geologists who deal with the actual evidence on a daily basis.
We all have a tendency to rely on our uninformed intuition. Scientists rely on evidence.
See my quote from Bruthans et al. above - it explains it very easily - the arch is left standing because it has a stronger structure than the surrounding sandstone.
So far, nobody’s produced any evidence other than that of the rapid and catastrophic variety. Exactly what Oard has argued is responsible for producing the arches we have in nature. That’s why our supply of natural arches in the wild is steadily drying up:
Arches National Park has over 2,000 rock arches. Forty-three collapsed between 1970 and 2015. That gives a rate of collapse of about one per year, which means that all would be gone in about 2,000 years, at the prevailing rates of erosion from wind and rain.
You said that you didn’t appeal to changing the laws of Physics. My challenge to you is to demonstrate how some of the processes you invoke are compatible with the laws of Physics as we know them. I am certain that you cannot do that in the examples I raised. Whether or not you believe in the Bible has nothing to do with this.
Every mountain and every rock formation we see exposed on Earth is the product of weathering and erosion (ok, some very recent volcanoes excepted perhaps). These processes act far from uniformly and their effects are greatly dependent on variations in mineralogy, cementation, rock fabric, fracturing and faulting, local climate, base level, and much more. Arches are erosional remnants, just like the non-arched bits of rock around them, where much of the bedrock has been eroded away already but some bits are still standing. They weren’t always there and they will not last forever. As has been discussed above, arches can be formed by most types of weathering and erosion: wind, flowing water, waves and ice, and their formation can be relatively swift or relatively slow depending on all the factors I mentioned.
All in all I think they are of very little relevance when it comes to discussing the age of the Earth.
Just to remind everyone how PDPrice is running from the Catherine Creek Arch which was eroded by wind and rain out of basalt (i.e solidified lava) and not by any river, let alone a global Flood.
Description
This is a massive natural rock arch formed by eroding columnar basalt. It may be one of the largest arches in this area. Although it’s not entirely obvious from below, this is a true freestanding arch. Pole and rail fences above and below the arch keep visitors at a distance as this is a sacred site for Native Americans.
PDPrice’s continued evasion speaks volumes about his YEC “geology” ineptitude. 
The bottom line is the contrarian arguments are always about preaching to the non-geologist choir that needs reassurance that the “evil” scientists are wrong.
So it is ultimately fear based, thinking that to protect the Bible, one must do everything possible to protect one favorite brand of traditions and ignoring (but cherry-picking when possible) the scientific evidence ignored.
Wrong. That assumes all the arches are the same thickness, same strength, formed all at the same time, and are all undergoing the same erosion rate. It also incorrectly assumes no new arches are forming which is demonstrably false as the photos you’ve seen attest.
You might want to educate yourself on the history of the area and how the arches form in the first place. Or not.
A Story in Stone
The story of Arches begins roughly 65 million years ago. At that time, the area was a dry seabed spreading from horizon to horizon. If you stood in Devils Garden then, the striking red rock features we see today would have been buried thousands of feet below you, raw material as yet uncarved. Then the landscape slowly began to change.
First, geologic forces wrinkled and folded the buried sandstone, as if it were a giant rug and someone gathered two edges towards each other, making lumps across the middle called Anticlines. As the sandstone warped, fractures tore through it, establishing the patterns for rock sculptures of the future.
Next, the entire region began to rise, climbing from sea level to thousands of feet in elevation. What goes up must come down, and the forces of erosion carved layer after layer of rock away. Once exposed, deeply buried sandstone layers rebounded and expanded, like a sponge expands after it’s squeezed (though not quite so quickly). This created even more fractures, each one a pathway for water to seep into the rock and further break it down.
Today, water shapes this environment more than any other force. Rain erodes the rock and carries sediment down washes and canyons to the Colorado River. Desert varnish appears where water cascades off cliffs. In winter, snowmelt pools in fractures and other cavities, then freezes and expands, breaking off chunks of sandstone. Small recesses develop and grow bigger with each storm. Little by little, this process turns fractured rock layers into fins, and fins into arches. Arches also emerge when potholes near cliff edges grow deeper and deeper until they wear through the cliff wall below them. In addition to grand arches, water dissolves small honeycomb formations called tafoni.
Over time, the same forces that created these arches will continue to widen them until they collapse. Standing next to a monolith like Delicate Arch, it’s easy to forget that arches are impermanent. Yet the fall of Wall Arch in 2008 reminded us that this landscape continues to change. While some may fall, most of these arches will stand well beyond our lifetime: a lifetime blessed with an improbable landscape 65 million years in the making.
Erosion creates all sorts of gorges, pillars, and hoodoos. It is not difficult, actually, to imagine arches. There is no violation of physics here. You are trying to register a difficulty which does not exist. This is an argument ex nihilo.
That’s because the Young Earth Creationist community tends to deplore Uniformitarianism (under their non-standard definition) but happily embraces even imaginary uniform rates when it suits the debate of the moment.
This inconsistent “logic” was one of the many factors that led me out of Young Earth Creationism and “creation science.” I eventually accepted the historical record God clearly revealed in his creation and rejected the crumbling traditions of fallible man which had been irrationally imposed upon the Biblical text through equally inconsistent hermeneutics. (How could “Billions of dead things, buried in rock layers, laid down by water, all over the earth!” not embarrass me into reconsidering the YEC tradition under which I grew up?)
That’s assuming what is to be proved. Yes, erosion did produce those features–rapid erosion. Arches are eroding at a rate that is incompatible with gradualist claims about their origin.
If true, this shows your departure from YEC was never based on sound reasoning to begin with. What I am showing you here is not inconsistent logic. It’s called a reductio ad absurdum. I’m showing that the kind of thinking that uniformitarians use is self-defeating. Uniformitarians are forced to cherry pick the data to confirm the ‘ages’ they want to get. Measuring erosion rates is not how I arrive at my beliefs about the past.
Now to your point: you claim that erosion rates of arches that are measurable today are not uniform. That the idea we can extrapolate those rates backwards is “imaginary”. What do you base this on? You said you were looking at evidence. But I just showed you the evidence that these arches are disappearing far too quickly to have formed by gradualism. Your only response is this nonsensical handwaving?
ANSWER: The simple fact that such erosion rates are NOT uniform.
Now you are moving the goalposts. The request was for evidence of a slow natural process for arch formation, and I provided that. Do you accept that evidence?
The relatively rapid erosion of existing arches is a different question. Is that rate constant or is it accelerated by human activities? This also seems to imply there were many more arches in the not-too-distant past, which is reasonable since evidence of collapsed arches in Arches NP is pretty easy to find. (And another very nice place to visit!)
From Batten’s article:
The conditions that formed these arches do not prevail today, so no new arches are forming in the National Park. Again, this is consistent with the real history of the world from the Bible, with the arches forming under the special conditions that prevailed in the Flood or soon after.
Also, I have been unable to find any support for this claim:
Forty-three collapsed between 1970 and 2015.
(I did look.)
Good job refuting yourself in back to back sentences.
You didn’t show any such thing. You asserted it with zero supporting evidence as usual. You also ignored the actual geologic evidence of how the arches formed and are still forming.
How about the basalt Catherine Creek Arch? I’m sure you’ll ignore that too until long after the thread is locked and forgotten.
And the Golden Arches continue to multiply while eroding our society’s health (at an accelerating rate of gradualism not predicted by Uniformitarianism.)
This is from the U.S. Park Service on Arches National Park.
Water carried away sand grains one by one and widened the cracks into narrow canyons. Today, the thin rock walls between these canyons are called fins, because they look something like a fish’s fins. In cooler months, water in the form of rain and snow enters tiny cracks in the fins, freezes and expands, and causes little pieces of sandstone to flake off. After a long time, the tiny cracks break all the way through the fin and an arch is formed. Arches are still forming today, and many ages and sizes of arches are found throughout the park. How were arches formed? Over time, parallel fractures in surface rock eroded to form “fins.” As the process of erosion continued, arches were created where the fins were worn completely through.
A century of coastal erosion is neither rapid nor catastrophic.
Yes, weathering can account for arches, and in fact they are unavoidable. The same erosive processes which eventually collapse arches played a role in their making and replenishes them.
Hellmut H. Doelling - Geology of Arches National Park
Arches can form in many ways, but most in the park are the result of a combination of three peculiar features: the nature of the Entrada Sandstone sand grains, the susceptibility of the sandstone to weathering and erosion, and fractures in the sandstone that were created during the formation of anticlines. Most arches and fins at Arches National Park have formed wherever the Entrada Sandstone is arched over an anticline on which closely spaced paralleling fractures have developed
Natural Erosion of Sandstone as Shape Optimisation
Natural arches, pillars and other exotic sandstone formations have always been attracting attention for their unusual shapes and amazing mechanical balance that leave a strong impression of intelligent design rather than the result of a stochastic process. It has been recently demonstrated that these shapes could have been the result of the negative feedback between stress and erosion that originates in fundamental laws of friction between the rock’s constituent particles.
…
an arch forms when the original structure has two localized support points, causing stress concentrations. Weathering, abrasion and wind deflation removes the granular material in the regions subjected to relatively small compressive stresses, leaving more stressed and consolidated material intact, which, after many loops of erosion, leads to a distinctive natural arch structure.
Are you saying that the rate of rock erosion by natural forces has somehow come to be greatly increased in recent times as compared to ancient times? Why?
