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 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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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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What is this I found? [on hold]

I found this rock and I am wondering what is it. Could you please let me know.
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1answer
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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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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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What kind of rocks are these light-colored ones with shiny metallic inclusions? [closed]

My dad found these rocks in his garden. They have some shiny metallic looking pieces in them. Would anyone be able to identify what they are? We live in South Africa if that helps. Thanks!
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1answer
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I found this stone with metal linings can someone identify it?

I am more curious about the metal on the surface (if it's even metal?) on this stone :) I don't really remember where I found it, probably at this beach of the Baltic Sea, but there is also a chance ...
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1answer
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What kind of stone is this? [closed]

Years ago, I bought from a flea market two strange looking stones, that the owner said he had found under the sand of a dune in the desert (I don’t remember which). Maybe it’s true, maybe not, but I ...
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1answer
145 views

Mineral Identification [closed]

I have a green, moderately magnetic, rock with yellow inclusions. The rock is very heavy for its size. What is the most likely minerals in such a rock? Update: Found on the Maine coast. Rock has been ...
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1answer
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Found a light brown rock with concentric circles on it. Is it a fossil? [closed]

I found the rock in the picture while visiting Pawnee National Grassland (Colorado, USA). The rock shows concentric circles on both sides. On one side these circles are very clear, on the other side ...
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Do earthquakes produce folds on rocks?

Earth rocks are frequently folded at surface. Folds in alternating layers of limestone and chert in Crete, Greece. Source: commons.wikimedia Are earthquakes the main mechanism ...
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4answers
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What is this Lake Michigan rock?

Rock found along northern Lake Michigan, (Charlevoix, MI). Made up of very thin crystalline layers. There are small, round bubble like bumps that protrude from the surface. Doesn't show well in the ...
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1answer
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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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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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1answer
329 views

What are the differences in terms of appearance between sandstone and limestone?

On the field, I find it very difficult to differentiate the two types of rocks just by looking at them.I know that you should do some analysis of the sample before any conclusions. But, for example in ...
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Are sand deserts the greatest natural convection heaters on Earth?

Ask any climate scientist the question: "Why are deserts so hot in the day time and so cold at night" and generally you will get the same answer, it’s all about the lack of moisture and latent heat ...
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1answer
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Is there limestone under the Oregon Coast Range?

I've found some diagrams of the Oregon Coast Range, but they are very basic. An friend said he thinks there is limestone deep underground, but my understanding of the formation of these mountains is ...
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1answer
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Help identify my redbrown rock with crystal like formation on the inside

This rock is red/orange/brown in color. It is slightly clear/translucent when held up to light. Will not scratch with a knife. Has a crystal like structure on the inside.
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Help to identify unusual rock please! [closed]

Can someone please help to identify this rock? We are hoping it's a meteorite! About 3 x 2 inches, seems heavy for its size and very hard. Brownish/grey on the outside and smooth. It has a rust ...
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1answer
107 views

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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1answer
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Is there a name for subduction boundaries at the North of Australia?

I know the ridge at the South of Australia is named Southeast Indian Ridge. I would like to know if there is a geological name for the three subduction branches that cross indonesian zone, at the ...
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1answer
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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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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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3answers
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Pinkish rock with red 'veins'

I found this rock in Smithfield NC. It does scratch glass. A butter knife didn’t scratch it. When you hold it to a light it has an orange glow. It didn’t leave anything on porcelain.
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Is this olivine? [on hold]

Could this small rock be olivine? It has got a rough feeling surface, and 'it's heavy. I found this in Wales 12 years ago.
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1answer
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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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How older is this snail shell possible could be?

Last weekend I was in Xınalıq(the village in Azerbaijan) and found this snail shell. I am wondering how old is this?
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3answers
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Rock ID: Found on South Downs in East Sussex UK

I found this slightly rude-shaped rock/stone on the South Downs in East Sussex, UK years ago. It was embedded in a chalky path and came out in the two pieces in the photo. It is heavy for its size (...
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What is this blue rock?

I am trying to identify a rock my husband found.The rock was found in Columbus Ohio about 20 feet (6 m) down. It is about the size of a basketball and extremely heavy (90 lbs) and difficult to cut ...
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1answer
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What is the difference between subvolcanic rocks and plutonic rocks?

I'm studying Plutonic (Intrusive) rocks and I really don't understand the difference between Plutonic Rocks that form in Sills and Dikes from the so called subvolcanic rocks, also known as a ...
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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
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How is the difference in crust and mantle composition explained?

We know that the composition of the crust is SiAl and SiMa and the one of mantle is mostly ophiolites, but why? Which are the geological processes that make this difference exist?
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What is this white rock with black speckles throughout?

I was wondering if you have any ideas on what kind of rock this might be? I know that it doesn't effervesce with HCl (no reaction with hydrochloric acid at all) and the size and shape of each grain is ...
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If rocks are stones, what type of rock are gallstones? [closed]

From Wikipedia: Rock or stone is a natural substance, a solid aggregate of one or more minerals or mineraloids. For example, granite, a common rock, is a combination of the minerals quartz, ...
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What type of ore is this? [closed]

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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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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Could the Grand Canyon be flooded by the ocean if it got deep enough?

The Colorado River has been carving the Grand Canyon for a few million years now, such that the canyon floor is around 6000 feet lower in elevation than the surrounding area, at about 2400 feet above ...
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1answer
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Is this rock Massive Epidote?

enter image description here This is a close up of outside of chipped off piece, and inside alsoI found this rock in Co. Donegal Ireland on a river bank buired under the dirt. It weighs 16.4lbs- 7....
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What's the difference between a crater and a vent? [closed]

Crater is above a vent whereas a vent is below it. All the best....
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1answer
78 views

Peninsula vs Cape [closed]

I know that Peninsula is much larger than a cape, but is there a definite way to differentiate them? I.e. by area- if the total area is larger than 30 sqkm, any headland is classified as peninsula..
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Cause for round holes in stones

I picked up this stone form a beach on the south coast of England (lancing). How is it possible it has such round holes? Plenty of stones looked similar.
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At what depth does the underground begin to warm up?

Spring water comes out colder from being underground. But if you get deeper the temperature goes up. At what depth does the underground stop getting colder and begins getting warmer? Is there a map ...
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1answer
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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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1answer
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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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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? [closed]

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? [on hold]

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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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 [closed]

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 [closed]

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 ...