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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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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How are chenier ridges and strand plains formed at wave dominated coastlines?

In the attached image, we can see chenier ridges and strand plains. How are they formed and what is the involvement of rip and longshore currents in their formation?
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What is the metamorphic field gradient useful for?

As I understand it, the metamorphic field gradient is the PT line traced out by the maximum temperature points of a series of PTt paths of rocks from the same metamorphic event. What exactly is this ...
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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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1answer
60 views

How Can We Establish Precisely What Earth's Core is Made Of?

The consensus view is that that the Earths core is composed mainly of iron alloyed with about 10 percent nickel and traces of other heavy metals, but I have seen at least one account which says it is ...
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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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38 views

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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168 views

Why would CaO be more finely spread than K2O in Granodiorite?

I recently interpreted some XRF data on samples of a granodiorite which were classified under three different types of physical characteristics: very little, mild and significant levels of weathering. ...
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Can anyone please help me identify this rock?

I was wondering if you could please help me identify this rock. It's a little bigger than a softball and very dense. Thank you in advance (https://www.facebook.com/john.beverly1/posts/...
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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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511 views

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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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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What kind of rock/mineral is this pinkish stone I found in Colorado?

I found this in my backyard and would love to know what I'm looking at. It reminds me of a fossil. I live in Colorado, Denver-metro. The sample is about 2 inches top to bottom, weighs maybe .5 lb, ...
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112 views

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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What is this 6in Nor Cal beach boulder with waxy veins?

Nor Cal beach @ low tide. 6in, photographed wet, post acid wash. Veins look waxy.
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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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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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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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1answer
54 views

Climate consequences of very large asteroids striking the Deep Ocean

For every asteroid or meteorite that hits dry land, two hit the sea. If a Manicouagan-sized asteroid struck the deep ocean (but not above a trench),how would the H2O vapour, chlorine, iodine bromine ...
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Green Rock Identification

This rock was found in the highlands of Scotland in the mountains.It is 2 1/2''x2 1/8''x 1'' it has a density of 2.95 leaves a clear streak weighs 130 grams and a hardness of 6 on Moh's scale.This ...
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310 views

Is this Black Serpentine?

I found this rock at a lake edge in Co. Sligo Ireland,its shiny black,leaves a black streak, weighs 320 grams displaces 125ml of water which gives it a density of 2.56 https://www.youtube.com/watch?v=...
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The differences on the atmospheric transportation for various trace metal in atmosphere

I have known that the atmospheric lifetimes of chemical species were highly dependent on their physicochemical properties. For example, $SO_2$ might exist for 5-8 days, while $NO_2$ could only exist ...
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why igneous phosphate rocks contain less uranium than sedimentary rocks?

Sedimentary rock phosphates contain much higher concentrations of potentially hazardous elements (As, Cd, Cr,Pb, Se and U)than igneous rock phosphates. Why? Is it because U concentration in magmatic ...
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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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python generate 3d unstructured grid

I would like to create a 3d unstructured grid based on data points with xyz and property. Can Python do this and what tools? My question is quite generic but i can provide more details: the data has ...
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66 views

Whats this stone?

Found it couple days ago and it amazes me how smooth the surface is but cant identify it please help me. Found it in north germany near a lake on a trip there.
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Can the process of subduction flatten the shape of a subducting plate relative to the plate it's going under?

There's something I’m still not quite getting about why island arcs are arcs. In the examples I’ve seen, the subducting plate is compared to a knife slicing across the surface of an orange - but it ...
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What is this dull whitish rock with ornate black patterns found in the Arkansas Crater of Diamonds?

I found this rock while wet sifting dirt brought back from the Arkansas Crater of Diamonds. It looks as if it is hand painted. It is smaller than my pinky nail. It’s dull, and makes a chalk-like mark ...
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What are the different hardness scales?

In school, I was acquainted with the Moh's hardness scale. I wondered how malleability factors into this scale and was surprised to find there are many different hardness scales: the Rockwell scale, ...
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Thermal spring. Gas and water characterization

I am interested in assessing a thermal spring in the Ecuadorian Andes. However I have no experience in these type of geological features and I am not sure how to proceed. The spring is located over ...
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How should core-rim detrital zircon ages be reported in a sedimentary provenance study?

I understand this might be drifting into the black hole of subjectivity but I would like to know if anyone knows if there is a generally accepted practice. If one has a detrital zircon with a core age ...
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volcanic effects on the climate during Pangaea

Which influence does the constellation of the continents have on the global climate? Was the biosphere more susceptible to climatic effects a volcanic eruption may cause during the Permian than it is ...
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Can zircons be analysed by the (U+Th)/He after being ablated for analysis of U-Pb?

I have zircons that have been mounted in a resin block. They have been polished to approximately half way through the zircons (as is convention) and they have been ablated to attain the U-Pb or Pb-Pb ...
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Were the results of the gravity probe B according to what was expected?

By using a gyroscope the curvature of space-time made by the earth was measured. I know that gravity is not exactly the same everywhere on the earth because of density of the mass beneath it. ...
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Rock ID: black rock found in Central Europe

I'm note sure if it's an anthracite, augite, jet (lignite) or something completely different. I don't know where exactly i found it because it's from my old rock collection. I would appreciate your ...
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Should I perform EOF analysis on an unevenly-spaced time series?

I have a dataset of sample concentrations of several ions/elements (Ca 2+, SO4 2-, K +, S, Ca, V, etc.) from an ice core which I am using to detect volcanic eruptions. The raw version of the dataset ...
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Is this a geode?

So just having issues with identification looks like a outer line of rock a bit transparent but the inside polished looks waxy other side of stone a bit more foggy but still blue visible Edit - ...
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How much hydrogen can be extracted from the deep continental crust?

Far below the earth's surface, hydrogen gas is continuously produced through serpentinization. At least some fraction of this hydrogen remains trapped in the deep continental crust; indeed, Soviet ...
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Did low $\small\sf{CO_2}$ levels affected Permo-Triassic mass extinction?

After answering this question: How did plants adapt to $\small\sf{CO_2}$ levels past 400k years? Why won't they do it again? I know Permo-Triassic mass extinction is associated to a catastrophic ...