# What are the mechanics behind this landslide?

**URL:** <https://boards.straightdope.com/t/what-are-the-mechanics-behind-this-landslide/718276>\
**Category:** Factual Questions\
**Created:** [April 22, 2015, 11:31am UTC](https://boards.straightdope.com/t/what-are-the-mechanics-behind-this-landslide/718276 "2015-04-22T11:31:53Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\
**Post date:** [April 22, 2015, 11:31am UTC](https://boards.straightdope.com/t/what-are-the-mechanics-behind-this-landslide/718276/1 "2015-04-22T11:31:53Z")

</div>

I’ve just seen [this video](https://www.youtube.com/watch?feature=player_embedded&v=1gSDgZaHvtg) of a slow landslide in Russia and I’m wondering how it’s caused? Is it the snow and ice melting and moving the earth around it?

---

<div class="post-metadata">

**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\
**Post date:** [April 22, 2015, 11:54am UTC](https://boards.straightdope.com/t/what-are-the-mechanics-behind-this-landslide/718276/2 "2015-04-22T11:54:00Z")

</div>

Reminds me of [this slow-motion avalanche](https://www.youtube.com/watch?v=f5waSw2mMfY) in Italy (slows down after about 1:30).

If something is moving at a constant speed, whether slow or fast, then the forces on it sum to zero. In either of these cases, there appear to be large portions of the flow that are on flat or shallow-sloping ground, and these are being pushed forward by whatever portion is further uphill on a steeper slope (in your video there are moments where you can get a glimpse of the slope a couple hundred yards behind the leading edge). The two things that can hold a slide back are friction with the terrain (this includes the trees getting pushed over) and viscous shearing within the distorting mass.

---

<div class="post-metadata">

**Author:** ![lieu](https://avatars.discourse-cdn.com/v4/letter/l/c2a13f/32.png) [@lieu](https://boards.straightdope.com/u/lieu)\
**Post date:** [April 22, 2015, 12:02pm UTC](https://boards.straightdope.com/t/what-are-the-mechanics-behind-this-landslide/718276/3 "2015-04-22T12:02:11Z")

</div>

Another site with that link has this…

_Zarechny, RU — Melting snow and heavy rains combined to cause a slow-moving landslide outside this town southeast of Moscow, Russia. Power lines, transmission towers, shrubs and trees — all pushed over and carried toward the road, which was soon buried deep under the debris._

There doesn’t appear to be much of a slope behind it, at least until you get some distance away. This would account for the slow speed of the mass.

ETA: …as Machine Elf mentions.

---

<div class="post-metadata">

**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\
**Post date:** [April 22, 2015, 12:15pm UTC](https://boards.straightdope.com/t/what-are-the-mechanics-behind-this-landslide/718276/4 "2015-04-22T12:15:09Z")

</div>

There are even [slower slides](http://www.timesunion.com/local/article/Slow-motion-landslide-takes-Adirondack-dreams-1409308.php) that take weeks or months to move a few 100 feet.