# Geology Question: "Ribs" on the surface of the Earth (US Southwest) **URL:** \ **Category:** Factual Questions\ **Created:** [April 21, 2018, 12:12am UTC](https://boards.straightdope.com/t/geology-question-ribs-on-the-surface-of-the-earth-us-southwest/812833 "2018-04-21T00:12:16Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Tripler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripler/32/21807_2.png) [@Tripler](https://boards.straightdope.com/u/Tripler)\ **Post date:** [April 21, 2018, 12:12am UTC](https://boards.straightdope.com/t/geology-question-ribs-on-the-surface-of-the-earth-us-southwest/812833/1 "2018-04-21T00:12:16Z")
A recent co-worker reminded me of some of my drives through the local area. I had forgotten, but realized there are these earthen “ribs” around here, most prominent in some of the links below. I suspect they’re from ancient volcanic activity, but is is there a name for them? How were they formed? Set your Google Maps to “Terrain View” and zoom out. . . you’ll see what I mean. [South of Pie Town, NM](https://www.google.com/maps/place/34.2826531,-108.1356232) [NW of Pie Town, NM](https://www.google.com/maps/place/34.3816896,-108.0050155) [Up towards Ship Rock, NM](https://www.google.com/maps/place/36.664269,-108.858508) I thought they might be from glacial retreat, but isn’t New Mexico too far south for the glaciers to have reached? Tripler This post not funded by the Pie Town Tourism Board. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [April 21, 2018, 12:37am UTC](https://boards.straightdope.com/t/geology-question-ribs-on-the-surface-of-the-earth-us-southwest/812833/2 "2018-04-21T00:37:52Z")
i’m going to delete my stupid speculation on what they might be and just give my links to [the third one](https://www.google.com/maps/@36.6393367,-108.8261971,3a,75y,356.84h,79.24t/data=!3m7!1e1!3m5!1sK-UlrDgTi5rnl1o8texyyA!2e0!6s%2F%2Fgeo1.ggpht.com%2Fcbk%3Fpanoid%3DK-UlrDgTi5rnl1o8texyyA%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D317.28937%26pitch%3D0%26thumbfov%3D100!7i3328!8i1664!5m1!1e4) and the [first one](https://www.google.com/maps/@34.3074799,-108.1597373,3a,60y,194.46h,105.07t/data=!3m6!1e1!3m4!1sULYX6Nic9KlkmCcSWqMn2A!2e0!7i13312!8i6656!5m1!1e4) from Google Street view which provide a more up-close view of them. The third one definitely doesn’t look like glacial activity to me, but I’m not 100% sure on the first and I can’t find a good up-close view of the second. ---
**Author:** ![blondebear](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blondebear/32/1022_2.png) [@blondebear](https://boards.straightdope.com/u/blondebear)\ **Post date:** [April 21, 2018, 12:46am UTC](https://boards.straightdope.com/t/geology-question-ribs-on-the-surface-of-the-earth-us-southwest/812833/3 "2018-04-21T00:46:32Z")
Volcanic dikes, maybe? ---
**Author:** ![Ike\_Witt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ike_witt/32/283_2.png) [@Ike\_Witt](https://boards.straightdope.com/u/Ike_Witt)\ **Post date:** [April 21, 2018, 1:09am UTC](https://boards.straightdope.com/t/geology-question-ribs-on-the-surface-of-the-earth-us-southwest/812833/4 "2018-04-21T01:09:53Z")
I would guess it is what Monument Valley will look like in another couple million years. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [April 21, 2018, 10:00am UTC](https://boards.straightdope.com/t/geology-question-ribs-on-the-surface-of-the-earth-us-southwest/812833/5 "2018-04-21T10:00:56Z")
> [@blondebear](#): > > Volcanic dikes, maybe? Looks like that’s it, as [wikipedia’s entry](https://en.wikipedia.org/wiki/Dike_(geology)#/media/File:Minette_Dyke_in_New_Mexico_USA_01.jpg) on dikes has a picture of one of these near Shiprock! For some reason I thought that dikes were always vertical. ---
**Author:** ![pullin](https://avatars.discourse-cdn.com/v4/letter/p/c57346/32.png) [@pullin](https://boards.straightdope.com/u/pullin)\ **Post date:** [April 21, 2018, 12:06pm UTC](https://boards.straightdope.com/t/geology-question-ribs-on-the-surface-of-the-earth-us-southwest/812833/6 "2018-04-21T12:06:29Z")
In the southwest, isn’t this just the typical [Basin and Range](https://en.wikipedia.org/wiki/Basin_and_Range_Province) topography? Not a geologist, but that’s my guess. ---
**Author:** ![Tripler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripler/32/21807_2.png) [@Tripler](https://boards.straightdope.com/u/Tripler)\ **Post date:** [April 21, 2018, 1:29pm UTC](https://boards.straightdope.com/t/geology-question-ribs-on-the-surface-of-the-earth-us-southwest/812833/7 "2018-04-21T13:29:46Z")
> [@blondebear](#): > > Volcanic dikes, maybe? > [@Ludovic](#): > > Looks like that’s it, as [wikipedia’s entry](https://en.wikipedia.org/wiki/Dike_(geology)#/media/File:Minette_Dyke_in_New_Mexico_USA_01.jpg) on dikes has a picture of one of these near Shiprock! For some reason I thought that dikes were always vertical. Wow–thanks! Now I have an answer! > [@pullin](#): > > In the southwest, isn’t this just the typical [Basin and Range](https://en.wikipedia.org/wiki/Basin_and_Range_Province) topography? Not a geologist, but that’s my guess. I think it is–I can remember seeing some granite dikes in Nevada, out towards the Testing area, and I’ll take a look while I’m out there this week. I’m simply more familiar with New Mexico lately. Tripler Thanks!! Interesting. . . ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [April 21, 2018, 1:38pm UTC](https://boards.straightdope.com/t/geology-question-ribs-on-the-surface-of-the-earth-us-southwest/812833/8 "2018-04-21T13:38:44Z")
> [@Tripler](#): > > Set your Google Maps to “Terrain View” and zoom out. . . you’ll see what I mean. ‘Terrain View’? Never heard of it. There doesn’t appear to be such an option. All I see is ‘Map’ and ‘Satellite’. 😕 ---
**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:** [April 21, 2018, 3:23pm UTC](https://boards.straightdope.com/t/geology-question-ribs-on-the-surface-of-the-earth-us-southwest/812833/9 "2018-04-21T15:23:47Z")
> [@Ludovic](#): > > Looks like that’s it, as [wikipedia’s entry](https://en.wikipedia.org/wiki/Dike_(geology)#/media/File:Minette_Dyke_in_New_Mexico_USA_01.jpg) on dikes has a picture of one of these near Shiprock! For some reason I thought that dikes were always vertical. Dykes can be subvertical, the defining feature is that they cut across existing geology like sedimentary beds or other conformities. Just like sills don’t have to be horizontal, just parallel to existing bedding. Note that the Wiki [illustration of the difference](https://en.wikipedia.org/wiki/Sill_(geology)#/media/File:The_difference_between_a_sill_and_a_dike.jpg) even uses a subvertical dyke. ---
**Author:** ![Tripler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripler/32/21807_2.png) [@Tripler](https://boards.straightdope.com/u/Tripler)\ **Post date:** [April 21, 2018, 6:49pm UTC](https://boards.straightdope.com/t/geology-question-ribs-on-the-surface-of-the-earth-us-southwest/812833/10 "2018-04-21T18:49:24Z")
> [@Johnny\_L.A](#): > > ‘Terrain View’? Never heard of it. There doesn’t appear to be such an option. All I see is ‘Map’ and ‘Satellite’. 😕 Under ‘Map View’ there ought to be three little bars in the top left of your screen for “Menu.” Click that, and the dropdown _should_ have “Terrain” under ‘Satellite.’ Tripler It’s pretty helpful, that Terrain View. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [April 21, 2018, 10:29pm UTC](https://boards.straightdope.com/t/geology-question-ribs-on-the-surface-of-the-earth-us-southwest/812833/11 "2018-04-21T22:29:05Z")
nm ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [April 21, 2018, 10:52pm UTC](https://boards.straightdope.com/t/geology-question-ribs-on-the-surface-of-the-earth-us-southwest/812833/12 "2018-04-21T22:52:04Z")
> [@pullin](#): > > In the southwest, isn’t this just the typical [Basin and Range](https://en.wikipedia.org/wiki/Basin_and_Range_Province) topography? Not a geologist, but that’s my guess. > [@Tripler](#): > > I think it is–I can remember seeing some granite dikes in Nevada, out towards the Testing area, and I’ll take a look while I’m out there this week. I’m simply more familiar with New Mexico lately. Not really. “Basin and range” refers to topography on much larger scales. The basins and ranges, as the article says, appear to be due to lithospheric extension in the region. Basically the crust has been stretched out, resulting in faulting with upthrust ranges and downthrust basins. The ranges run parallel to one another, but are not straight lines, and are thousands of feet higher than the basins. These are clearly volcanic dikes, which mostly are a few tens of meters in height. Now volcanism in the region is related to its tectonic history, so there is a connection. But these features are much much smaller than the “ranges,” and are due to a different geological process. In fact, there aren’t any typical ranges visible near these features. The classic Basin and Range topography is mostly seen in Nevada and western Utah.