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thank you for your interest in the article. I'm the lead author on this paper (Shipway) and I happened to come across your post when looking through all the media stories on this animal. To answer your question; yes, you're right, the rock is a calcareous sandstone. It was easy to split, partly because it is a naturally soft rock and partly because the ...


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There is a paper about this in the Bulletin of Volcanology (Hetényi et al. 2012). Cooling rate seems to be the main parameter controlling column size (faster cooling yielding to thinner columns). According to the authors, cooling rate is itself controlled by two non-independent factors: (1) the geometry of the lava body, and (2) the chemical composition of ...


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Limestones are usually categorized following the Dunham & Folk classification. Only very rare or special limestones were given a name and these are often named after the location where they can be found e.g. Travertine. The images you provided are not very explicit which makes it literally impossible to clearly identify the limestone. Please consider ...


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The rivers transport most of the sediments to the coastal or marine basins where they accumulate. An exception are lacustrine basins, but most of world rivers sediments are deposited on shallow or deep marine basins. When the stack of sediments is large, listric faults develop, and the bottom layer get pushed down into the earth. This process is called ...


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Yes, there are many differences and subdifferences and nuances. I will try to keep it in simple terms which will satisfy your question. Alkaline magmas form by low degree partial melting of the deep mantle. This is why you see them in hotspots. It's very hot down there, but you do not form a lot of melt. For example, the amounts of melts in Hawaii are ...


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Why don't pyroxenites and peridotites appear on this diagram? Because they do not have any quartz, feldspars, or felspathoids. The same Wikipedia page also says this: QAPF diagrams are also not used if mafic minerals make up more than 90% of the rock composition (for example: peridotites and pyroxenites). Instead, we use a different diagram, that has ...


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So, the question is how can I tell if a minedat description of a plutonic rock is favorable according to the criteria of the quoted passage? No. The description doesn't say how much feldspar is in the rock. It could be 5%, or it could be 20%. It also doesn't say anything about the iron content of the feldspar (although with some petrological hand waving you ...


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Diabase is indeed relatively erosion resistant. One of the reasons is grain size. Consider the two other chemical equivalent of diabase: gabbro (coarse-grained) and basalt (glassy and fine-grained), which should potentially be similarly erosion resistant. This is not the case. Both gabbro and basalt erode very easily. Coarse-grained rocks, in general, ...


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I do agree with Gimelist how gold is accumulated through hydrothermal fluids, adding that the main driver is for this process is volcanism. There is, however, something interesting to be noted. We can find very 'old' gold of the Archean, more than 2 billion years ago, and mainly during 2 periods of the Archean, mainly hydrothermal gold in very old ...


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I believe the author's was referring to phenomena like salt diapirs (where mobile salt deposits intrude into heavier overlying sediments). These produce low hills in the gulf coast region of the United States. The salt that is moving is not liquid, it is merely mobile. I do not believe the author of the book you reference was referring to sand and mud ...


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Molten rock must be a liquid, mobile rock is any rock capable of moving, sand and mud can be mobile.


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No, sediments do not sink into the earth because they are too light. They stay on the surface and over very long times they form the continents. But they can get buried under many km of other sediments as parts of the crust they're on subsides or is pushed over other parts. Thus they can get into pressure/temperatue conditions where diagenesis (see other ...


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In your question I think you are mixing up metamorphic conditions such as the conditions that gneiss forms from sedimentary rock with the formation of diapirs. Diapirs occur where a less dense layer of a relatively plastic rock has denser overlying formations create sufficient pressure so that the less dense substance deforms and rises over time. Diapirs ...


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The rocks are undoubtedly of volcanic origin, and I would attribute the marks on their surfaces to shrinkage while their interiors were still in a semi-molten condition but rapidly cooling. The white crystals are probably quartz.


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This is an excellent question. What does happen when you drop a crystal of olivine into liquid rhyolite? There are several answers which all depend on the exact composition of the olivine, how much magnesium is in the rhyolite, temperature, size of the olivine, how much olivine are you dropping into how much rhyolite, and more. Let's take the most extreme ...


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Radial fracture is fairly common. It can form from cooling, drying mud, chemical shrinkage, impact, or several other means. Since you are looking at volcanics you are probably looking at cooling shrinkage, The interior cools slower which means it shrinks more and that's how your get radial fractures. Fractures form perpendicular to whatever the cooling ...


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The first department that comes to mind is obviously academia, i.e. faculty or research positions at universities. However, there are many other career paths available (hopefully: there are not enough academic positions for every student completing a Ph.D...). For volcanologists, there is actually a nice site called volcanologists outside academia. As the ...


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