# Tag Info

33

Quoting from John Russell's response to this article, "This is arrant nonsense!" Russell concludes with How did this paper get through the peer-review and editorial review processes? What technical standards were applied to determine the apparent merit of its contents so as to justify its inclusion in a reputable journal? Just because something is ...

32

Part 1, see Neos answer. Earth will lose its heat no matter what we do, and our extraction of geothermal energy is insignificant (Wikipedia quotes a BP figure of 11.4 GW electrical, 28 GW heating). To answer part 2 of your question: if the Earth's core loses its heat, this will not have a major direct impact on climate. Internal heat generation is ...

25

I'm a volcanologist and I have worked on erupting volcanoes. First of all, volcanologists almost never actually wear those suits. Heat is almost never the hazard that matters in the situations in which we work. The hazards are usually the chance of being hit by ballistics, or getting gassed. The reason you see those suits so often is that they look really ...

20

This question is relevant, Why is the inside of the Earth so hot? The short answer is the core is losing heat no matter what we do. You see, heat is transported from the core to the surface, but its important to think of heat in terms of energy. Since there is a finite amount of energy within the earth, we are actually transferring energy from the inside to ...

18

Put a frying pan on a stove burner and make the pan hot. Measure its temperature every minute over half an hour or so to get an idea of how rapidly it naturally cools. Then start the experiment over again. This time, take a needle and touch and hold its tip to the frying pan so that it acts as a heat sink. The relative sizes of frying pan and needle will ...

17

No, this seems highly unlikely. According to online sources: Average human power consumption in 2008 was estimated at 15 TW. Total annual heat loss from the Earth due to the surface heat flux is estimated at 44.2 TW. Estimates of the electricity generating potential of geothermal energy around the world are consistently less than 2 TW. So although the ...

16

This is probably an observational effect that is quite common in the Earth Sciences. In scientifically progressing societies there is a higher proportion of observations due to a number of effects: awareness of science (not interpreting it as a wonder) ability to record events ability to observe (think 12 hour day in the factory vs. free weekend) technology ...

16

The temperature does indeed increase with depth, something that is a problem in deep mines or deep drilling, but a benefit for geotermal heating. The heat originates mostly from radioactive decay, but there is also a fraction of primordial heat from the formation of the Earth. As a rule of thumb, geologists often assume 25°C/km temperature increasements ...

15

What neither the authors nor the response by John Russell takes into account is that all underground oil and gas is stored inside tiny pores of rocks. An oil reservoir is not a big underground cave, it is a very fine-grained sponge made of stone filled with oil. In essentially all cases, there is more stone than oil (by volume). This means that since oil is ...

13

Could all the drilling and digging to use the earth's natural heat as geothermal energy be affecting Earth's core, causing it to cool down? Yes. But by how much? Let's do some rough math. We'll just be concerned with orders of magnitude here. Suppose we have a uniform sphere the size of the Earth. Call it 1021 cubic meters. Suppose this sphere is made ...

13

... causing it to cool down? This answer to the question 'Why has Earth's core not become solid?' over on Physics seems to claim the answer is no. The core is heated by radioactive decays of Uranium-238, Uranium-235, Thorium-232, and Potassium-40, all of which have half-lives of greater than 700 million years (up to about 14 billion years for Thorium). ...

13

This is a very good question. There a few main heat sources: Heat(and work) left over from the formation of the earth, work (potential energy) generated by dense iron sinking into the center of the earth and forming a core, and radioactive energy. Since the Thermal diffusivity of the materials that make up the earth is low, heat transport is very slow and ...

13

Whether volcanic activity fluctuates depends rather on the timescales you are looking at. Crisp (1984) compiles available data on igneous activity lasting for longer than 300 years and concludes that over the past 180 million years the annual average magmatic output each year is around 30km3, of which ~75% is produced at mid-ocean ridges. The most obvious ...

13

The conventional explanation for the Earth's magnetic field is that some combination of differential rotation and/or convection occurs in the Earth's outer core, primarily in molten iron-nickel (+ sulphur, hydrogen etc.), which acts as a kind of dynamo. Whilst we can't prove it by direct observation, this seems an eminently plausible mechanism. If this is ...

11

I think the answer to "Why don't scientists use fire entry suits to study volcanoes?" is that this is a question of professional ethics rather than of technology. For some institution to support, condone, or fund such a proposal, it would first have to conduct some sort of a safety review. At a significant cost, this approach would encourage risky behavior, ...

11

It is still a little known fact that radiation play an important role in the Earth's mantle. Experiments show that mantle-material becomes transparent to infrared radiation at increasing pressures (http://www.esrf.eu/news/general-old/general-2004/earthbadro/index_html). I would also say that the mantle is currently not understood in a way where estimates of ...

11

There are currently two ways to extract geothermal energy: one mainstream, one still at the experimental / demonstration level. Pollack et al (2010) estimate the global geoethermal heat loss at 44 TW (by comparison, civilisation's rate of energy use is about 20 TW). As the USA Department of Energy notes, all methods rely on the combination of three factors: ...

10

To explain the earth science bit (how a heat exchanger works is beyond the scope of the site). The Earth is essentially cooling, losing heat from the interior by conduction to space. this heat flux can be used to heat, for example water at depth since temperature increases with (significant) depth in the earth's crust. It is not necessary to be near a plate ...

10

Yes, there is a correlation. In other words: places with hot springs are more likely to experience earthquakes than places without hot springs. The relationship is scale-dependent in time and space (your house might not sit on a hot spring but still get earthquakes). Ideally I'd dig around and find actual data to quantify this spatial correlation (and I ...

10

Assuming a thermodynamic equilibrium between heat from below and heat escaping into outer space, and assuming an energy from below of 44 to 47 terawatts (the Earth's current internal heat budget), that means the surface temperature would be about 35 or 36 kelvins by the Stefan-Boltzmann law: $$\varepsilon \sigma A T^4 = \phi$$ where $\varepsilon$ is the ...

8

In most cases, probably not. Oil could be considered a metamorphic mineral, formed by "gentle" heating. That is gently on a geological scale - still enough to burn your hands! Geothermal systems work most efficiently with a large temperature difference (Third Law of Thermodynamics). As soon as the temperatures increase enough to be interesting from a ...

8

This is a bit of a what-if kind of answer, with some rough estimates. Just considering the cooling aspect - let's pretend that Earth is solid for a momnet. The time-dependent heat equation tells us how long it will take for a change in temperature to travel a certain distance by conduction (the 'characteristic timescale'). The distance to the outer core, ...

8

Hot springs usually exist in volcanic regions or in areas where there are extensive (normal) faults. The water circulates through the fault zones (basically damaged zones with high permeability) bringing heat from great depths. However these faults don't have to be active. Therefore a correlation between location of hot springs and present day seismic ...

8

The heat equilibrium depth will vary for different locations due to: Differences in geothermal gradient at different locations (heat emitted by rock). It is generally accepted that the global geothermal gradient is between ${25 ^o C/km}$ & ${30 ^o C/km}$. At some locations the gradient can vary between ${15.4 ^o C/km}$ & ${102.6 ^o C/km}$. The ...

8

Your question has an incorrect assumption built in. Near surface ground water temperatures are not generally colder, but rather reflect the average annual temperature. This will be colder than surface temps in summer, but warmer in winter. There is an an additional effect if your rainfall isn't evenly distributed over the course of the year, as percolating ...

7

The previous answers contain important facts, but neglect recent discoveries. As tobias47n9e says, the increase in observed output over time is an observational effect. As kaberett explains, if you're talking about megayear timescales, Large Igneous Provinces will have a large impact on the timeseries. However, LIP and all continental eruptions (~1km^3 / ...

7

As with the answer to most things that involves consumption or absorption it's a question of degree, quantity and duration. Heat is energy that is being transferred. All life forms require a certain amount of heat to function and survive. Too much heat and not enough heat are detrimental to all life forms. Applying heat to food by cooking it kills most ...

6

If radioactive decay supplies only about half the Earth’s heat, what are the remaining sources of heat? Mostly it is residual heat energy from when the Earth was very young. The biggest source came from the kinetic energy of all the bodies, big and small, that collided to form the Earth being converted to heat. The differentiation of the Earth added even ...

6

Volcanoes erupt due to increase in pressure, within the magma chamber (often 3-10 km deep), due to exolusion of volatiles. The magma chamber is usually heated from below. Geothermal plants in volcanic regions exploit heat from hot water in the "shallow subsurface", few hundreds of meters deep (and rarely exceeding 1-2 km). So as far as your second last ...

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