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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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I found this small round heavy rock in a box of my dad’s old army stuff

Heavy black silvery Rock found in s box of my dad’s old army stuff. He was stationed in Arizona sometime in the 50’s. Not sure if it’s from there or just happened to be in that box. (https://i.stack....
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Why can't we dig deeper?

I recently read on another SE site that there's a limitation on how deep we can dig into the earth. A Google search reveals that temperature is the problem. I quote from a Popular Mechanics article ...
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Help identify my rock please? [on hold]

found this in the backyard, any ideas which type it is?
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1answer
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I found this rock on my way home and have done some research and only found one picture that relates to this rock, WHAT IS IT?

I have found this strange rock on my way home it piqued my interest so I picked it up did some research and found little to nothing. Might be related to shale not sure though. What is this strange ...
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Is this Mutton Fat Jade?

Found this near the Shannon River close to Carrick on Shannon Irelandenter image description here Could this be Mutton Fat Nephrite Jade? Thank you
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2answers
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Can anyone help me identify this type of translucent green mineral? [closed]

This is the photo of the rock. I found it in the mountains in yemen, near rocks where a well was dug out. Its translucent green and It doesn't feel that heavy. I think it's some type of quartz.
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Can someone help ID this rock

Found today in a creek in Indiana, has a geode look and the broken edge shows red opaque facades.
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1answer
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UK Mineral identification help

Can anyone help me identify these minerals please? I found them on a beach in northern England. The first has tiny angular crystals, some slightly pinkish maybe in certain lighting conditions but grey ...
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Can you please help me to identify this thing I found inside a rock in the Almanzora riverbed Spain

Can someone please help me identify this thing I found inside a rock in the Almanzora riverbed Spain
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What is this heavy green rock?

I found this grenish rock at a beach in Northwest Ireland called Inishcrone. It measures 45mmx35mmx22mm. It weighs 57 grams and has a density of 2.90. It is opaque, does not attract a magnet. It ...
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Is there a widely accepted reason for the formation of tafoni?

Expansion of tafoni seems to be based on weathering (seems reasonable enough.) But what creates them in the first place? There are a number of explanations online (Wikipedia lists eight plausible ...
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What is an inversion

What is an inversion? What happens to the sediment in between? I understand that as the crusts move together a bulging appears.
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Why does gold and other metals conglomerate

When gold, or some other metals, such as copper, are found, they are often found in large nuggets. But, from what I understand, gold is produced in quite stochastic stellar processes. As such, shouldn'...
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Is sterescope still used to do cartography with orthophotography?

I used this tool at my degree a couple of lusters ago to do cartography with aerial orthophotos. We used it on cartography and geomorphology subjets. Source: gumtree.com The method consists ...
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what type of rock is this? blue/green and brown [closed]

I found this rock while up in the mountains and I have no idea what type of rock it is.
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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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What are these rocks? [closed]

I found both of these in a river in North Yorkshire. Can anyone suggest what they may be? Thanks
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Assessing graded bedding in metamorphosed pelitic sediments

I have the following image of metasedimentary outcrop from a Proterozoic continental rift-fill sequence: The middle layer has a pelitic composition and contains abundant cordierite porphyroblasts (...
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What type of ore is this?

I have found this metal somewhere in a semi-desert area in Ethiopia. The place has no mountains and has no human contact yet. It is magnetic and has some rust on the top which can be removed using ...
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1answer
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What is this heavy, dark grey and almost round rock?

I found this 'rock' on the beach in North West Washington State. It's almost perfectly round save for a few bumps, it's dark grey in colour, solid, feels smooth like any stone you'd find on the beach,...
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What is the average color of dirt?

Where I live the soil is red. Is there a map or chart where you can see the average color of the dirt according to geographical location? What would the color be if all of the dirt on Earth was ...
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2answers
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What are these metallic nodules that were found at low tide on the UK south coast?

Smooth spherical crystalline metal nodules Outside and inside surface does not scratch with a knife blade Inside lustre brassy, radially striated metallic crystals radiating from a lumpy centre at the ...
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1answer
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Metallic rock identification from Ontario Canada

This rock was found in Lake/Lac Clair near Sturgeon Falls Ontario Canada in about 2 feet of water next to the edge of the lake. It can easily fit in my hand. You can see a size comparison in the ...
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1answer
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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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Is Iceland an example of a hot-spot overlying a mantle plume?

Iceland has been cited as the location of a hot-spot overlying a mantle plume (similar to that of the Hawaii chain in the Pacific), though for some time this model has been challenged (see Gillian ...
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Why is the temperature between the earth core and surface not distributed linearly?

So I read somewhere that the inner core temperature of Earth might be as high as 7000 °C. Depending on the composition of the different layers towards the surface, the temperature should decline ...
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1answer
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What are the causes of the supercontinent cycle?

Throughout geologic history, Earth's continents have broken apart and come together to form supercontinents multiple times, in a somewhat regular period, known as the supercontinent cycle. The length ...
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How long until Earth's core solidifies?

How much longer does Earth have until the core turns solid? Does global warming change these estimates at all?
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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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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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How old is the Earth?

According to most articles I've read online, the estimated age of Earth is 4.5 billion years. Question: How old is the Earth? So I actually want to confirm that this is the case. Maybe there are ...
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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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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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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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What leads to formation of a nonassociative gas reservoir?

Why in some cases natural gas occurs in association with oil (associated gas) and in others there is no oil (nonassociated gas)? Is it because of the type of the rock? Or is it the pressure/...
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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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Is there a reason most mountain ranges seem to run parallel to coastlines?

Eyeballing a map of the world, it seems that most mountain ranges that don't occur along continental fault lines run parallel to coastlines. Is there a reason for this?
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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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Why does sea level correspond to boundary between oceanic and continental crust?

Is it a coincidence? the first is determined by the amount of water on the Earth and the second comes from evolution of tectonic plates. Still, oceans seem to fill exactly the oceanic crust.
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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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Identification required, rock formation found whilst on holiday in Cephalonia, Greece white object embedded inside?

This rock was found in kephalonia Greece, on a beach in lassi. The rock is black in colour, smooth with thumb like prints, very metallic smell and very slightly magnetic. We took this rock to oxford ...
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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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To what accuracy and precision do we know the volume of the Earth?

Satellites such as GOCE and GRACE measure the geoid with unprecedented accuracy. Altimeters can determine local surface elevation with millimetre-precision. This makes me wonder: to what precision ...
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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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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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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
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Which ocean is going to be swallowed by the Supercontinent Cycle, Atlantic or Pacific?

The register shows several supercontinents have been formed on Earth's History: "The most recent supercontinent, Pangaea, formed about 300 million years ago (0.3 Ga). There are two different ...
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Is it true that earthquakes are not felt in a cave?

I took a tour of a cave in northern California last weekend. The tour guide asked us, "If an earthquake occurred, what would we feel in here?" My answer was, "fear," but she said we would feel ...
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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 ...