<p>Permafrost is defined as</p>

<blockquote>
  <p>a ground, or medium, (including rocks, soils and organic matter) with a mean annual temperature less than 0 °C for at least 2 consecutive years.</p>
</blockquote>

<p>The smooth appearance of the walls can be explained by understanding how permafrost works. Permafrost is characterized by an active layer, which is a layer normally at the surface which freeze yearly during winter and thaw during summer - this layer at Yamal can be 1-2 m deep depending on the local ground characteristics (snow depth, albedo, slope, air temperature, thermal conductivity, runoff etc).  The ground in the area is ice-rich.</p>

<p>Then let's assume this crater was caused by a methane bubble escaping/exploding and walls could be rough immediately following the event. By deduction, there should not be an active layer found on the walls following the explosion, as it is the first time this ground (walls) were exposed to air. During the middle of the summer, above 0°C air enters the hole due to convection. The ground is ice-rich (can be porous or invisible ice but still ice-rich) and active-layer start to form on the wall. </p>

<p>Due to the near vertical orientation of the walls, saturated soil (or active layer in formation) cannot stand because as soon as it thaw to a depth exceeding its equilibrium limit, it fall at the bottom of the crater due to gravitational forces, exposing a new frozen surface (and the cycle continue until equilibrium can take a few years). Thawing sediments in ice-rich soils can reach saturation quickly, further adding to the weight and accelerating the time of the fall. Rugged and unequal surface are typically the first elements to thaw and fall.</p>

<p>I took this picture about an hundred km from the featured crater.
<img src="https://i.sstatic.net/XZovW.jpg" alt="enter image description here"></p>

<p>This display a very ice-rich section of the Yamal Peninsula littoral in the course of erosion. This coastal section has been eroding for decades at least. At the top the active layer is light brown, and look dry (1 m deep). Just under this top-layer, the ice is poly-genetic: ice wedge ice-rich soil and massive ice can be seen as well. The active layer cannot stand on the side for the reasons I exposed in the previous paragraph (gravity).</p>

<p>Side-note, the jagged edges were not initiated by anything related to a pingo. It takes decades, up to many centuries for a pingo to develop until its natural collapse. When it happen, a depression can form at its center - which could lead to a lake, but these are not overnight processes. Also, contours of the pingo mound would not appear as jagged edges if this was a pingo - the remains would appear pretty old and vegetated, alike the surrounding countryside.</p>

CC BY-SA 3.0
2016-12-26T14:07:52.623Z
Typo: "enter the whole" -> "enters the hole"
Spencer
CC BY-SA 3.0
2016-12-26T14:18:58.840Z
@Spencer thanks for noticing, I just updated.
marsisalie
CC BY-SA 4.0
2020-09-07T22:43:18.120Z
"above 0°C air enters the hole due to convection." Wouldn't the cold air pool at the bottom --> no convection?
Keith McClary
CC BY-SA 4.0
2020-09-09T11:33:43.333Z
@KeithMcClary this is what it would mean I guess. But not sure what this imply in the present context.
marsisalie
CC BY-SA 3.0
2015-01-17T13:48:08.530Z
2016-12-26T14:18:27.867Z
2016-12-26T14:18:27.867Z
marsisalie
<p>A friend of mine works at the Permafrost institute in Moscow and he and his colleagues generally support this idea. I think that edges were formed by falling pieces of soil and vertical walls were formed when big methane bubble that went off the deeper layers.  </p>

CC BY-SA 3.0
2014-08-13T20:13:19.400Z
Did they have anything published about it?
gerrit
CC BY-SA 3.0
2014-08-12T13:48:11.723Z
2014-12-11T07:56:08.233Z
2014-12-11T07:56:08.233Z
Dmitry
<p>Wackiest answer:</p>

<p>It has all the hallmarks of a plasma discharge. Burn marks around the rim next to the saw tooth serrations resemble EDM machining scars.</p>

<p><a href="https://i.sstatic.net/bLJFH.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/bLJFH.jpg" alt="EDM machining scars"></a></p>

<p><a href="https://i.sstatic.net/bKIES.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/bKIES.jpg" alt="crater walls show characteristic scalloping of electrical discharge"></a></p>

<p><a href="https://i.sstatic.net/rn8Ky.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/rn8Ky.jpg" alt="vertical walls cut by plasma, saw tooth edge results from hypersonic blast"></a></p>

<p><a href="https://i.sstatic.net/sWtLJ.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/sWtLJ.jpg" alt="large crater in Mexico showing same triangular shapes around rim"></a></p>

<p><a href="https://i.sstatic.net/4RwIs.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/4RwIs.jpg" alt="diagram of electrical discharge event, shock wave blast creates triangular shaped wave which superimposes on the surface"></a></p>

<p>There are some excellent videos on youtube about electric geology if you are interested in more detailed info.</p>

<p><a href="https://www.youtube.com/watch?v=ITtvK1wyptU&amp;index=30&amp;list=PLwOAYhBuU3UeYFyfm2LilZldjJd48t6IY" rel="nofollow noreferrer">Video about electric geology, explains arc blasted earth features</a></p>

<p>Speculation on the cause could go wild. Some natural phenomena might account for such an event, but likely would have been easily noticed by locals, even at a great distance.</p>

<p>There has been much chatter lately about hypersonic reentry vehicles as weapons.</p>

<p><a href="http://www.nationaldefensemagazine.org/archive/2015/August/Pages/HypersonicWeaponsRaceGathersSpeed.aspx" rel="nofollow noreferrer">http://www.nationaldefensemagazine.org/archive/2015/August/Pages/HypersonicWeaponsRaceGathersSpeed.aspx</a></p>

<p><a href="http://rbth.com/defence/2016/09/27/russia-could-get-hypersonic-weapons-by-early-2020s_633689" rel="nofollow noreferrer">http://rbth.com/defence/2016/09/27/russia-could-get-hypersonic-weapons-by-early-2020s_633689</a></p>

<p>Such a device creates very different conditions in the atmosphere around it as it forms a plasma from the high speeds involved. It is likely that such weapons are being tested, far from man, but somewhere accessible. A hole that size would only require a test sized vehicle, a scale model maybe. And with such obvious success, you might want to leak pics to notify the enemy of your capability, because the best defense is a good offence.</p>

<p>/kook</p>

CC BY-SA 3.0
2016-12-26T05:13:59.500Z
Could you perhaps add some references?
L.B.
CC BY-SA 3.0
2016-12-26T04:38:53.553Z
2016-12-26T18:03:29.027Z
2016-12-26T18:03:29.027Z
daric
<p>I expect most of you have heard of <a href="http://www.iflscience.com/environment/scientists-think-they-may-have-solved-siberian-crater-mystery" rel="noreferrer">this</a> by now.</p>

<p><img src="https://i.sstatic.net/QZOTx.jpg" alt="enter image description here"></p>

<p>All the news is about whether or not they were formed by the release of methane, but it is also mysterious to me why this crater has jagged edges but smooth vertical walls. It almost looks like it has been drilled.</p>

<p>I'm not a geologist but I would expect it to be rough all the way down. Can someone explain why it isn't?</p>

CC BY-SA 3.0
2015-01-14T20:50:59.653Z
Thanks, [this picture](http://i.dailymail.co.uk/i/pix/2014/11/12/1415786374689_wps_8_Yamal_crater_7_must_credi.jpg) is particularly striking.
spraff
<geology><methane><permafrost>
Why do the Siberian methane craters have smooth vertical walls?
spraff
# Why do the Siberian methane craters have smooth vertical walls?

(Asked by: username_0 on 2014-08-10)

I expect most of you have heard of [this](http://www.iflscience.com/environment/scientists-think-they-may-have-solved-siberian-crater-mystery) by now.

![enter image description here](https://i.sstatic.net/QZOTx.jpg)

All the news is about whether or not they were formed by the release of methane, but it is also mysterious to me why this crater has jagged edges but smooth vertical walls. It almost looks like it has been drilled.

I'm not a geologist but I would expect it to be rough all the way down. Can someone explain why it isn't?

**Tags:** geology, methane, permafrost

> **Comments:**
> **username_0**: Thanks, [this picture](http://i.dailymail.co.uk/i/pix/2014/11/12/1415786374689_wps_8_Yamal_crater_7_must_credi.jpg) is particularly striking.  

---

## 3 answers

### Answer by username_1 on 2015-01-17. Score: 19

Permafrost is defined as

> a ground, or medium, (including rocks, soils and organic matter) with a mean annual temperature less than 0 °C for at least 2 consecutive years.

The smooth appearance of the walls can be explained by understanding how permafrost works. Permafrost is characterized by an active layer, which is a layer normally at the surface which freeze yearly during winter and thaw during summer - this layer at Yamal can be 1-2 m deep depending on the local ground characteristics (snow depth, albedo, slope, air temperature, thermal conductivity, runoff etc). The ground in the area is ice-rich.

Then let's assume this crater was caused by a methane bubble escaping/exploding and walls could be rough immediately following the event. By deduction, there should not be an active layer found on the walls following the explosion, as it is the first time this ground (walls) were exposed to air. During the middle of the summer, above 0°C air enters the hole due to convection. The ground is ice-rich (can be porous or invisible ice but still ice-rich) and active-layer start to form on the wall.

Due to the near vertical orientation of the walls, saturated soil (or active layer in formation) cannot stand because as soon as it thaw to a depth exceeding its equilibrium limit, it fall at the bottom of the crater due to gravitational forces, exposing a new frozen surface (and the cycle continue until equilibrium can take a few years). Thawing sediments in ice-rich soils can reach saturation quickly, further adding to the weight and accelerating the time of the fall. Rugged and unequal surface are typically the first elements to thaw and fall.

I took this picture about an hundred km from the featured crater.
![enter image description here](https://i.sstatic.net/XZovW.jpg)

This display a very ice-rich section of the Yamal Peninsula littoral in the course of erosion. This coastal section has been eroding for decades at least. At the top the active layer is light brown, and look dry (1 m deep). Just under this top-layer, the ice is poly-genetic: ice wedge ice-rich soil and massive ice can be seen as well. The active layer cannot stand on the side for the reasons I exposed in the previous paragraph (gravity).

Side-note, the jagged edges were not initiated by anything related to a pingo. It takes decades, up to many centuries for a pingo to develop until its natural collapse. When it happen, a depression can form at its center - which could lead to a lake, but these are not overnight processes. Also, contours of the pingo mound would not appear as jagged edges if this was a pingo - the remains would appear pretty old and vegetated, alike the surrounding countryside.

> **Comments:**
> **username_2**: Typo: "enter the whole" -> "enters the hole"  
> **username_1**: @username_2 thanks for noticing, I just updated.  
> **username_3**: "above 0°C air enters the hole due to convection." Wouldn't the cold air pool at the bottom --> no convection?  
> **username_1**: @username_3 this is what it would mean I guess. But not sure what this imply in the present context.  

---

### Answer by username_4 on 2014-08-12. Score: 4

A friend of mine works at the Permafrost institute in Moscow and he and his colleagues generally support this idea. I think that edges were formed by falling pieces of soil and vertical walls were formed when big methane bubble that went off the deeper layers.

> **Comments:**
> **username_5**: Did they have anything published about it?  

---

### Answer by username_6 on 2016-12-26. Score: -2

Wackiest answer:

It has all the hallmarks of a plasma discharge. Burn marks around the rim next to the saw tooth serrations resemble EDM machining scars.

[![EDM machining scars](https://i.sstatic.net/bLJFH.jpg)](https://i.sstatic.net/bLJFH.jpg)

[![crater walls show characteristic scalloping of electrical discharge](https://i.sstatic.net/bKIES.jpg)](https://i.sstatic.net/bKIES.jpg)

[![vertical walls cut by plasma, saw tooth edge results from hypersonic blast](https://i.sstatic.net/rn8Ky.jpg)](https://i.sstatic.net/rn8Ky.jpg)

[![large crater in Mexico showing same triangular shapes around rim](https://i.sstatic.net/sWtLJ.jpg)](https://i.sstatic.net/sWtLJ.jpg)

[![diagram of electrical discharge event, shock wave blast creates triangular shaped wave which superimposes on the surface](https://i.sstatic.net/4RwIs.jpg)](https://i.sstatic.net/4RwIs.jpg)

There are some excellent videos on youtube about electric geology if you are interested in more detailed info.

[Video about electric geology, explains arc blasted earth features](https://www.youtube.com/watch?v=ITtvK1wyptU&index=30&list=PLwOAYhBuU3UeYFyfm2LilZldjJd48t6IY)

Speculation on the cause could go wild. Some natural phenomena might account for such an event, but likely would have been easily noticed by locals, even at a great distance.

There has been much chatter lately about hypersonic reentry vehicles as weapons.

<http://www.nationaldefensemagazine.org/archive/2015/August/Pages/HypersonicWeaponsRaceGathersSpeed.aspx>

<http://rbth.com/defence/2016/09/27/russia-could-get-hypersonic-weapons-by-early-2020s_633689>

Such a device creates very different conditions in the atmosphere around it as it forms a plasma from the high speeds involved. It is likely that such weapons are being tested, far from man, but somewhere accessible. A hole that size would only require a test sized vehicle, a scale model maybe. And with such obvious success, you might want to leak pics to notify the enemy of your capability, because the best defense is a good offence.

/kook

> **Comments:**
> **username_7**: Could you perhaps add some references?  

---

