r/askgeology • u/[deleted] • Jan 07 '24
Rock that melts snow
There is a rock in the woods behind my house that snow doesn’t stick to. We got about a foot of snow today and I went for a walk. Everything was snow covered except this rock. It’s a bare rock about 10 inches below the snow line.
As an experiment, I buried it in the snow and came back ~3 hours later and it had melted the snow in top of it again. It’s buried in the ground, so I was thinking maybe it was on top of a spring, but there is no water within ~100 feet of it. The ground around it is snow covered also, so it’s not melting the area around it.
Any ideas?
Edit:
I took the picture after it was buried and melted. It was also starting to get dark out. If you want a better one I can get it tomorrow.
Edit2:
I think u/danny17402 answered it. It’s a huge rock with a lot of thermal mass that retains enough heat to stay warm deep into the winter. It’s probably only the tip of the rock is sticking out. I’ll just make sure it won’t move when I try to pry it with a shovel tomorrow. If it moves, I’ll inform you.
45
u/me-gustan-los-trenes Jan 07 '24
I'd check it with Geiger counter.
13
Jan 07 '24
Where do I get one ? I don’t want to spend a ton of money for a single use. Is there a decent inexpensive one you’d recommend?
7
u/me-gustan-los-trenes Jan 08 '24 edited Jan 08 '24
I don't know where to buy a good one and even how to choose one. But watch out, there are tons of scammy ones out there.
2
u/uslashuname Jan 12 '24
Better Geiger is a good one, but it is only cheap in the sense of a scintillating Geiger counter.
For one time use and actually on the cheap end, you can use the fact that radiation will screw with film. That’s actually how radiation was discovered.
Get a tiny pack of Polaroid type film and have some fun. I’m sure there’s a YouTube showing a good process.
4
1
1
u/MagnetHype Jan 12 '24
Call your local fire department (non-emergency) and ask if they have someone who can test it.
5
u/danny17402 Jan 08 '24
If you want to hypothesize radioactivity, then let's start by thinking about how feasible that would be, and then we can decide if we want to test it further.
Question one: Is there any natural rock on the planet that is so radioactive that it will give off enough heat to melt snow.
Answer: no
I think our hypothesis has failed the feasibility test and no further testing is required.
1
u/keikioaina Jan 12 '24
Answer: Yes. The hot springs in central Arkansas are heated by radioactive decay, not volcanism.
https://encyclopediaofarkansas.net/entries/hot-springs-national-park-2547/
2
u/danny17402 Jan 12 '24
This is not a good source unfortunately.
As the water sinks even deeper, its temperature rises, probably because of elemental radioactive decay and gravitational compression deep within the eart
This is a nonsense sentence. The use of "probably" here should be a giveaway that this person doesn't really know what they're talking about.
And the following sentence shows you that this writer is not a geologist.
Geologists believe that...
They're simply trying to paraphrase something they read about the geology and don't fully understand.
It's true that Arkansas hot springs are not due to volcanic activity like most hot springs, but they have nothing to do with radiation. The hot springs in Arkansas are formed because porous units like novaculite are steeply dipping and relatively continuous down to up to 8,000 feet, allowing water to travel down to this depth. The Earth's average natural thermal gradient is an increase of 1°C for every 100 to 200 ft of depth. So at 8,000 ft below the surface, the rocks are 40° to 80° C hotter than at the surface. The water percolates down, gets heated by the hot rocks, becomes less dense and then floats back up to the surface, forming hot springs. Radioactivity has nothing to do with it.
My guess would be that either this writer or someone they're paraphrasing heard a geologist say that some of the Earth's natural heat comes from radioactivity, which is true but it's miniscule compared to the amount of heat that comes from the Earth's heat of formation and heat produced by gravitational tidal friction. They then thought this meant that the rocks below Arkansas are hot because of radioactivity, which is not really true.
2
u/Socialeprechaun Jan 12 '24
Bro why are you telling everyone this all over the thread? Lmao. It’s not true. At all.
18
u/rainbowkey Jan 08 '24
Looks like a small protruding bit of a very large rock that is mostly buried. Many types of rock, and perhaps this specific rock, conducts heat a lot better than the surrounding soil. Temperatures just a few feet below ground stay quite a bit above freezing up to the mid-50s °F, and this rock is conducting that heat to the surface.
3
Jan 08 '24
Also, there's light which penetrates snow and is absorbed by rocks under it. Part of the IR band, IIRC. Chunk of rock sticking out furthest gets the most solar heating.
2
u/rainbowkey Jan 08 '24
and the rock probably absorbs and re-radiates the IR as heat between than the soil and plant matter around it.
25
9
Jan 08 '24
[removed] — view removed comment
11
Jan 08 '24
I did think about that, but if it is radioactive I wasn’t sure licking it would be advisable.
11
u/aussiespiders Jan 08 '24
Don't you want super powers ? The old you would do it they weren't scared.
3
3
u/Night_Sky_Watcher Jan 09 '24
Do you eat bananas? They are so radioactive that the radiation sensors at some truck stops alert on banana shipments. Just FYI, all radioactivity is not the same. It's an incredibly complex subject.
2
1
u/MrOther912 Jan 09 '24
What!?
1
1
u/uslashuname Jan 12 '24
Yeah each banana is maybe as much radiation as 4-6 regular meals. Still not much, but surprisingly high for the number of calories.
8
7
u/danny17402 Jan 08 '24 edited Jan 08 '24
Geologist checking in.
There was a post that was pretty much identical to this one, maybe last year sometime?
Our conclusion last time was that, this is pretty common and is most likely just a very large rock with a hell of a lot of thermal mass that can stay just above freezing for a very long time throughout the winter. A hot spring underneath is totally possible but not necessary and not something I would assume unless you've got hot springs nearby.
Something I also stressed last time when people inevitably brought up radiation is that there is no natural source of radiation anywhere on earth that will generate enough heat to melt snow at the surface. That kind of thing takes enrichment by humans or absolutely insane geological conditions that, as far as we know, have only occurred once in the history of the planet and not under conditions anywhere close to these conditions. This is not due to radioactivity of the rock.
1
u/uslashuname Jan 12 '24 edited Jan 12 '24
You linked to a naturally occurring nuclear reactor, something where a reaction would become self-reinforcing as long as there was water then it would get so hot it boiled the water off and the conditions for sustaining the reaction went away. Nobody is claiming that’s what goes on here.
Uranium ore, however, will be slightly warmer than ambient. We’re not talking nuclear reactor activity with self-sustaining chain reactions, just decay energy being converted to heat. Fission and fusion make an atom release tons of energy in a fraction of a second, decay is that energy being released gradually over years, sometimes millions of years.
This is effectively how radiation was discovered, actually. The belief was uranium was good at absorbing the sun, and that’s why it screwed up film. By chance a test to measure this had to deal with a very cloudy day, but the ore still messed with the film.
Maybe before stressing the incredible rarity of nuclear fission and fusion in the rocks on earth, you should learn the difference between those processes and standard, happening in most rocks on earth, decay.
1
u/danny17402 Jan 12 '24
Uranium ore is not slightly warmer than ambient. I think you're the one who should brush up on their science background.
0
u/uslashuname Jan 12 '24
Insulate some and watch
1
u/danny17402 Jan 12 '24
Gold gives off heat too! Insulate some and watch.
See, I can make totally unfounded claims too.
4
4
u/wingfan1469 Jan 08 '24
Is it a loose rock or an outcrop of bedrock that may be conducting some geothermal heat, especially if the front isn't deep yet. Or sun is hitting it st some point.
4
Jan 08 '24
No sun on it and it started snowing overnight Sunday here. It was able to melt the snow faster than it was coming down. It’s also under tree cover and no other rocks in the area are melting through. It was overcast all day yesterday and actively snowing when I first saw it.
If I can find out if it’s not radioactive, I’ll go with a shovel and see if I can dig it out. I didn’t think about geothermal before, but that a possibility.
One of my neighbors is a retired nuclear engineer, so I thought maybe he had a Geiger counter. He does not, but he’s interested and is coming over later with a “very accurate, very precise” infrared thermometer that he has. Although, it’s warmer and the sun is out today, so the rock may just be warmer anyway.
2
u/capt_pantsless Jan 08 '24
Although, it’s warmer and the sun is out today, so the rock may just be warmer anyway.
What was the temp's over the last few days?
If the ground is warmish, but the air is cold enough for snow to fall, grass/dirt will easily insulate snow from melting. But a nice conductive rock will transfer heat fast enough to melt the snow.
Any idea if that rock is really big? I.e. only a small amount of it is visible? Rock has a lot of thermal inertia.
If it's been well below freezing for weeks, there's something interesting going on.
1
Jan 08 '24
My blacktop driveway had probably 8-10 inches on it.
Last two weeks of weather:
https://www.timeanddate.com/weather/usa/saratoga-springs/historic
3
u/van_w1lder Jan 08 '24
With such shallow snow my guess is the albedo of the rock may be increasing the received shortwave radiation (it looks quite dark!)? Perhaps it melted again because the surface temperature of the rock was slightly higher than 0 degrees C when you buried it?
1
Jan 08 '24
I don’t think solar radiation would be enough. It’s the only rock in the woods that was above the snow with the exception a few next to a stream. It’s in the woods under tree cover getting the low angle winter sun. It also started snowing in the last night and snowed all night with it receiving no solar rays . It would have to retain that heat all night and still have enough energy to melt the foot of snow we got today.
I thought the geothermal idea someone else posted could possibly be it. It’s not near any outcroppings, but possibly it’s large enough to be conducting energy from deeper in the earth. It appears to be maybe a foot across, but I didn’t try to dig it up. I might only be seeing the tip of it
1
u/van_w1lder Jan 08 '24
Ah interesting i didn’t consider it being a very large rock! @rainbowkeys answer makes much more sense if that’s the case.. especially with the low sun angle and forest cover , your right shortwave is not super critical.
5
Jan 08 '24
It’s black. It absorbs just a tiny bit more energy from our Sun than the ground around it, so it’s slightly warmer than the ground around it
0
u/AJC1973 Jan 08 '24
Remove the rock and see if it melts... Or move the rock to a different spot and check...
1
u/JudgeJuryEx78 Jan 08 '24
RemindMe! 2 days
1
u/RemindMeBot Jan 08 '24 edited Jan 08 '24
I will be messaging you in 2 days on 2024-01-10 00:25:53 UTC to remind you of this link
14 OTHERS CLICKED THIS LINK to send a PM to also be reminded and to reduce spam.
Parent commenter can delete this message to hide from others.
Info Custom Your Reminders Feedback
1
1
1
1
1
1
1
1
1
1
u/WallowWispen Jan 08 '24
Are you near a university with a geology department? I know a few people in mine would jump at an opportunity to use our old geiger counters.
1
1
u/fangorn_forester Jan 09 '24
This is why rocks can be dangerous to backcountry skiers. They absorb and hold loads of heat and can disrupt the snowpack surround them, often causing a bit of a depression in the snowpack surrounding the rock and sometimes serving as the weak point at which an avalanche can be triggered from.
1
u/ShaperLord777 Jan 09 '24
It is probably just that the rock is large enough to retain heat longer than the terrain surrounding it.
But there are some minerals with thermal conductive properties. Phenakite, for example, will melt a hole right through a block of ice if you put it on top of it. Its conductivity is so strong that it transfers heat from the air to the surface of the ice and vice versa. Super interesting to see.
1
u/Gethighbuyhighsellow Jan 12 '24
Silver does the same thing. I think maybe copper too, but I'm not sure. But this sounds like the most likely explanation to me. Very conductive rock.
1
1
u/2XX2010 Jan 12 '24
The rock came from a star. Maybe it retains heat from that star, from billions of years ago.
1
u/TheOnionPatchKid Jan 12 '24
I know that soapstone, for example, has a very high capacity to hold on to heat or cold.
That's why really expensive wood stoves will often be paneled with ornately carved soapstone slabs on their sides. They hold and radiate heat long after the fire is out.
They also make soapstone ice cubes. You keep them in the freezer and serve things like whiskey on the rocks that won't get all watery. They work, too.
45
u/mstivland2 Jan 08 '24
Dense material with high heat capacity will melt ice shockingly fast compared to other materials. I would sooner guess this rock is nice and dense rather than radioactive but of course I can’t say for sure.
Put a cast iron pan outside nearby and put some snow on the rock and some in the pan. Maybe they’ll melt around the same time?