# Mountains, Trenches and Plate Tectonics **URL:** \ **Category:** Factual Questions\ **Created:** [February 8, 2006, 3:01am UTC](https://boards.straightdope.com/t/mountains-trenches-and-plate-tectonics/343493 "2006-02-08T03:01:11Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [February 8, 2006, 3:01am UTC](https://boards.straightdope.com/t/mountains-trenches-and-plate-tectonics/343493/1 "2006-02-08T03:01:11Z")
My son (btw, he insists that his user name is Fluffy Fang; Dad is speechless) is working on a science fair project and has a question: “you know how when 2 of the earths plates colide, they either make mountains, trenches or faults. what are the types of plates called? p.s. speling iz mi bect subgect!” He wants the name for plate boundaries that cause trenches vs. the boundaries that result in mountains. I am not familiar with any specific names to differentiate the two. I’m not sure what types of plates he is talking about. I’m familiar with subduction trenches, and with convergent, divergent and transverse boundaries but nothing that makes that distinction. I know that this sounds like a “Do your own homework” thread, but this is for the science fair and isn’t for credit. Also, his books are at Mom’s and he is here doing the project. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [February 8, 2006, 3:21am UTC](https://boards.straightdope.com/t/mountains-trenches-and-plate-tectonics/343493/2 "2006-02-08T03:21:13Z")
Here’s a nifty site with explanations and diagrams and all that… > [@](#): > > There are 3 primary types of Tectonic Plate boundaries: Divergent boundaries; Covergent boundaries; and Transform boundaries. > > SOURCE: [http://www.platetectonics.com/book/page\_5.asp](http://www.platetectonics.com/book/page_5.asp) ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [February 8, 2006, 3:29am UTC](https://boards.straightdope.com/t/mountains-trenches-and-plate-tectonics/343493/3 "2006-02-08T03:29:43Z")
“Covergent boundaries” above is misspelled and should be “Convergent boundaries”. Looking more at the linked site it seems a perfect one stop shop for your son’s project. It is nicely done and laid out, informative without overwhelming technical bits…good stuff. ---
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [February 8, 2006, 5:26am UTC](https://boards.straightdope.com/t/mountains-trenches-and-plate-tectonics/343493/4 "2006-02-08T05:26:32Z")
Thanks, **Whack-a-Mole**. It turns out that he was thinking of ocean and continental plates. He’s asleep, but I’ll let him know about that site in the morning. ---
**Author:** ![Whifton\_Polekitty](https://avatars.discourse-cdn.com/v4/letter/w/97f17d/32.png) [@Whifton\_Polekitty](https://boards.straightdope.com/u/Whifton_Polekitty)\ **Post date:** [February 8, 2006, 7:39am UTC](https://boards.straightdope.com/t/mountains-trenches-and-plate-tectonics/343493/5 "2006-02-08T07:39:49Z")
> [@cornflakes](#): > > Thanks, **Whack-a-Mole**. It turns out that he was thinking of ocean and continental plates. He’s asleep, but I’ll let him know about that site in the morning. You may want to gently remind the lad that trenches (such as the mid-oceanic variety) are not formed by plates colliding, but rather being pushed apart by new material coming up from the MOLTEN BOWELS OF THE VERY EARTH and pushing the plate along in a strange, constant birth. We call these divergent plate boundaries. ---
**Author:** ![Doobieous](https://avatars.discourse-cdn.com/v4/letter/d/da6949/32.png) [@Doobieous](https://boards.straightdope.com/u/Doobieous)\ **Post date:** [February 8, 2006, 8:12am UTC](https://boards.straightdope.com/t/mountains-trenches-and-plate-tectonics/343493/6 "2006-02-08T08:12:56Z")
> [@Whifton\_Polekitty](#): > > You may want to gently remind the lad that trenches (such as the mid-oceanic variety) are not formed by plates colliding, but rather being pushed apart by new material coming up from the MOLTEN BOWELS OF THE VERY EARTH and pushing the plate along in a strange, constant birth. We call these divergent plate boundaries. Maybe I’m missing something here, but trenches are formed when oceanit crust is pushed under lighter continental crust, or when one plate just slips underneath another, like the Marianas. The Middle America trench follows South America up into Mexico, and mountains have formed opposite the trench as well. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [February 8, 2006, 8:54am UTC](https://boards.straightdope.com/t/mountains-trenches-and-plate-tectonics/343493/7 "2006-02-08T08:54:06Z")
> [@Whifton\_Polekitty](#): > > You may want to gently remind the lad that trenches (such as the mid-oceanic variety) are not formed by plates colliding, but rather being pushed apart by new material coming up from the MOLTEN BOWELS OF THE VERY EARTH and pushing the plate along in a strange, constant birth. We call these divergent plate boundaries. Are you sure you’re not talking about mid-oceanic _ridges_? ---
**Author:** ![Gymnopithys](https://avatars.discourse-cdn.com/v4/letter/g/fbc32d/32.png) [@Gymnopithys](https://boards.straightdope.com/u/Gymnopithys)\ **Post date:** [February 8, 2006, 6:23pm UTC](https://boards.straightdope.com/t/mountains-trenches-and-plate-tectonics/343493/8 "2006-02-08T18:23:52Z")
Plate tectonics may not be fashionable anymore, see: [http://www.expanding-earth.org/](http://www.expanding-earth.org/) [http://www.geocities.com/CapeCanaveral/Launchpad/8098/Other.htm](http://www.geocities.com/CapeCanaveral/Launchpad/8098/Other.htm) [http://www.4threvolt.com/index.html](http://www.4threvolt.com/index.html) [http://www.4threvolt.com/Papers.html](http://www.4threvolt.com/Papers.html) [http://www.4threvolt.com/files/McCarthy2005.pdf](http://www.4threvolt.com/files/McCarthy2005.pdf) and many others ---
**Author:** ![Tapioca\_Dextrin](https://avatars.discourse-cdn.com/v4/letter/t/3d9bf3/32.png) [@Tapioca\_Dextrin](https://boards.straightdope.com/u/Tapioca_Dextrin)\ **Post date:** [February 8, 2006, 6:37pm UTC](https://boards.straightdope.com/t/mountains-trenches-and-plate-tectonics/343493/9 "2006-02-08T18:37:27Z")
> [@Gymnopithys](#): > > and many others these others also condider tin foil hats to be the height of fashion … ---
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [February 9, 2006, 2:56am UTC](https://boards.straightdope.com/t/mountains-trenches-and-plate-tectonics/343493/10 "2006-02-09T02:56:55Z")
> [@Whifton\_Polekitty](#): > > You may want to gently remind the lad that trenches (such as the mid-oceanic variety) are not formed by plates colliding, but rather being pushed apart by new material coming up from the MOLTEN BOWELS OF THE VERY EARTH and pushing the plate along in a strange, constant birth. We call these divergent plate boundaries. i agree with Doobieous about how ocean trenches are formed. i’ve recently studied how the marianas trench formed and i think it was made by plates colliding, not separating. thanks for the help though. –Fluffy Fang ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [February 9, 2006, 10:17am UTC](https://boards.straightdope.com/t/mountains-trenches-and-plate-tectonics/343493/11 "2006-02-09T10:17:41Z")
**Gymnopithys** - those links remind me of a guy going by the name of **Novagaea** I bumped into on another (now defunct) board; it was his assertion that the earth was once very much smaller and that the landmasses joined together to cover the entire surface seamlessly; within recorded human history though, the core burst out of the Earth (through what is now the Pacific ocean floor) and became the moon; the cataclysm also caused the crust to inflate to its present-day size, filled not with magma, but with superheated steam and plasma. That the coastlines of the landmasses are not like the edges of a jigsaw puzzle (i.e. the landmass carries on existing under the sea) was a distinction lost on him, as was any discussion of experiments concluding that the earth is not in fact an inflated balloon. He disappeared for a while, then came back with some weird pattern-finding stuff, where he argued (again, based on arbitrary examination of coastlines) that identical terrain features existed in multiple, different locations on Earth, because when the earth inflated, it did so by means of the surface delaminating like several layers of onion skin, and sliding, completely intact, over each other to their new locations. It’s sometimes disturbing just how disconnected from reality people can become. ---
**Author:** ![Gymnopithys](https://avatars.discourse-cdn.com/v4/letter/g/fbc32d/32.png) [@Gymnopithys](https://boards.straightdope.com/u/Gymnopithys)\ **Post date:** [February 9, 2006, 11:13am UTC](https://boards.straightdope.com/t/mountains-trenches-and-plate-tectonics/343493/12 "2006-02-09T11:13:04Z")
> [@Tapioca Dextrin](#): > > these others also condider tin foil hats to be the height of fashion … All of’em uneducated dunces, of course ☹ ---
**Author:** ![paperbackwriter](https://avatars.discourse-cdn.com/v4/letter/p/53a042/32.png) [@paperbackwriter](https://boards.straightdope.com/u/paperbackwriter)\ **Post date:** [February 9, 2006, 6:17pm UTC](https://boards.straightdope.com/t/mountains-trenches-and-plate-tectonics/343493/13 "2006-02-09T18:17:22Z")
No, not all. There’s a sprinkling of the totally bonkers, a few that occupy some other reality, and one or two that have completely and utterly crazy ideas that just happen to be right. Note, however, that the last category tends to be a very small minority. There’s just no evidence for this guy’s Velikovskian ideas about an inflated earth, and a huge amount of evidence against it. Seismicity, for one example OTTOMH, would be completely different if the Earth was filled with steam and plasma instead of mantle.