56 votes
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Farthest point from the center of the Earth

It's Chimborazo, Ecuador, but only just, beating Huascarán, Peru, by less than 50 metres. Both are over 2 km 'higher' than Everest. I made a plot of some mountains — height above centre of the earth ...
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56 votes

Why is the pond in my backyard not frozen when it is -15 °C (5 °F) outside?

Water is a rather strange substance. With most substances, the solid phase is denser than is the liquid phase. This is not the case with water. Ice is less dense than liquid water. A side effect of ...
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54 votes
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Does gravity increase the closer to the core you get?

The below figure, taken from Wikipedia shows a model of the free fall acceleration, i.e., 'gravity'. The left-most point corresponds to the center of the Earth; then further right at $6.3\cdot1000$ km ...
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  • 1,959
53 votes
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Why is the pond in my backyard not frozen when it is -15 °C (5 °F) outside?

Water melts at 0 °C (32 °F) but freezing is a more complicated affair. It is safe to say water gains the ability to freeze at 0 °C, but it can get much cooler before it actually does so resulting in ...
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42 votes
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Where on Earth is the magnetic field intensity stronger?

If we consider only the magnetic field generated by natural sources, and not the ones generated by human activities. The general trend is that higher intensities of the magnetic field happen close to ...
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41 votes
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How is the mass of the Earth determined?

According to Newton's Law of Gravity based on attractive force (gravitational force) that two masses exert on each other: $$F=\frac{GmM}{r^2}$$ Where: $F$ is the gravitational force $G = 6.67 \times ...
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  • 688
38 votes

How is the mass of the Earth determined?

Note: I updated this answer to include a description of the historical techniques. Historical Techniques Newton developed his theory of gravitation primarily to explain the motions of the bodies ...
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37 votes

Are Richter-magnitude 10 earthquakes possible?

Adding a little bit of practical data to the above answer about the Gutenberg-Richter relationship, here is a plot of the per-year cumulative probability of earthquakes in a particular province in ...
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  • 1,374
35 votes

Are Richter-magnitude 10 earthquakes possible?

Are magnitude 10 earthquakes possible? The idea of a “Mega-Quake” – an earthquake of magnitude 10 or larger – while theoretically possible—is very highly unlikely. Earthquake magnitude is based ...
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  • 4,561
34 votes
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Are Richter-magnitude 10 earthquakes possible?

Magnitude 10 earthquakes are indeed possible, but very very unlikely. You see the frequency of an Earthquake is given by the Gutenberg-Richter law: $$N = 10^{a-bM}$$ where $N$ is the number of ...
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  • 6,356
33 votes
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How can we determine the size and composition of Earth's inner core?

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 ...
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32 votes
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Could the Earth's core lose its heat?

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). ...
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32 votes
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Why is Earth's inner core solid?

Earth's inner core is solid even though the temperature is so high because the pressure is also very high. According to the Wikipedia article on the Earth's inner core, the temperature at the center ...
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28 votes
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Where is the calmest place on Earth?

The main resistance that winds have to their movements comes from the topography and surface obstacles. Therefore, as a general rule the closer to the surface the less wind you will find. But I guess ...
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26 votes
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Is it true that earthquakes are not felt in a cave?

Ground motion results due to passage of elastic waves. Now there are different kinds of waves, e.g., P waves, S waves, surface waves, etc. Most of the shaking (and therefore damage) is caused by ...
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  • 2,361
23 votes
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What causes the Earth to have magnetic poles?

Well, firstly it's important to recognise that the poles are merely the extremities of the shape of a magnetic field - the earth's magnetic field. All magnetic fields have polarities as such. ...
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23 votes
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Why are oceanic plates denser than continental plates?

Ocean lithosphere (geophysical definition of crust + upper mantle that acts as a 'plate') is primarily of basaltic composition - the upper levels are basalt and the lower levels are gabbro. The top ...
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23 votes

Farthest point from the center of the Earth

Mount Chimborazo, which is 6,268 meters above sea level and within 1.5 degrees of the equator. More specifically, according to Dr. Milbert, Chief Geodesist, NOAA, National Geodetic Survey and Dr. ...
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  • 5,892
23 votes

What would be the first thing which will render the Earth uninhabitable?

I'll try to put time scales on each of these events. The Sun as a red giant - 5 to 6 billion years$^1$ The Sun is currently on the main sequence, which means that it's a "full grown" star - think of ...
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23 votes
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Why does sea level correspond to boundary between oceanic and continental crust?

Sea-level only sort-of corresponds to the oceanic–continental crust boundary. In depth, they don't correspond at all: It's the same story at an active margin: the plate boundary at a subduction zone ...
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22 votes

Why is the pond in my backyard not frozen when it is -15 °C (5 °F) outside?

Due to convection (the cold water sinks while the warm water rises), the entire pond needs to be brought to near-freezing temperatures before the surface can freeze. With only the top of the pond in ...
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22 votes
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Does gravity differ from place to place on Earth

There is an entire field of Geophysics called gravimetry dedicated to measuring the magnitude of the gravitational field. First, we should distinguish between weight (a force) and gravity (an ...
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22 votes
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Taking into account the decay products of transuranic elements, are the world's uranium reserves growing or shrinking?

Let's start with the easy question: given our current known reserves of transuranic elements and again taking into account their decay products, where will the greatest uranium reserves be in, say, ...
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21 votes

Why is Earth's inner core solid?

In addition to the answers below and my comment above, I believe the following phase diagram, from DavePhd's answer here, sourced from here, is more appropriate for the pressure levels near the Earth'...
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  • 7,346
21 votes
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Why is Earth's inner core made of an iron-nickel alloy?

The first thing you should think about is how the accretionary disk cooled and the cosmochemical constraints this put on Earth (But I am not going into details here). From studying meteorites it is ...
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  • 3,876
21 votes

Are Richter-magnitude 10 earthquakes possible?

Perhaps this is not what you had in mind, but it seems to be generally agreed that the Chicxulub asteroid impact generated earthquakes in excess of magnitude 10.
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21 votes
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How long until Earth's core solidifies?

Global warming has to do with the surface only, and at best involves changes of 20 degrees at the outside extreme, in comparison to the earth's core, which is as hot as the surface of the sun. For ...
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20 votes
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Is fracking likely to produce earthquakes?

It's not too too likely, but it can happen. A few earthquakes have either been attributed to fracking, or the wastewater produced from fracking. According to the USGS (for more information, visit ...
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  • 1,940
20 votes
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What are some of the strongest theories against the existence of mantle plumes?

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 ...
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