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Q: temperature below ground - is it cooler than above ground? ( Answered,   8 Comments )
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 Subject: temperature below ground - is it cooler than above ground? Category: Science > Earth Sciences Asked by: nassim99-ga List Price: \$2.00 Posted: 18 Jul 2006 12:22 PDT Expires: 17 Aug 2006 12:22 PDT Question ID: 747431
 ```what is the temperature underground? i am trying to prove that on average it is cooler below the ground than above...except for obvious exceptions where the temperature outside is cold enough to snow. this topic came up at dinner last night when i asked why it was that i cannot get cool water from my faucets at home. my friend replied, "because it is warm underground so the water gets warm." we live in san diego where the temperature on average is from 65-75 during the day and 50-60 at night.``` Request for Question Clarification by cynthia-ga on 18 Jul 2006 17:56 PDT ```This page might hold your answer: http://www.energyquest.ca.gov/story/chapter11.html```
 Subject: Re: temperature below ground - is it cooler than above ground? Answered By: hedgie-ga on 20 Jul 2006 05:23 PDT
 ```Well, if you dig deep enough, Cynthias answer would hold. But in a reasonable depth (5 to 100m) temperature is close to the average through the year, due to the 'thermal inertia' of the large mass. http://en.wikipedia.org/wiki/Thermal_inertia which means: in winter subsurface is warmer, in summer surface is warmer. More technical details are here: http://esrc.stfx.ca/borehole/node6.html```
 Subject: Re: temperature below ground - is it cooler than above ground? From: thither-ga on 18 Jul 2006 13:01 PDT
 ```"Ground temperatures At depths below four feet, ground temperature stays a constant 50 to 55 degrees Fahrenheit year-round." http://www.alliantenergygeothermal.com/stellent2/groups/public/documents/pub/geo_how_001211.hcsp I hope this helps a little. Have a good day.```
 Subject: Re: temperature below ground - is it cooler than above ground? From: nelson-ga on 18 Jul 2006 16:26 PDT
 ```In NYC, the subway stations are usually hotter than outside, but in the current heat wave, it's actually cooler down there.```
 Subject: Re: temperature below ground - is it cooler than above ground? From: ponder852-ga on 18 Jul 2006 17:10 PDT
 ```The main point about temparatures below ground is that they are relatively stable or constant compared to the daily and seasonal variations of above ground temperatures because of the insulating effect of the ground itself. (Very slow to warm up and very slow to cool down.) The deeper you go, the further from the surface, the more constant the temperature compared to the surface air variation. Air heats up and cools down quickly compared to bodies of water and soil and rock heats and cools slowest of the 3. At greater depths however temperatures, while stable, gradually increase and at the great depths some of our deep mines and drill holes are reaching the temperatures considerably above 50-55 as we get closer to the molten inner core of the planet. The insulating effect of the ground contributes to making the air in working mines very hot because the heat generated in the mining activities does not dissipate very fast from the mine air into the surrounding rock and so ventilation is required to remove the hot air as well as maintaining oxygen levels. Apparently 50-55 Fahrenheit at about 4 feet is considered average, however over sufficient time periods (years) the temperature can settle at lower (or higher) temperatures. "Permafrost" which apparently covers about 20% of the earths surface is soil at or below freezing and over sufficient time periods can extend to hundreds of metres below the surface. See: http://en.wikipedia.org/wiki/Permafrost or: http://www.alyeska-pipe.com/Pipelinefacts/Permafrost.html Animals, in both hot and cold climates, often burrow to reach the stable cooler or warmer areas respectively, compared to above ground air temperatures. It is better, for example, to live at a constant 50-55 below ground in a desert than to live exposed on the surface and suffer temeratures that may vary from below 0 to over 120 in the course of every 24 hours. Below ground cellars may seen cool however the main feature of cellars is the ability to maintain a constant temperature with a minimum of effort. Coober Pedy in South Australia (See: http://www.opalcapitaloftheworld.com.au ) is a modern example of a town built below ground to beat temperature variation as humans have done since before recorded history.```
 Subject: Re: temperature below ground - is it cooler than above ground? From: pinkfreud-ga on 18 Jul 2006 17:14 PDT
 ```When I was young, I went on a few spelunking trips in the summertime. One of the most notable thing about caves is the pleasant coolness. Even on a sweltering hot day, you'll feel cool (sometimes chilly) once you get underground.```
 Subject: Re: temperature below ground - is it cooler than above ground? From: ponder852-ga on 18 Jul 2006 17:25 PDT
 ```I nearly forgot the water temperature in the pipes. Whatever the temperature of the water at it's starting point (river, water tank, dam or reservoir) the longer it is in the pipes under the ground the closer the temperature will become to the temperature of the surrounding soil. If the soil temperature is 50-55 and the water temperature at it's source starts below 50-55 it will tend to absorb heat from the surrounding soil and increase towards 50-55. If it starts above 50-55 it will loose heat and tend to decrease towards 50-55.```
 Subject: Re: temperature below ground - is it cooler than above ground? From: cynthia-ga on 18 Jul 2006 17:51 PDT
 ```I understand why nassim99 is asking. I lived in Seattle most of my life where you turn on the tap and wait for the hot water to get hot. Cold is already cold. Then, I mo=ved to Las Vegas and lived there for 6 years, --what a difference! In LV, the hot is always ready to go, but when you turn on the cold tap, you have to wait for it to turn from hot to cold.```
 Subject: Re: temperature below ground - is it cooler than above ground? From: kottekoe-ga on 18 Jul 2006 20:15 PDT
 ```Well below ground the temperature is approximately the average of the surface temperature, so it is cooler than the hot days of summer and warmer than the coldest periods of the winter. In artic regions it can be below freezing, hence permafrost. In tropical regions it can be well above the 50-55 F degrees mentioned in the first comment. Of course, it is very hot at the center of the earth, so there is a constant flow of heat to the surface. This creates a thermal gradient that depends on the thermal conductivity of the bedrock (how good an insulator it is). A typical value would be about 30 degrees Centigrade per kilometer, so if you are less the 10 meters below the surface, the contribution from this would be only a fraction of a degree. If you several kilometers down at the bottom of a deep mine, it would be very hot!```
 Subject: Re: temperature below ground - is it cooler than above ground? From: jack_of_few_trades-ga on 19 Jul 2006 06:51 PDT
 ```Nassim, The pipes are likely within a couple feet of the surface of the ground. This means they are still somewhat affected by the outside temperature. Even if they are deeper, the temperature will be about 55 degrees. This is not at all cool compared to the ice cold 32 degree water you are used to drinking... that is why it does not seem cool.```