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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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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Are there any known global effects of the Mediterranean sea evaporation and refilling?

This is a broad subject I realize, but I'm looking for specific geologically observed answers of global effects elsewhere, between about 5.96 and 5.33 million years ago when the Mediterranean sea was ...
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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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High-resolution laterolog array tool

Does anybody know if it is necessary to apply corrections to the reading given by this logging tool? Corrections such as bed thickness, borehole diameter, invasion, etc.? If so, is there anywhere I ...
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Did an impact crater cause the formation of the gas fields in north eastern South Australia

In the paper High Impact Reservoirs, the authors claim that impact craters have lead to both the creation and destruction of petroleum source rocks, reservoirs and traps. Recently it was announced ...
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Will a Mohs hardness scratch pen need to be replaced or resharpened?

I am considering buying a set of Mohs hardness scratch pens (aka hardness picks). As a hobbyist the price is quite high, starting at 300 USD and upwards for a complete set. I can accept this price if ...
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Formation of Hematite on Mars via Perchlorates as an Oxidizer

Hematite on Mars is generally thought to have formed either in pools of water or from volcanic activity. A comment to the answer to the question: How do hematite and magnetite form? states that ...
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Dating fluvial terraces with $^{10}\rm{Be}$

I've completed part A of the question below. Dating fluvial terraces with $^{10}\rm{Be}$ One way to determine the age of an alluvial deposit is to collect a series of samples from a range of depths, ...
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What is causing the crustal extension exhibited by the Basin and Range province in western North America?

Is there any link with the subduction of the Farallon Plate and the associated spreading center?
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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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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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How do the Andes get so high?

I'm interested in the limiting factors on the height of mountains. There is a very good explanation at https://www.quora.com/How-tall-can-a-mountain-become-on-Earth-Neil-deGrasse-Tyson-says-Mount-...
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Why is Cambrian denoted with such a weird symbol?

I find Ꞓ such an odd-looking symbol. What's the historical significance, etc, of that symbol? Latin letter C with bar My understanding is, C was the Carboniferous, K for Cretaceous... why not ...
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How do you choose appropriate parameters for a lowpass filter when filtering a Bouguer anomaly?

I am trying to filter my Bouguer anomaly data to remove the short wavelength features. I have created a lowpass filter to achieve this, but I am wondering how I can more objectively choose my cutoff ...
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When will the weight of melted polar ice release the (currently stuck) subduction of the oceanic plate West of the Oregon coast?

Melted polar ice water makes the oceans deeper on average. The extra water on top of the oceanic plates makes them sink relative to the continental plates. This relative vertical displacement will ...
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How do I generate a Moho depth model from seismic refraction data?

There are several permanent seismograph stations in Eastern Canada that have been recording arrival times for over 25 years. Using refracted Pn arrival times from natural earthquakes I would like to ...
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How big does something have to be to cause an atmospheric event upon entry to the Earth's atmosphere?

The question is about a foreign object, ranging from an asteroid to a spaceship. How large does it have to be in order for its presence to start messing with the weather patterns, causing the like of ...
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How long do geysers typically stay active in Yellowstone?

Old faithful still erupts regularly, but at some point conditions in geology will change and it will cease activity. Wikipedia says that ~1300 geysers have erupted in Yellowstone, but only 1/3 of ...
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What causes a change in composition from basanite to nephelinite?

Can the change in composition from basanite to nephelinite (i.e. increasing alkalis with decreasing SiO2) be explained in terms of fractional crystallisation, or only by a decreasing degree of partial ...
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Earth's inner core has an inner core inside itself. Are there three inner cores?

The Seeker.com article Earth's Inner Core Has Its Own Inner Core states that researchers at University of Illinois and Nanjing University in China have made a bizarre discovery. They've found that ...
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I have found this structure in thin section. What is it?

I have been observing a nepheline specimen under polarized light and found some interesting places. I have taken several images. The first shows a micro-geode with parallel polarizers, second with ...
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Definitive values that classifies a rock as having “low”, “medium”, and “high” -strength, -hardness, -toughness, and -consolidation?

Question: Are there any widely accepted published values (or ranges) that classifies a rock as having “low” “medium” “high” -strength, -hardness, -toughness, and -consolidation (cementation or ...
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Lithologic and hydrostratigraphic logs for the Deccan volcanic province, India

I need data on depth/thickness of of different lithologic units under Deccan Volcanic Province in MP, Maharashtra and Gujarat. For this if anyone can help in providing help in obtaining well log data ...
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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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Patterns on Basalt

These Basalt rocks were hand cracked and used to build the walls on my home. Many of these rocks have these semi circular pattern, made of the basalt itself. It's just a bit darker than the rest of ...
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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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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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Hypothetically, in the near future, could gas hydrate pingos erupt?

Could gas hydrate pingos erupt? If so, how quickly? And how much CH4 could they release? I'm sorry if the questions sounds silly. I'm new here and I don't know much about gas hydrates and oceanography....
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How would one go about drawing the contour lines for this map in order to draw the cross section?

Good Day. We Received this map as practice for our Geology university module and I have no idea how to draw the strike lines where the different heights intersect the different rock types in order to ...
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Looking for videos/GIFs of petrification/permineralization

Do you know of any good animations, videos, or GIFs of petrification/permineralization? For some students verbal and written explanations don’t work, they don't always visualize well. So it’d be ...
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4 votes
2 answers
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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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How do people determine initial ratio of the parent nuclide and daughter product in radiometric dating?

I understand that we have zircon crystals that prevent entering or leaving of nuclide or lead after forming. But how cand we understand what was the initial ratio?
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how best to preserve the color of my amethyst geode?

Will bright indirect light cause an amethyst crystal to fade? How about an overhead LED light? How is best to preserve the color of my amethyst geode? Thank you!
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Is there a large undersea caldera in the Azores?

There looks like a large undersea circular feature (Google maps) about 120km across with its north edge on Sao Miguel Island and its south edge on Santa Maria Island. Has any work been done to say ...
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4 votes
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Presence of cross stratified conglomerates in fan deltas

Why are cross stratified conglomerates found in deposits of fan deltas? I know that fan deltas are alluvial fans that deposit directly into the sea, hence they are poorly sorted.But could not ...
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4 votes
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What gravitational evidence do we have to counter the idea that oceans are formed when continents sink?

Is there some evidence for this based on gravity anomalies? I think I know how to tell if a mountain or structure is compensated based on bougeur and free air anomalies, but this really has me ...
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4 votes
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For slab rollback, what allows the subducting plate to begin descending at a steeper incline?

I recently learned about slab rollback, specifically of the Juan de Fuca plate subducting underneath the North American plate. From what I understand, the subducting plate over time begins descending ...
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Is the Ethiopian Plateau uplift still ongoing?

The rift zones around the Ethiopian Plateau, Mid Ethiopian Rift, are stil tectonically active since Somalia is separating from Nubia at a rate of 6–7 mm annually[1], and Arabia is rotating counter-...
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How to differentiate between normal and reverse fault, given a stress tensor?

I want to generate synthetic fault slip data using a known stress tensor. I am using a rotation matrix to get the orientation of the principal stress axes, and rotating the tensor [1 0 0, 0 phi 0, 0 ...
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4 votes
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How to integrate dry wells into groundwater level mapping automatically (inequality constraints on the interpolation)?

I'm interested in automating spatial interpolation of groundwater level measurements. I'm wondering if anyone knows a method for automatically taking into account things like dry wells, where I can't ...
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Why is the Colorado Plateau so stable?

The Colorado Plateau somehow has avoided all the tectonic activity around it over hundreds of millions of years. Is it just luck, or is there something about that chunk of crust? I have toured the ...
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3 votes
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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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3 votes
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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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How can we distinguish fold and cycle of sedimentation on a remote sensing image or in the field?

A fold is composed of stratigraphy that is symmetric and repeated. Cyclic sediments (also called rhythmic sediments) are sequences of sedimentary rocks that are characterised by repetitive patterns of ...
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Is it possible for Mexico to have a magnitude 9 earthquake?

Everyone has heard of the Cascadia Subduction Zone and the potential threat it poses. However, I have heard nothing about The Cocos Subduction Zone, even though it caused a devastating earthquake over ...
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3 votes
1 answer
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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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3 votes
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Crustal age global map

I've been searching for a map depicting the age of each part of the crust for a long time. I'm not a geologist but I'm a physicist so I would like to know about the most up-to-date and accurate ...
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Where and how big was Sicily between 5 and 1 Ma ago?

Sicily is a geologically complex island which seems to have been extensively studied geologically and from a tectonically point of view. There are an overwhelming number of papers dealing with the ...
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3 votes
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Faster shale velocities in deviated wells

I am currently working with sonic measurements in the wells and there is an observation, that velocities are faster in shales over the deviated parts of the well. So, when the relative dip between the ...
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Puddingstone info sign for Trail Store

I run a Trail Store (sell hiking maps, swag, etc) in Mahwah, NJ, USA. I'm trying to feature a plant and rock every season. The first rock chosen is puddingstone. I created the short sign below, ...
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