Questions tagged [geology]

The science comprising the study of the rocks Earth is composed of, and the processes by which they change. Some subfields of geology are petrology, mineralogy, and geophysics.

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Are Richter-magnitude 10 earthquakes possible?

The largest earthquake since 1900 according to the United States Geological Survey (USGS) was Richter-9.5 magnitude quake in Chile in 1960. Are magnitude 10 earthquakes possible? If so, what is the ...
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How is the mass of the Earth determined?

According to textbook knowledge, the mass of the earth is about $6 × 10^{24}\,\mathrm{kg}$. How is this number determined when one cannot just weight the earth using regular scales?
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Farthest point from the center of the Earth

At first glance, this seems like such a simple question of "What's the highest point on Earth". However, I also know that the Earth isn't perfectly round. So that "highest point" may be in a ...
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Why do the Siberian methane craters have smooth vertical walls?

I expect most of you have heard of this by now. All the news is about whether or not they were formed by the release of methane, but it is also mysterious to me why this crater has jagged edges but ...
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3 answers
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Does gravity increase the closer to the core you get?

Or does the mantle and crust above you counteract the increase at one point and it actually decreases?
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5 answers
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Why is Earth's age given by dating meteorites rather than its own rocks?

Reading a course on Precambrian, I read that: Earth Age (around 4.5 billion years) is dated thanks to the meteorites hitting Earth during its formation rather than the inner materials composing the ...
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35 votes
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How and why did the oceans form on Earth but not on other planets?

Earth is the only planet in our solar system that has copious amounts of water on it. Where did this water come from and why is there so much water on Earth compared to every other planet in the ...
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32 votes
3 answers
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Is it true that earthquakes are not felt in a cave?

I took a tour of a cave in northern California last weekend. The tour guide asked us, "If an earthquake occurred, what would we feel in here?" My answer was, "fear," but she said we would feel ...
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29 votes
4 answers
8k views

Why is relative sea-level falling in Hudson Bay?

Why is the sea level in Hudson Bay decreasing so much? Hudson Bay is pretty far up north, much closer to glaciers. Would it make sense for it to recede at this level with sources of fresh water ...
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28 votes
3 answers
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Why is Earth's inner core made of an iron-nickel alloy?

This question has puzzled me for a while. I know that earth's mantle is made of different minerals, metals and rocks etc. and that has always made complete sense to me. But why is the inner core made ...
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27 votes
3 answers
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Is there sand in Antarctica?

There's a song "Blizzard's Never Seen the Desert's Sand". Given Antarctica is a desert, someone questioned the title's validity. BUT is there sand in Antarctica? I'd imagine yes as it's a pretty ...
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25 votes
1 answer
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How much of a mountain is below the surface?

Is there some kind of math rule for how much does a mountain extend (depth) below the surface? I found an article like this http://www.livescience.com/6595-depth-himalayan-mountain-roots-revealed....
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24 votes
2 answers
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Natural nuclear explosions

I'm aware of the Oklo reactor and other natural nuclear fission reactors, in which geological processes can lead to the formation of a sustained, self-regulating uranium fission reactor. Is it also ...
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Why does phosphate rock contain uranium?

I have been doing some research on the issue of phosphogypsum pollution. Phosphogypsum is a waste by-product formed with the "wet process" method of extraction of phosphoric acid out of ...
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23 votes
2 answers
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Why do crystals, like quartz and diamonds, form in different colors?

Some crystals, like quartz and diamonds, form in a variety of different colors. For example, quartz can be clear, 'foggy', pink, yellow, and even blue. What happens during the crystal's formation to ...
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22 votes
3 answers
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Where can obsidian be found?

Where is obsidian found? Is it typically found on the surface or underground? If underground, how far under (meters or feet would be perfect)? Also, is it found everywhere on Earth, or just in areas ...
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22 votes
6 answers
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Is there a difference between rock and stone?

I couldn't find the definitions from either source: Geology Dictionary Glossary of Geologic Terms
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22 votes
6 answers
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What was the first rock in the rock cycle?

I am an undergraduate student but I am a tutor at a High School, and one student asked me. Attempting to explain the rock cycle "if one rock turns into the other then which came first" my gut is ...
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2 answers
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Why are cobalt deposits so unevenly distributed?

The Democratic Republic of the Congo's Katanga Province contains almost 40% of the world's reserves of cobalt [1]. Why are deposits concentrated so strongly in such a small portion of the earth? I ...
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22 votes
2 answers
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How high can a mountain possibly get?

Mount Everest is 8,848 metres (29,028 feet) above sea level and is the result of a continental plate smashing into another continental plate. Can a tectonic process build a mountain that's even higher?...
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22 votes
3 answers
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Is fracking likely to produce earthquakes?

Post Christchurch-2011 earthquake, there was much concern that fracking in the surrounding areas might lead to further quakes, as was rumoured to have happened elsewhere in the world. Is there ...
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2 answers
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In what geological situations can I find gold?

I've heard that gold ore is often associated with quartz veins. What geological processes enable gold particles to naturally cluster together like this? What characteristics/properties should I look ...
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21 votes
2 answers
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What is the origin of the ocean's salt?

We know we cannot live without salt, but an investigation into the origins of ocean's salt leads one to believe that this issue is not fully resolved yet. What geological phenomenon caused the earth ...
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21 votes
1 answer
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Why are oceanic plates denser than continental plates?

In the theory of tectonic plates, at a convergent boundary between a continental plate and an oceanic plate, the denser plate usually subducts underneath the less dense plate. It is well known that ...
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21 votes
1 answer
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Is there geological evidence that the moon once collided with the Earth?

I've seen models in astronomy that show how the Earth-Moon system must have come together after a collision. However, I have not heard whether there is any actual physical evidence on Earth that ...
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Why are minerals found in "large" quantities and not scattered throughout the earth as individual atoms?

Heavier elements are created in stars. After stars die they scatter these heavier elements throughout the universe. These elements eventually gather to form planets. But why do we find "chunks" of ...
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21 votes
3 answers
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What caused the bend in the Emperor/Hawaii chain of islands, 45 million years ago?

What caused the bend in the Emperor/Hawaii chain of islands, 45 million years ago? Has there been any updates to this mystery I am unaware of? Are there any new theories that could potentially ...
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20 votes
2 answers
885 views

How does one measure what causes earthquakes?

I know that they occur when energy that was previously stored is released in seismic waves. But how is the energy stored in the earth in the first place, and what can trigger the release of such ...
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20 votes
3 answers
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What are rare earths and why do they cluster near alkaline magmatism?

'Rare earths' play a vital role in the modern economy, and they are becoming more of a point of focus in geopolitical realms. What are 'rare earths' and why do they appear to cluster in association ...
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20 votes
2 answers
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How do seismologists locate the epicenter and focus of an earthquake?

I know the focus of an earthquake is where the earthquake originated from, but what I could never figure out is, how to scientists find out where exactly the focus (and epicenter) are located?
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20 votes
1 answer
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What is the origin of the Montmartre mountain in Paris?

I have always wondered what is the origin of Montmartre mountain in Paris. What surprises me is that the whole area seems quite flat, and yet there's a very steep hill in the middle. How has that ...
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20 votes
1 answer
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What causes intra-plate faults, such as the New Madrid fault?

There's been news (some recently) about the New Madrid fault and other active intra-plate faults. For those living in the midwest of the United States, it's been a bit of a shock to learn they have ...
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19 votes
3 answers
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Are metals and other elements in every continent?

I originally thought that you can only find certain things like iron, copper, and other things in certain places in the world and deep in mines but I saw in a few YouTube videos that you can find iron ...
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19 votes
3 answers
3k views

Is the magma in one volcano different from the magma in every other volcano?

First off, a confession: I'm asking this question because of The Lord of the Rings. If you're not aware already, in the story, a magical ring can only be destroyed in a specific volcano. The reason ...
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19 votes
2 answers
2k views

Why does sea level correspond to boundary between oceanic and continental crust?

Is it a coincidence? the first is determined by the amount of water on the Earth and the second comes from evolution of tectonic plates. Still, oceans seem to fill exactly the oceanic crust.
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19 votes
2 answers
513 views

To what accuracy and precision do we know the volume of the Earth?

Satellites such as GOCE and GRACE measure the geoid with unprecedented accuracy. Altimeters can determine local surface elevation with millimetre-precision. This makes me wonder: to what precision ...
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19 votes
1 answer
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What are the physical upper bounds on the magnitude of an earthquake?

Given what we know about the physical mechanisms underlying earthquakes, what do the theoretical upper bounds on the magnitude of an earthquake look like? What physical phenomena impose those upper ...
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18 votes
3 answers
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How did Earth's plate tectonics start?

Plate tectonics is a theory which describes Earth's lithosphere as being composed of distinct plates which are able to move atop of the underlying asthenosphere. At plate boundaries, this movement ...
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18 votes
3 answers
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What is the difference between eluvium and alluvium?

I was reading about kimberlite on Wikipedia and it mentioned eluvium. I've heard of alluvium, alluvial fans, alluvial deposits, etc. However, when I looked up eluvium, it sounded exactly like alluvium....
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18 votes
3 answers
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When can taste be used to help identify rocks?

Taste can be used to distinguish halite (ordinary salt) from sylvite (which has some bitterness) and siltstone from mudstone (the latter has a creamy texture while the grains of the former can be felt)...
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18 votes
1 answer
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How long until Earth's core solidifies?

How much longer does Earth have until the core turns solid? Does global warming change these estimates at all?
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17 votes
2 answers
437 views

Why did people draw so many continuous squares in the sand on the beach at Cape Juby?

At Cape Juby, Morocco, we can see with Google Maps a rectangle of 3 km long, in which there is hundreds of little squares. What method was used to draw these squares on the sand? More importantly, why ...
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17 votes
2 answers
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What determines a mineral's hardness?

Mohs Hardness Scale is basically a measurement of the hardness of a material, or more specific, a rock or mineral. But I have never been able to figure out why some minerals are harder than others.
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17 votes
3 answers
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Is there a reason most mountain ranges seem to run parallel to coastlines?

Eyeballing a map of the world, it seems that most mountain ranges that don't occur along continental fault lines run parallel to coastlines. Is there a reason for this?
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17 votes
2 answers
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Why does a subduction zone produce a serpentinization diapir rather than volcanism?

The classic Troodos Ophiolite in Cyprus has been uplifted by a 'serpentinization event'. Upper mantle (peridotite) has been serpentinized creating a buoyant diapir. This has uplifted the ocean crust ...
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16 votes
3 answers
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How do geologists find ore deposits?

From my research, there is lots of information on how to extract ore, but I can't find any information on how these ore deposits are found in the first place, apart from 'looking for surface ...
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16 votes
1 answer
4k views

How old is the Earth?

According to most articles I've read online, the estimated age of Earth is 4.5 billion years. Question: How old is the Earth? So I actually want to confirm that this is the case. Maybe there are ...
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16 votes
2 answers
67k views

Are the processes of the rock cycle currently in dynamic equilibrium?

The standard representation of the rock cycle usually looks like this: Does each stage of the rock cycle currently balance? That is, are the various processes in dynamic equilibrium, so that the ...
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16 votes
2 answers
377 views

Did the impact event that caused the Chicxulub-Crater definitively and single-handedly cause the Cretaceous-Paleogene extinction?

Opinions abound on the web. What is the state of the current science regarding this theory and what is the best evidence? Is the theory gaining or losing traction? If it's losing what's the best of ...
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16 votes
1 answer
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What are the differences between geology, petrology, and lithology?

What differences are there between geology, petrology, and lithology? If I were to get into any of those fields, what exactly would I be studying? Also, are petrology and lithology just branches of ...
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