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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8
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1answer
805 views

What is this Cape Breton rock? [closed]

What is this rock? I found it in Cape Breton, Canada
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2answers
340 views

What is the reasoning behind the statement “Faulting will occur along the plane where the shear stress is the highest”?

In "An Introduction to Seismology, Earthquakes and Earth Structure", authors Seth Stein and Michael Wysession made the statement: "Faulting will occur along the plane where the shear stress is the ...
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What would the geology and climate of a supposed landmass near the pole be like, assuming a thoroughly warmer planet? [closed]

I am designing a fantasy setting for pen-and-paper role-playing (and potential novel) purposes. I have decided that a continent be situated right on a Pole of some imaginary planet with axial tilt ...
20
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1answer
483 views

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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How has the relative ratio of igneous, sedimentary, and metamorphic rocks changed over Earth's history? [duplicate]

Has the relative ratio of sedimentary over igneous rocks increased, simply as a result of more and more of the Earth's rock being exposed to sedimentary processes? Or has it increased only for the ...
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2answers
253 views

How to determine how long ago a rock was broken?

I know that there are techniques that help scientists determine the age of a rock. But is it also possible to determine how long ago a rock was broken? For example, how could we date the formation of ...
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685 views

If all the sand in the Saharan Desert were to be removed, what would the remaining landscape look like? [closed]

Would it look like any other region of the planet?
8
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1answer
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What is this brown and white rock? [closed]

We found this rock in our backyard. Could someone please tell me what it could be?
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2answers
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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 ...
11
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1answer
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Determining a rock age using volcanic ash layer

I wanted to know if volcanic ash deposits found in the geologic record are most useful in correlating the age of rock layers if the volcanic ash was distributed over a large area during a short period ...
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2answers
12k views

How do I derive the formula for lithostatic (overburden) pressure?

The title pretty much says it. I have the formula: $P = \rho g h$ where $\rho$ is the density, $h$ is how deep the pressure is in the Earth and $g$ is the gravitational acceleration(?). I don't get ...
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3answers
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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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6answers
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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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562 views

What's the geological period of the birth of the river Ganges?

Avatarana or Descent of the Ganges (extracted from Wikipedia): "In late May or early June every year, Hindus celebrate the avatarana or descent of the Ganges from heaven to earth." There are ...
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1answer
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Is it true that “[sand] grains in the Coconino Sandstone come from the Appalachian Mountains”?

The Creation Museum is a terrifying place for scientists of all stripes. One of their exhibits is the "Flood Geology" exhibit, which purports to explain how a flood of (literally) Biblical proportions ...
14
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1answer
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In what sense did the Oklo reactor “trap” its own nuclear waste?

A number of popular writings on the natural fission reactor at Oklo, Gabon (e.g. here) state that some of the energetic byproducts (krypton and xenon, presumably 85Kr and 133Xe) of the reactor were "...
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1answer
118 views

Why would a suite of related rocks have one anomalous sample?

I have a suite of rocks that have nearly identical major element chemistry, but a single sample has quite different trace element concentrations. All the rocks are trachydacites. I know the analysis ...
12
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1answer
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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 ...
10
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1answer
160 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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1answer
326 views

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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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 ...
11
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1answer
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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 ...
12
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1answer
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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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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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1answer
250 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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2answers
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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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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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3answers
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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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1answer
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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 ...
11
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1answer
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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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1answer
214 views

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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3answers
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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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1answer
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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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2answers
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How did tectonic plates originally come to form?

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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2answers
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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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1answer
903 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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2answers
333 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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2answers
792 views

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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2answers
2k views

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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3answers
4k views

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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2answers
14k 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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3answers
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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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1answer
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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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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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1answer
230 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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2answers
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What is the difference between a geologist and a geophysicist?

What are the main differences between geologists and geophysicists?
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5answers
1k views

What type of rock is this that is light colored with greenish crystals? [closed]

I found this rock. It is probably a very common rock but could an expert please tell me what rock this is?
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1answer
318 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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1answer
868 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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1answer
362 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....