# Tag Info

33

We know the the size of the inner core through seismology. From my answer to this question: How are subsurface wave speeds determined without subsurface sensors?, we can determine the speeds of the different layers of earth. Pictured below is a diagram of raypaths going through the earth from the 1994 Northridge Earthquake in Southern California: (image ...

31

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 ...

20

The best argument I've heard supporting strong skepticism of plumes, if not total dismissal, is that the theory is too flexible. To put it more bluntly, this amounts to saying that it is unfalsifiable and therefore not helpful (in Popper's words, "A theory that explains everything, explains nothing."). Erik Lundin, a Norwegian geologist, is a fairly ...

19

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

It's an interesting question, but in practice I think it's impossible to answer. It's very difficult to measure the rates of many of those processes, and the divisions between rock types can be quite ill-defined (for example, in migmatites). There's no scientific instrument we can point at a chunk of the earth which will tell us "in this region, 29.4 ...

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 ...

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

I am going to assume that you are referring to recent new stories with titles like "Rare Diamond Confirms That Earth's Mantle Holds an Ocean's Worth of Water" (Scientific America). These articles are referring to research published in Nature: Pearson, D. G. et al. (2014). The researchers found an inclusion of ringwoodite inside a diamond. Here is a quote ...

16

This is a complex question, and I cannot give you a complete answer I'd like to point out that there is a very important article published in February of this year on the subject: volcanoes are in an eruptable state very very short periods of time in the geologic timescale; the mobilization of magma is very rapid but its storage is kept near, but under the ...

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 ...

14

This isn't that difficult, but anything is if you start from the wrong place. Let's derive this thing: $$P = \frac{F}{A}$$ Where $P$ is pressure, and $A$ is the area the force is pushing down on. Let's take a break and derive the units first, just so we know our end derivation is correct; $F$ is in Newtons, which comes out to \$\mathrm{kg} \times \frac{\...

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

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

Please take into consideration that I am not a specialist of plate tectonics, just a paleontologist. Although this cycle is often nicknamed the Wilson cycle (probably because of Wilson, 1966), the idea that supercontinent formed cyclically every 440Ma was advanced by Worsley et al. 1984 (see review on the subject by Nance & Murphy 2013). The mechanism ...

13

To the best of our knowledge, sea-level is rising because the volume of water is increasing. There is substantial local variation in sea-level change; it's falling in some parts of Canada. But of the dozens of controls on local and global sea-level, the net effect is currently an average global rise of about 3 mm/y. It's not really 'a riddle'. The ...

12

Disclaimer: This is a partial answer given that my background is modeling of the ocean. I hope that some mantle convection modelers can complement this answer. The question is good but the answer is complex. The short answer is: No, they are not the same. Simply because computationally it would not make sense. I will try my best to break it apart and make ...

12

Yellowstone is thought to be above a mantle plume, of with there are tens to hundreds on our planet, although there is plenty of debate on this matter. The exact nature of mantle plumes is a huge area of hotly contested research, but generally the are thought to be large melts originally sourced from the D'' layer (core / mantle boundary). Below the park, ...

12

As you said, the Andean belt is divided into four segments, usually called the northern, central, southern, and austral volcanic zones (NVZ, CVZ, SVZ and AVZ, respectively; your map lacks the AVZ). This has been interpreted as a difference in the angle of subduction. Under the active zones, the subducting plate (called "slab") sinks into the mantle, ...

11

Is it true that Earth's outercore rotates in the opposite direction to Earth's inner-core? No. You misread a badly written for-the-masses science article. The article summary is at best rather confusing and misleading. It invites a reader to misinterpret what's going on. So what's really going on? It's simple, conceptually. The mantle, outer core, and ...

10

This is a very good question Inkenbrandt. It is quite common for even some graduate students to think that the majority of partial-melting comes from the slab: when it is the the mantle above the fore-arc, in the volcanic region, where most of the partial melting occurs. Lets think about this mathematically: you say yourself that you realize that subduction ...

10

Mathematics and computer science are exact sciences. If something is discovered and known, it is not wrong. With time, there may be better or new ways of doing something, but the old stuff is still correct. This is why you can get a textbook from the 60s and study it. Cauchy's laws are still correct and Euler's theorem is still correct. This is not the case ...

9

Scientists used the seismic waves created by earthquakes bouncing off the core to map out the approximate size of the earth's inner core. The materials that constituted the core were guessed with the thinking that because it was once liquid, the heavier elements like iron and nickel were able to sink down into the center. It probably even has vast amounts ...

9

The high values obtained when estimating the Rayleigh number for the mantle indicates that convection there is vigorous, and that convection is responsible for almost all the heat transported from the deep interior to the surface. Similar systems set up in the laboratory can develop 'plume-like' patterns of convective flow, and so mantle plumes are a ...

9

I am afraid that you aren't being specific enough to really answer your question: What about mountain chians valleys and hills are you interested in? There are simple and complex models dating back from the 1960s to present. Are you interested in learning about the material properties of the crust, or just topography in general? What about weathering effects?...

8

The answer is that there are more forces than just the momentum of the earth at play. The electromagnetic force generated by the core is pushing on itself, in fact: "The fact that Earth's internal magnetic field changes slowly, over a timescale of decades, means that the electromagnetic force responsible for pushing the inner and outer cores will itself ...

8

This statement is referring to depths within the crust where the lithostatic pressure is sufficiently high to suppress the formation of dilatant fractures. Rock is a brittle material, and if loaded to failure while under little or no confining pressure, it may fail by the growth of mode-I fractures oriented normal to the least compressive stress. At depth in ...

8

This statement is known as the Wallace-Bott hypothesis. It is mostly valid for reactivated faults rather than fresh rocks(where cohesion comes into play). It says that the slip in a fault plane will occur along the direction of maximum shear stress. So we have a stress vector acting on a fault plane(the direction given by the direction of force), it has ...

7

The tiger stripes of Enceladus are thought to be a result of this moon's unusual chemical composition, as opposed to any mineral heterogeneity or thermodynamic perturbations occurring due to the phase change near the rocky core. Ammonia has been found indirectly to exist on Enceladus and the unique ammonia-water composition of Enceladus is thought to give ...

7

The only similarity that they are fluids and therefore NS applies. Actually, to be fair mantle is solid as it allows shear waves to propagate through. However, on geologic time scales it behaves like a viscous fluid and can be modeled as such. Circulation models solve compressible (non-hydrostatic) Euler equations where as mantle convection is governed by ...

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