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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Is there any correlation between La Niña/El Niño and seismic activity?

I've read in the past that extreme precipitation levels may have an effect on seismic activity, and wondered if anyone has ever analysed the La Niña / El Niño cycles to see if there are any ...
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10 votes
1 answer
192 views

Sediment layer chronology

In the new Cosmos series, Neil DeGrass Tyson in explaining different ways the age of the world has been determined, shows how sedimentary layers at the Grand Canyon are a fossil record of a lot of the ...
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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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44 votes
6 answers
106k views

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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11 votes
1 answer
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How can scientists be confident of isotope ratios in past eras and varied locations, used for radiometric dating?

Radiometric dating relies on past isotope ratio predictions being very reliable. However, this is not necessarily so. For example, in Uranium forensics, 235U and 238U ratios are about the same for ...
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13 votes
1 answer
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What lithologies are deemed most suitable for the storage of nuclear waste

I have visited storage- and test facilities that are within salt and clay (Opalinuston) lithologies. What are other lithologies that are considered for the storage of nuclear waste and what are their ...
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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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12 votes
1 answer
274 views

How to interpret the use of late and early Tertiary from older literature?

When reading older papers how should I interpret the use of "Late Tertiary" and "Early Tertiary"? Would these periods equate to Paleogene and Neogene, or was there a different accepted boundary age ...
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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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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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12 votes
3 answers
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Is Mount Everest currently becoming taller or shorter every year?

Is Mount Everest becoming taller or shorter every year? By how much? I would like an explanation in terms of tectonic plate movement if possible. Source: IamKatieHoffman.com
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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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11 votes
1 answer
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How can I tell if a rock is really petrified wood?

I found a rock in the Mojave desert and it resembles a tree branch including what appears to be wood grain. Is there some test or observation that can be done at home to conclusively answer my ...
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13 votes
2 answers
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How can the 'abiogenic oil' hypothesis be disproven?

We do know that complex hydrocarbons (e.g., tholins) exist in the outer Solar System. Some geologists maintain that at least some oil on Earth is of non-biological origin. The mainstream, though, ...
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28 votes
3 answers
41k views

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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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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18 votes
3 answers
4k views

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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21 votes
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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6 votes
1 answer
924 views

How can a non-geologist identify a rock? [closed]

I found a rock on a beach in north-east Evia, Greece. Half is light gray, and half is dark gray. There are white (or very light gray) thin lines that form swirls throughout, crossing the light/dark ...
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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
3 answers
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What is a good definition of the word "rock" for teaching?

Note that it needs to include coal and chert, therefore the common answer "a rock is made of minerals" is incomplete.
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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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14 votes
3 answers
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How and where do double-terminated crystals form?

How and where do double-terminated crystals form? Most terminated crystals form by 'growing' out of a rock. Which causes one side to be flat,(or whatever the shape of the rock it 'grew' out of was ...
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23 votes
2 answers
19k views

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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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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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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5 votes
0 answers
223 views

Is the Grand Canyon the "greatest" canyon in the world? [closed]

The Grand Canyon is nearly 446 km (300 miles) long, 29 km (18 miles) wide, and over 1,8 km (1 mile) deep. To the best of my knowledge, there is no other canyon of comparable size in the world. Is ...
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15 votes
1 answer
288 views

Are there situations where the groundwater table doesn't follow the morphology of the surface?

In most or all geological site reports I read, the groundwater table (of the uppermost groundwater layer) always followed the morphology of the surface. Is this always the case? Are there signs for ...
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10 votes
2 answers
25k views

What is the difference between a geologist and a geophysicist?

What are the main differences between geologists and geophysicists?
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5 votes
1 answer
325 views

Why is my ♦ hammer (i.e. diamond) so durable, but it can burn? [closed]

For those confused about the title, there's a joke that every moderator has a "diamond hammer" (diamond from the little by the username). In a chat discussion, it ...
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15 votes
2 answers
1k views

What causes "hydrocarbons" to take the form of petroleum versus natural gas?

"Hydrocarbons" are found in geological formations consisting of strata or layers of rocks. Specifically, they are formed from decomposed organic material (that contains carbon), that bonds with ...
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13 votes
1 answer
405 views

Which are the biggest methodological differences between the archaeological and geological approaches to stratigraphy?

Stratigraphy, or study of rock or soil layers (strata), was originally introduced as a branch of geology. However, it is often applied in other disciplines, especially in archaeology and paleonthology....
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20 votes
1 answer
819 views

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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35 votes
5 answers
9k views

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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44 votes
5 answers
29k views

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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22 votes
3 answers
429 views

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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20 votes
2 answers
886 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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14 votes
3 answers
293 views

How have global sedimentation rates changed over the last billion years?

Do we have a graph of how sedimentation rates changed over time?
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