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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42 views

Are these igneous Liesegang rings on a popular Oahu, Hawaii hike?

I hiked the Lanikai Pillbox trail (Oahu, HI). I noticed eroded concentric rings in the igneous rock with a hard center. I'm unable to find the geologic cause of these rings. Are they Liesegang rings? ...
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Term for the Process of the Early Earth's Crust's Changing Mineral Composition

In the book, Story of Earth-The First 4.5 Billion Years, From Stardust to Living Planet, by Robert Hazen, Chapter 3: He discusses the changing mineral composition of the early Earth's crust from ...
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Can you please identify the type of rock and whether is it natural or man-made? [closed]

I found this rock in my garden (Cheshire,UK) and wondered what type of stone it is. The two largest holes on either side go right through, almost like a bead and I wondered whether this had happened ...
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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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How much earth has to be moved to get one tonne of copper

I am trying to make sense of the mining process of minerals or metals. I found two measures related to waste: the stripping ratio (which is usually larger than 3:1 for copper, i.e. 3 tonnes of waste ...
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Differentiate correlation of between depth and bouguer anomaly

Assume we measure bouguer anomaly (g) and depth (H) of the certain horizon through a profile at each point. Based on data we get a correlation between H and g and express it with a polynomial equation ...
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Using IOS DATA unsupervised classification in Envi, how do you ensure the algorithm correctly classifies between water and dense vegetation?

I have performed an IOS DATA unsupervised classification algorithm to a Landsat scene in Envi software. Bands available are: B, G, R, NIF, SWIR plus spectral indices NDVI and NDWI. Keeping the inputs ...
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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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Ore prospecting and the low-hanging fruit effect

I'm trying to acquire an understanding of how the difficulty of prospecting for useful ore has increased over historical timescales. Intuitively, I would expect that centuries or millennia ago, you ...
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How to add scale in DSLR plus microscope set up by default?

We have an Axioscope microscope and planning to install a Nikon D5300 camera on top of it. The software I looked up, is DigiCam Control. The downside is we cannot add scale by default. The scale has ...
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Permeability test

What are the different ways permeability of a core specimen can be determined accurately for fluids with different viscosities and their mixtures?
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How ocean pockmarks are formed and how quickly?

I couldn't find much information about it on google and I don't know much about how pockmarks work.
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Ore Deposit Identification

What type of ore deposit does this rock best represent? A rock with a porphyritic texture is cross cut by a stockwork of quartz veins. Bordering the veins is extensive alteration of the host rock. ...
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What is this long mark undersea

Visiting Google Maps, I came across this long, sinuous, while pretty regular mark undersea that looks like an ancient river, when the sea was way lower, or a big (big!) boulder that could have rolled ...
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Feldspar content of coarse-grained igneous rocks

From the chart, I would say that plagioclase feldspar is more abundant in coarse-grained igneous rocks than alkali feldspar, as it is found in all three listed, whereas alkali feldspar is only present ...
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Quartz mineral category

Different learning resources categorise quartz differently. Strictly speaking, is quartz a silicate mineral or an oxide mineral?
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Coarse grains in a sample of Rhyolite suggest that it formed by

Coarse grains in a sample of Rhyolite suggest that it formed by …… A-rapid cooling of molten rock materials at the Earth’s surface. B-slow cooling of molten rock materials at the Earth’s surface. C-...
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Cleavage of minerals

What is the difference between 3-dimensional cleavage and cubic cleavage? I think, they are the same, but I am not sure about if I was right or not.
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puzzling statement on earth history!

A Geology proffessor recently told me that around 200,000 years ago, when homo sapiens emerged, that "...all of civilisation can now fit on the width of a single strand of human hair." I am ...
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Arabian Desert rock formation

I'm interested about this rock formation in Arabian desert. The rock looks like melting chocolate. Not sure where the exact Location, the source says it around Al-Ula, Saudi Arabia. Here the image ...
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How do geologists measure green house gass emmissions from large regions

I read here that volcanoes release about "0.6 billion metric tons of carbon dioxide per year". I wonder though, how scientists can estimate the emissions from large regions with geological ...
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Hydrocarbon resources extension. How?

Pardon my naive question. But I heard this argument quite sometimes. One can find at the Schlumberger careers page the particularly interesting FAQ: “We are often told that oil is running out. Why ...
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How do long, thin, island chains such as North Carolina's outer banks, form?

I can't think of a possible explanation, there's no volcanic activity in the area, and it gets destroyed every time a hurricane passes through. How did it get there?
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Stratigraphy of limestone applied to the Great Pyramid of Giza

The Great Pyramid of Giza is made from blocks of limestone quarried from the Giza plateau. The pyramid is composed up of about 200 layers, with individual blocks varying in thickness from 20 to 60 ...
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How to read stratigraphy data?

I have a list of geological data. The data is for 3 variables: member, level and L+/- These variables correspond to a particular position on a stratigraphic column/chart. I would like help with ...
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How can the 'crystal cleavage' of apatite have a four-digit number?

On Wikipedia's page for apatite, the crystal cleavage is listed as [0001] or [0101], which I assume are Miller indices.... But how can there be four numbers/digits instead of two, like there usually ...
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How do you infer what a cross section might look like below sea level?

Here is a schematic of a cross section which should represent an anticline: https://postimg.cc/4HcmmZ26 Below sea level, I have inferred what the units might look like with the dashed lines. As I have ...
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What is the best way to split strike and dip data on the image provided into “domains” in order to interpret folding on a stereonet?

Link to the original image: https://postimg.cc/v4bRqxxR I believe this image represents two folds which are overturned and plunging. I would like to analyse these folds on a stereonet, but I am unsure ...
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Why is Earth's density gradient a step-function, rather than smooth?

Why is the density of particles in Earth's atmosphere above surface-level so much less than ground and below? Why, instead, isn't Earth simply a ball of swirling gasses / liquids, which become ...
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Are metals and other elements in every continent?

I originally thought that you can only find certain things like iron, copper, and other things in certain places in the world and deep in mines but I saw in a few YouTube videos that you can find iron ...
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Are Fluvial and River Terraces the same?

I study about fluvial terraces. However, resources related to this topic are limited. When I searched fluvial terraces in geomorphology books, I cannot find anything, but I find river terraces. My ...
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What happens when a mid-ocean ridge sub-ducts underneath continental crust?

I'm aware that oceanic crust always sub-ducts to continental crust, but surely the geologic forces pushing the ridge apart in the first place isn't just going to turn off, right? Any answers would be ...
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Question Concerning Meteorite Ejecta Travel

I was researching more into the studies done by Kjaer and his team ( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6235527/ ) concerning the hypothesis about the Younger Dryas impact crater named ...
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Identifying thrust faults on a geologic map

I am not able to upload the map as the file is too large, but I have a map which states there is an over thrust fault. It has two ticks on it indicating downthrow to the NE. The downthrow is pointing ...
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Is it a Lake, Cove, Tidal Creek or a Spring?

We are very confused by this water body. This is called "Carolina Lake" however other suggests that it is not a Lake but a cove. Other say it is a tidal creek for it is influenced by tide. ...
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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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Structural geology

Map 4 shows two dykes that have been offset by a vertical fault. In different coloured pencils, draw strike lines on each dyke. (a) On a blank sheet of paper, use the strike lines that you have drawn ...
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Will the sea get saltier forever?

The sea wasn't always salty. It's been getting saltier over millions of years as minerals dissolve. Is there a natural limit to this process, or the will the sea keep getting saltier forever? Is there ...
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How are tall cays formed?

From reading about Cays on Wikipedia it seems they are formed from coral reefs covered with sand or gravel. There are however some cays scattered around the world which are hundreds of feet off of ...
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SC7 and SC10 Lithology Classifications

I am looking for the full names of the lithology classifications SC7 and SC10. According to the FAO's guidelines for soil description SC3 e.g. refers to silt-, mud-, claystone. What do SC7 and SC10 ...
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Does science suggest Venus would resume plate tectonics if surface water were somehow reintroduced and rotation sped up? [closed]

Assume that we're talking about a terraformed Venus with an Earth-like atmosphere so no risk of the water simply boiling away before being allowed to permeate the lithosphere. Does this meet the ...
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How did Mount Evans become a mountain?

Multiple websites state that the mountain, which is in Colorado, was formed by an intrusion of magma about 1.4 billion years ago, forming a batholith. On the other hand, the rocky mountains are said ...
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What is this red glassy rock [closed]

I found rocks looking like this in my backyard but cant get to know what they are or how to find out. Below are pictures I don’t know if there’s more info I should mention. If there’s anything please ...
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How many years does it take for rivers to form?

I've looked this up as best as I could and couldn't find a clear answer. I've seen for example articles on the age of several rivers as being the oldest ones, but nothing regarding the opposite. Could ...
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How are Quaternary alluvial deposits differentiated in subglacial latitudes?

The USGS maps of coastal California label alluvial deposits as Qyf and Qof — the “younger” and “older” fans of coarse sediments. But in areas of the earth that never saw Quaternary glaciation (like ...
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Why REE concentration in a melt due to fractional melting is less than in a melt of same source rock due to batch melting?

I plotted this ree data for batch melting and fractional melting for the same source. From the plot we can see that the melt due to fractional melting is more depleted in REE than the melt due to ...
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Will California become a subduction zone in the distant future

California is one of the few places in the world that lie on a transform fault. My question is why considering the fact that North American Plate is moving westward shouldn't California be a ...
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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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What formed this rock slide formation near Hyndman Peak Idaho (photos)?

While hiking Hyndman Peak in Idaho a couple weeks ago we noticed a rock slide that appeared to be formed by a glacier, however it was on the west side of the mountain. It was also strange that the ...
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How much role does radioactivity play in making Earth geologically active [duplicate]

A hot molten core is important for making the Earth geologically active. I believe most of the heat is from the time of the planet formation, and the high pressures due to everything pushing down to ...

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