# When was Arizona underwater? **URL:** \ **Category:** Factual Questions\ **Created:** [September 6, 2021, 1:38am UTC](https://boards.straightdope.com/t/when-was-arizona-underwater/950154 "2021-09-06T01:38:43Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [September 6, 2021, 1:38am UTC](https://boards.straightdope.com/t/when-was-arizona-underwater/950154/1 "2021-09-06T01:38:43Z")
Arizona has some amazing geology. It’s full of beautiful rock stack with horizontal stripes like this. [![](https://thumbs.dreamstime.com/z/massive-sandstone-pillars-soar-above-iconic-monument-valley-sunset-arizona-usa-53840131.jpg) ](https://thumbs.dreamstime.com/z/massive-sandstone-pillars-soar-above-iconic-monument-valley-sunset-arizona-usa-53840131.jpg) As far I understand, this was all once sea bed. The oceans deposited layer upon layer of sediment. The composition of sediment changed over time. This accounts for layers o0f different colour. The oceans receded. The sediment changed to rock. And then erosion wore most of the rock away, leaving a few stacks. Is that correct? Please fight my ignorance if I’ve misunderstood. Here’s the thing I don’t understand. Most of Arizona is a long way from the coast, and 4,000 feet above current sea level. Even in Pangea, the land that is currently Arizona was a long way from the coast. So when, and how, was it ever sea bed? Did ancient oceans rise more than 4,000 feet above current levels? Was Arizona once at a lower elevation, but has been pu8shed upwards from underneath? Some other thing I haven’t thought of? ---
**Author:** ![Babale](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/babale/32/15666_2.png) [@Babale](https://boards.straightdope.com/u/Babale)\ **Post date:** [September 6, 2021, 1:44am UTC](https://boards.straightdope.com/t/when-was-arizona-underwater/950154/2 "2021-09-06T01:44:11Z")
Wikipedia has a breakdown of how the seas came and went, but most recently Arizona was part of the Western Interior Seaway. > **[Paleontology in Arizona](https://en.m.wikipedia.org/wiki/Paleontology_in_Arizona)** > > Pages for logged out editors learn more > > Paleontology in Arizona refers to paleontological research occurring within or conducted by people from the U.S. state of Arizona. The fossil record of Arizona dates to the Precambrian. During the Precambrian, Arizona was home to a shallow sea which was home to jellyfish and stromatolite-forming bacteria. This sea was still in place during the Cambrian period of the Paleozoic era and was home to brachiopods and trilobites, but it withdrew during t... ---
**Author:** ![GreysonCarlisle](https://avatars.discourse-cdn.com/v4/letter/g/a87d85/32.png) [@GreysonCarlisle](https://boards.straightdope.com/u/GreysonCarlisle)\ **Post date:** [September 6, 2021, 1:53am UTC](https://boards.straightdope.com/t/when-was-arizona-underwater/950154/3 "2021-09-06T01:53:57Z")
Pretty good timeline [here](http://janrasmussen.com/pdfs/geol_hist_az_Rasmussen_2012%20preprint.pdf), starting on page 5. PDF warning. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [September 6, 2021, 7:06am UTC](https://boards.straightdope.com/t/when-was-arizona-underwater/950154/4 "2021-09-06T07:06:17Z")
> [@Peter\_Morris](#): > > As far I understand, this was all once sea bed. The oceans deposited layer upon layer of sediment. Actually, a lot of the sandstone in Monument Valley and Canyonlands (certainly, the most impressive buttes and mesas) _isn’t_ marine, but aeolian. Fossilized dunes, basically. Much of the rest is river sandbar and alluvial fan deposits, and then the rest is delta and coastal sandbar sands. Generally, when you have a lot of reddish-orangish sandstone, it’s not primarily marines, but terrestrial. ---
**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\ **Post date:** [September 6, 2021, 7:41am UTC](https://boards.straightdope.com/t/when-was-arizona-underwater/950154/5 "2021-09-06T07:41:19Z")
What is the difference between those remaining “stacks” and the eroded flat part? Are those vulcanic vents perhaps? ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [September 6, 2021, 10:43am UTC](https://boards.straightdope.com/t/when-was-arizona-underwater/950154/6 "2021-09-06T10:43:38Z")
No, they’re sandstone. They’re just all that gets left after everything in between is eroded away. The difference is generally that the remanant parts were the bits between jointing that developed during various geological processes. The bits in the joints were easier to [weather](https://en.wikipedia.org/wiki/Weathering#Physical_weathering) and [erode](https://en.wikipedia.org/wiki/Erosion), so that’s where water channels preferentially developed and wind and ice and salt did most of its work. Here are some related papers with [nice](https://link.springer.com/article/10.1007/s12371-018-0339-3) [illustrations](https://www.sciencedirect.com/science/article/pii/S0169555X20302804) of the concept (from your part of the globe, even). Generally, volcanic remnants don’t form that characteristic mesa shape - look at [Shiprock](https://en.wikipedia.org/wiki/Shiprock), [Chaistla Butte](https://en.wikipedia.org/wiki/Chaistla_Butte), [Agathlan](https://en.wikipedia.org/wiki/Agathla_Peak) or even Bear Lodge Butte (Devils Tower). You do sometimes get something similar with [flood basalts](https://en.wikipedia.org/wiki/Flood_basalt), though. But the rock itself looks completely different. ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [September 6, 2021, 1:05pm UTC](https://boards.straightdope.com/t/when-was-arizona-underwater/950154/7 "2021-09-06T13:05:05Z")
> [@MrDibble](#): > > Actually, a lot of the sandstone in Monument Valley and Canyonlands (certainly, the most impressive buttes and mesas) _isn’t_ marine, but aeolian. Fossilized dunes, basically. Ah, that makes sense. ---
**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\ **Post date:** [September 6, 2021, 1:26pm UTC](https://boards.straightdope.com/t/when-was-arizona-underwater/950154/8 "2021-09-06T13:26:44Z")
Thanks for the information, I guessed completely wrong. On the other hand, that would have been a lot of volcanoes in a very small space. ETA: Nice pictures indeed, I should visit that Elbsteingebirge. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [September 6, 2021, 1:41pm UTC](https://boards.straightdope.com/t/when-was-arizona-underwater/950154/9 "2021-09-06T13:41:38Z")
December 8, 1941 ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [September 6, 2021, 1:42pm UTC](https://boards.straightdope.com/t/when-was-arizona-underwater/950154/10 "2021-09-06T13:42:41Z")
Took me a while 😃 ---
**Author:** ![Just\_Asking\_Questions](https://avatars.discourse-cdn.com/v4/letter/j/ba9def/32.png) [@Just\_Asking\_Questions](https://boards.straightdope.com/u/Just_Asking_Questions)\ **Post date:** [September 6, 2021, 2:09pm UTC](https://boards.straightdope.com/t/when-was-arizona-underwater/950154/11 "2021-09-06T14:09:07Z")
> [@Little\_Nemo](#): > > December 8, 1941 Too soon.