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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Earth's ocean basins

Was Earth's sea-floor always carved with the numerous geological features that we see today, or was it at some point flat and boring as Mars is today?
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Can geochemical anomalies of stream sediment samples be used directly for mapping targets?

We know that geochemical dispersion in stream sediment is much widespread, facilitating discovering mineral targets in a regional scale. However, we also know that there should be discrepancy in space ...
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Cause of Wallace line

First off, I am a biologist, not an earth scientist. Very recently I heard about a very interesting biological phenomenon that has its origins rooted in geology : The Wallace Line. From a ...
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Why do some earthquakes and volcanoes occur within plates?

I know that volcanoes and earthquakes occur on plate margins. But, do some of them also occur within plates?
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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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Can a braided fluvial create thick relatively continuous siltstone beds?

I am attempting to interpret an outcrop I went to. I suggested it was created by a braided fluvial. The one thing I cannot explain are prominent alternating siltstone beds with the sandstone beds. ...
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Can I regard the grayscale of a RGB color image as a panchromatic image?

Here I have a remote sensing dataset with many bands (e.g., blue, green, red, ...), and I use the blue, green and red bands to get a true color image. I want to know if I can get a panchromatic band ...
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Isotopic dating of metamorphic rocks

I read in my physical geology textbook that sedimentary rocks cannot be dated using isotopic dating, because they are formed from fragments of other rocks and minerals, which if you were the subject ...
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Sedimentology (Particle size distribution parameters)

The Inclusive graphic standard deviation (sorting) value of this claystone sample is negative (-1.29). Is this right to be considered as very well sorting ? However, the bivariate plots of ...
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Origin of Andaman and Nicobar islands

Are Andaman and Nicobar islands in Indian ocean a continuation of Alpide-Himalayan orogeny or are they volcanic in origin?
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Why were Fe-oxides not usually used for finding skarn Fe ore deposits in geochemical exploration?

I found that Fe-oxides were usually not used for vectoring Fe mineral deposits of skarn type in geochemical exploration. As an indicator element, the common practice told us Fe-oxides should be 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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If the Kola Superdeep Borehole were opened today, what would come out of it?

The BBC News article The Deepest Hole we have Ever dug says: This is the Kola Superdeep Borehole, the deepest man made hole on Earth and deepest artificial point on Earth. The 40,230ft-deep (12.2km) ...
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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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Can ultrasounds be used to map the density of large underground regions?

This question arose from a related one at Physics.SE, along with my own personal quest to better understand mineralogical prospecting. I want to know if some kind of ultrasound machine can determine ...
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Why does Morocco have so much phosphate?

I read that Morocco/Western Sahara has 75% of the world's known phosphate reserves, but I couldn't find an explanation of what mineral is responsible for it and how it all ended up there.
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What are some effective approaches to enhancing fossils in amateur found rocks?

My stepson found this rock on the shore of Lake Michigan and gave it to my son who loves fossils. I'd like to really bring out those fossils. What are some techniques that I can try that won't ...
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Water flows under the headwater and soil liquefaction has formed

A retaining wall 40 cm thick with variable height (thin-walled corner) is being built in the mountainous area. At the time of the geotechnical survey and design, there was no reservoir next to the ...
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How did these holes form in the rock? [closed]

I've been trying to figure out how these holes formed in the rock. These pictures were taken in Quebec, Canada on small lake in cottage country. The strange thing is that they are almost both ...
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What is the pressure at the center of the Earth?

In the question Does gravity increase the closer to the core you get?, it was determined that gravity reduces to zero at the center of the Earth. That is logical. However if pressure is proportional ...
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Has there ever been a case where we have found what appears to be a prehistoric fossil but have no way of dating it?

I find that when ever I learn of a new fossil, the age of said fossil is always mentioned. This perplexes me given how intuitively rare it seems to have radioactive material to date a formation. I ...
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Did geologists determine the age of rocks and fossils before the advent of modern scientific dating methods?

Did geologists determine the age of rocks and fossils before the advent of modern scientific dating methods such as radiometric, electron spin resonance and thermoluminescence? If they did, does ...
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What affects where a terrain will be rocky or grassy?

I’m working on a terrain generator and I now need to color the terrain to be rock, grass, or snow. Ignoring snow for now, at first I thought I’d make flatter areas grass and make steeper areas rock. ...
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Do carbon dioxide hydrates exist in nature?

Do CO2 hydrates exist in nature? If so, how much carbon could they contain?
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Fossil ID: possible fauna fossil, from Perlis, Malaysia

I found this fossil while doing my fieldwork in limestone area. Description below may help to identify it. Location: NW Perlis, Malaysia (Setul Formation). Hilly Area. My Observation: Have a curly ...
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Rapidly rising land after rain seen in India? What can cause this?

I came across a video where a piece of land was seen rising very rapidly after rain. The land got elevated within a few minutes by atleast a meter. Can anyone suggest possible mechanisms? I am sharing ...
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At what theoretical depth of sand would pressure turn the sand into rock?

Thinking about the movie Dune (this is not a sci fi question) got me to wondering. In the theoretical situation where you had a desert of sand with an unlimited depth here on Earth. At what depth ...
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What is the global distribution of oil filled geodes?

In a general 40 mile radius of Keokuk, Iowa many sedimentary geodes can be found. They are abundant in the Warsaw Formation with the type section at Geode Glenn in Warsaw, Illinois. In one specific ...
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Why are the mountains predominately grey or dark brown?

Observing many photos of mountains one can assume that most of the mountains are grey or brown. See also the mountain article at Wikipedia. There are however several ways a mountain can form, which ...
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Can we separate a sandy, clayey & salt layer on basis of their rheological properties?

Since, given enough compaction, salt is able to behave like a fluid & buoyant too if it's overlain by a higher density rock (it could be fine grained clay or a sandy sequence). But in another case,...
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Is it incredibly unlikely that industrial societies emerge elsewhere in the galaxy due to lack of petroleum or similar substance?

Not sure where to post this question, but it struck me the other day that the major driving force behind our modern industrial society is owed nearly entirely to the harnessing of petroleum power in ...
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What significant factors influencing geological change are still occurring?

I am teaching a secondary school course on my state's local history. The textbook begins with the history of the first humans, yet I think it is unfair not to start back much earlier, introducing the ...
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How can we know the past height of mountains?

In Feynman Lectures on Physics Volume I, Feynman talks about the relation between Physics and Geology. He says “Mountains are no lower today, on the average, than they were in the past”. Through what ...
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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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How could this pyramidal Mountain have been formed?

How could this pyramidal peak have been formed in Antarctica? Little is known about it as far as I know but what is known is that its miles away from any existing plate boundary and its shape is also ...
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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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Are we observing sedimentary rock formation today?

For instance, are we able to see the microscopic accumulation of shale or limestone? Can anyone reference me to sandstone formation observation, that would have to occur more rapidly. I’ve heard it ...
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How much would the ground be displaced in a magnitude 11 earthquake?

In a magnitude 5 earthquake, the ground shakes violently and it's often impossible to stay upright. This is caused by about 50-120 cm of displacement of the ground. But how much would the ground move ...
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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 ...
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How can I learn to spot fossils and fossil-bearing rocks on the Jurassic coast?

Due to a pleasant change in my circumstances, I have been to Lyme Regis several times recently, and it seems as though I'm going to be a regular visitor over the next few years. As a former biologist ...
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How is geological time divided into units?

Earth's history is divided into eons, which are divided into eras, which are divided into periods etc. Consecutive time units differ in their geology and/or fossil species. But what events are the ...
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How to distinguish an explosion crater from an impact crater?

(How) Is it possible to tell the difference between a man made explosive crater and an impact crater?
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How do hematite and magnetite form?

I want to understand the conditions under which hematite $\ce{Fe_2O_3}$ and magnetite $\ce{Fe_3O_4}$ form in nature. The linked Wikipedia articles explain various conditions under which they form, but ...
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What methods do geologists employ to detemine the age of a petroleum deposit?

Petroleum is not considered a rock, but it is formed by a process, so it has an age. What methods do geologists employ to determine the age of a petroleum deposit?
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Why are South African mountains short and flat?

I drove through South Africa from Cape Town to Mozambique and noticed that almost all heights and mountains were no higher than approx 200-400 meters and had a flat top, just like the iconic Table ...
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How strong/hard are speleothems?

I want to know how hard or strong typical speleothems are. For example, could an average man break off a small stalactite or soda straw? If they're very hard, how do they compare to bone?
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Artifical Ore Genesis?

From my understanding, the formation of ores can be reduced to a simple three-step process of the removal of minerals from a source via some mechanism, the transportation of these minerals, and ...
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1answer
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Can a lightning strike ionise the material it strikes?

I know lightning strikes ionise the air, but I'm looking into geology, specifically amethyst, and found that it gets its colour partially from trivalent iron, iron(III), Fe 3+, whatever you want to ...
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How fast does sand degrade into silt, and silt into clay?

I am talking to some students about how soil changes, and I've heard from soil samplers that the texture of the soil, i.e. whether it is sand, silt or clay, doesn't change in a human lifetime. It ...
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regarding four-way closure in structural geology

I am a little bit confused on the two concepts in structural geology, i.e., what is the relationship of anticline and four-way closure. My understanding is that anticline belongs to four-way closure. ...

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