# Deepest canyon **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [December 14, 2019, 8:05pm UTC](https://boards.straightdope.com/t/deepest-canyon/844866 "2019-12-14T20:05:59Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [December 14, 2019, 8:05pm UTC](https://boards.straightdope.com/t/deepest-canyon/844866/1 "2019-12-14T20:05:59Z")
News reports such as [this one](https://www.sciencemag.org/news/2019/12/antarctic-video-reveals-deepest-canyon-earth) say they’ve found the deepest canyon on Earth under the Antarctic ice. Its name is Denman Canyon. Well, technically I suppose they’re right, but only because the canyon is filled with ice, so there’s no water there. When the ice melts (note I said ‘when’ not ‘if’) that canyon is going to fill with water and it’ll just be a deep inlet of the sea. There’s a couple other fairly deep canyons in the video at the above site and they’ll do the same thing. Anyway, calling it the deepest canyon is a tad misleading. ---
**Author:** ![Telperion](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telperion/32/509_2.png) [@Telperion](https://boards.straightdope.com/u/Telperion)\ **Post date:** [December 14, 2019, 8:48pm UTC](https://boards.straightdope.com/t/deepest-canyon/844866/2 "2019-12-14T20:48:06Z")
> [@dtilque](#): > > Well, technically I suppose they’re right, but only because the canyon is filled with ice, so there’s no water there. When the ice melts (note I said ‘when’ not ‘if’) that canyon is going to fill with water and it’ll just be a deep inlet of the sea. There’s a couple other fairly deep canyons in the video at the above site and they’ll do the same thing. Anyway, calling it the deepest canyon is a tad misleading. I don’t know that we can be sure about that. It looks to me like the ground around it is mostly above sea level, and that’s with a couple miles of ice on top of it, so the canyon might well end up on dry land at some point. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [December 14, 2019, 9:58pm UTC](https://boards.straightdope.com/t/deepest-canyon/844866/3 "2019-12-14T21:58:48Z")
Antarctica is currently being pushed down by the weight of the ice sheet. If that melted, the [whole continent would rise](https://en.wikipedia.org/wiki/Post-glacial_rebound). (No idea by how much, and how much that would be canceled out by rising sea levels.) ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [December 15, 2019, 12:20am UTC](https://boards.straightdope.com/t/deepest-canyon/844866/4 "2019-12-15T00:20:41Z")
> [@Telperion](#): > > I don’t know that we can be sure about that. It looks to me like the ground around it is mostly above sea level, and that’s with a couple miles of ice on top of it, so the canyon might well end up on dry land at some point. Then it’ll be a lake. Yes, there’ll be post-glacial rebound, but I would not expect 3500 meters of it so it should be still below sea level. But no matter how much rebound, it’ll still be a depression because the land around it will rebound too. And that depression will fill with water. ---
**Author:** ![Telperion](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telperion/32/509_2.png) [@Telperion](https://boards.straightdope.com/u/Telperion)\ **Post date:** [December 15, 2019, 12:59am UTC](https://boards.straightdope.com/t/deepest-canyon/844866/5 "2019-12-15T00:59:25Z")
> [@dtilque](#): > > Then it’ll be a lake. > > Yes, there’ll be post-glacial rebound, but I would not expect 3500 meters of it so it should be still below sea level. But no matter how much rebound, it’ll still be a depression because the land around it will rebound too. And that depression will fill with water. My understanding is that Antarctica would be a giant desert if it wasn’t covered in ice. Other than freezing cold there’s nothing to keep water from running through the soil, and global warming has a long way to go before anything much will grow there. ---
**Author:** ![PastTense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pasttense/32/14550_2.png) [@PastTense](https://boards.straightdope.com/u/PastTense)\ **Post date:** [December 15, 2019, 1:45am UTC](https://boards.straightdope.com/t/deepest-canyon/844866/6 "2019-12-15T01:45:03Z")
> [@dtilque](#): > > Well, technically I suppose they’re right, but only because the canyon is filled with ice, so there’s no water there. No. There are lots of canyons in the ocean–which is filled with water, for example: > **[Chesapeake Quarterly Volume 14 Number 3: The Grand Canyons off Our Coast](https://www.chesapeakequarterly.net/V14N3/main1/)** > > It was back in 1981 when scientists caught an early glimpse of the extraordinary sea life dwelling at the bottom of Baltimore Canyon. A diversity of coral and other surprising sea life species hide in deep gorges in the Mid-Atlantic. Chesapeake... ---
**Author:** ![Flyer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/flyer/32/7298_2.png) [@Flyer](https://boards.straightdope.com/u/Flyer)\ **Post date:** [December 15, 2019, 3:22am UTC](https://boards.straightdope.com/t/deepest-canyon/844866/7 "2019-12-15T03:22:48Z")
> [@Telperion](#): > > My understanding is that Antarctica would be a giant desert if it wasn’t covered in ice. Other than freezing cold there’s nothing to keep water from running through the soil, and global warming has a long way to go before anything much will grow there. There’s no “would be” about it. It IS a desert. Precipitation or lack thereof is what makes a desert. Heat has nothing to do with it. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [December 15, 2019, 3:27am UTC](https://boards.straightdope.com/t/deepest-canyon/844866/8 "2019-12-15T03:27:35Z")
> [@Telperion](#): > > My understanding is that Antarctica would be a giant desert if it wasn’t covered in ice. Other than freezing cold there’s nothing to keep water from running through the soil, and global warming has a long way to go before anything much will grow there. After the ice melts, it will indeed take a long time for plants to grow there. But not because the melt water immediately runs off through the soil. The Antarctic soil won’t be that porous and there’ll be clays form in it. Clays are generally non-porous. At any rate, most of the melt water will run off over the top of the ground, but there’ll be so much that that won’t matter. Based on how N American glaciers melted 11000 years ago, expect huge melt water lakes around the glaciers and some great floods when some obstacle to them flowing away is breeched or overtopped. > [@PastTense](#): > > No. There are lots of canyons in the ocean–which is filled with water, for example: > [Chesapeake Quarterly Volume 14 Number 3: The Grand Canyons off Our Coast](https://www.chesapeakequarterly.net/V14N3/main1/) It’s currently under a lot of ice so it was assumed by the writers of that paper that the ice went all the way down to the ground. Which would technically make the canyon dry land. But I wouldn’t be at all surprised if there’s currently some water at the bottom there. Quite the opposite, actually. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [December 15, 2019, 5:29am UTC](https://boards.straightdope.com/t/deepest-canyon/844866/9 "2019-12-15T05:29:06Z")
> [@Flyer](#): > > There’s no “would be” about it. It IS a desert. > > Precipitation or lack thereof is what makes a desert. Heat has nothing to do with it. It’s a desert now, but that’s because it’s covered in 3 to 4 km of ice. The combination of cold and altitude cause any water vapor in the wind blowing over the continent to condense and snow out near the coasts. I don’t think anyone can say what the climate there will be like once the ice all melts. But there will be massive quantities of melt water and any depression is going to be filled with it.