The Naked Scientists

The Naked Scientists Forum

Author Topic: Is there a crater in Devon at 50.61N, 3.79W?  (Read 3794 times)

Offline Lmnre

  • Sr. Member
  • ****
  • Posts: 178
    • View Profile
Is there a crater in Devon at 50.61N, 3.79W?
« on: 04/03/2012 14:04:19 »
A 12-mile crater at this location may have held water that collapsed the southeast rim. A good view is in Google maps at the 2mi/5km scale with the terrain on.


 

Offline OokieWonderslug

  • Full Member
  • ***
  • Posts: 93
    • View Profile
Re: Is there a crater in Devon at 50.61N, 3.79W?
« Reply #1 on: 04/03/2012 16:23:26 »
Doesn't look like it at all. Sorry.
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Re: Is there a crater in Devon at 50.61N, 3.79W?
« Reply #2 on: 05/03/2012 11:12:36 »
I must admit I cannot see anything that looks at all craterish - quite the opposite.  Maybe do a screen dump and use a simple draw programme to mark the edges?
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Re: Is there a crater in Devon at 50.61N, 3.79W?
« Reply #3 on: 05/03/2012 12:52:17 »
I'm not seeing it either.

I found that ArcGIS provides online topo maps:
http://www.arcgis.com/home/item.html?id=f2498e3d0ff642bfb4b155828351ef0e


It appears as if there is a ridge along A382, and perhaps a bit more hilly around Dartmoor National park than in the park.  However,  there are numerous hills within the park, and you can get some estimate of the topography by looking at the numerous streams in within the park.  Easdon Tor, 439 meters is not far from your coordinates.

Anyway, I agree with OokieWonderslug and imatfaal, not a crater.
Perhaps what you are seeing on Google Maps is a "Natural Area" which receives less irrigation than surrounding areas.

« Last Edit: 05/03/2012 12:55:36 by CliffordK »
 

Offline damocles

  • Hero Member
  • *****
  • Posts: 756
  • Thanked: 1 times
    • View Profile
Re: Is there a crater in Devon at 50.61N, 3.79W?
« Reply #4 on: 05/03/2012 18:51:29 »
If you look at the area in google maps, satellite view, at the exact scale suggested, there is an optical illusion of a circular feature roughly 12 mi diameter. It is mostly made up of small ridges, although part of the Southern section is actually gullies. The illusion is enhanced by vegetation.

The circle passes 1 mi North of Moretonhampstead in the North, right through Bovey Tracey in the East, about half mi North of Ashburton in the South, and through a featureless area that does include the label for Dartmoor National Park in the West.

Lmnre am I seeing the right feature?

I am "seeing it". I am not believing it is a crater. CK unfortunately the scale of your topo map is too large, so that most of the 'rim' falls just off the edge of it.
 

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 6564
  • Thanked: 7 times
  • Moderator
    • View Profile
Re: Is there a crater in Devon at 50.61N, 3.79W?
« Reply #5 on: 06/03/2012 03:53:20 »
Actually, you have uncovered my family Country House. Exactly located at 50" 36'47.33 N   3"47' 57.78 W

The ridges as well as the !_!-shaped lake are very good evidence of the glaciation that made the landforms of this part of England (er, Cornwall?)

 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Re: Is there a crater in Devon at 50.61N, 3.79W?
« Reply #6 on: 06/03/2012 07:41:10 »
Actually, you have uncovered my family Country House.

I never realized you were one of the Baskervilles. Of course, that's not the sort of thing one wants to say too much about in Texas, so I can understand why you never mentioned it before now.
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Re: Is there a crater in Devon at 50.61N, 3.79W?
« Reply #7 on: 06/03/2012 09:50:39 »
Actually, you have uncovered my family Country House. Exactly located at 50" 36'47.33 N   3"47' 57.78 W

The ridges as well as the !_!-shaped lake are very good evidence of the glaciation that made the landforms of this part of England (er, Cornwall?)

And what is really spooky is that I have actually been to your ancestral country home!  It's a place called Heatree House ( course you know this as lord of the manor) - and the little round structure is a recreation of a bronze age roundhouse which I popped into see when visiting a friend on a dig nearby.  It's a lovely spot - but my personal preference would be to get rid of all the teenage kids who tend to treat the place as if it is an activity centre
 

Offline Lmnre

  • Sr. Member
  • ****
  • Posts: 178
    • View Profile
Re: Is there a crater in Devon at 50.61N, 3.79W?
« Reply #8 on: 06/03/2012 20:15:50 »
To begin with, I now see that there's nothing there.

Two mistakes on my part. First, the word "crater" was poorly chosen, and I should have used the word "rim" to better describe what I thought I saw because there isn't any obvious depressed "bowl" within the rim. I was thinking it might be some sort of eroded upheaval cone, and if it held water, there would be islands here and there. Second, the altitude of the perceived "rim" is 200 meters along the north, east and south sectors, but 300 to 400 meters along the west sector. I tediously sketched it out, and I can now see the illusion of a rim that doesn't exist.

Okay, I will sit on my hands for a while and keep quiet.
 

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 6564
  • Thanked: 7 times
  • Moderator
    • View Profile
Re: Is there a crater in Devon at 50.61N, 3.79W?
« Reply #9 on: 07/03/2012 01:31:32 »
Why? It _IS _ a dome - a granitic dome - see Wikipedia "geology map (sic)" of the U.K.

http://en.wikipedia.org/wiki/File:Geology_Map_UK.svg
 

Offline Lmnre

  • Sr. Member
  • ****
  • Posts: 178
    • View Profile
Re: Is there a crater in Devon at 50.61N, 3.79W?
« Reply #10 on: 07/03/2012 18:33:19 »
A granitic dome, thanks. Would the dome also cause those geologic features called "tors" that I see there?
 

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 6564
  • Thanked: 7 times
  • Moderator
    • View Profile
Re: Is there a crater in Devon at 50.61N, 3.79W?
« Reply #11 on: 08/03/2012 02:56:32 »
If they are phalic - yes
 

Offline Mazurka

  • Hero Member
  • *****
  • Posts: 510
    • View Profile
Re: Is there a crater in Devon at 50.61N, 3.79W?
« Reply #12 on: 09/03/2012 15:02:16 »
Sorry old chap but from my recollection of the shape of tors I think you need to go and see a doctor [:0]

Technically, the tors are geomorphological features because they are thought to have formed as a result of weathering exploiting lines of weakness where the granite is exposed at the surface. 

In the case of  Dartmoor / Bodmin Moor
As the granite cooled following intrustion, it contracted and cracked leaving vertical joints.
As the granite was uplifted as the rock above it was eroded away the decrease in pressure is thought  to have lead to horizontal jointing.
Water circualting through the rock (heated by residual and radiogenic heat) weathered some of the feldspar minerals (turning them to clay) particuarlly along lines of weakness (joint sets) thus exagerating them and making physical weathering easier
Finally sat at the surface weathering could properly occur - initial tropical weathering (the UK used to be in the tropics (when JB was a lad ;))  and then glacial / freeze thaw weathering finished sculpting the outcrops we see today.

Although they are most common in granite type rocks, they sometimes occur in other rocks such as quartzite or gritstone by physical weathering.
 

The Naked Scientists Forum

Re: Is there a crater in Devon at 50.61N, 3.79W?
« Reply #12 on: 09/03/2012 15:02:16 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums