20

The basic differences are: Geology study of rocks and minerals: the study of the structure of the Earth or another planet, especially its rocks, soil, and minerals, and its history and origins structure of area: the rocks, minerals, and physical structure of a specific area Petrology study of rocks: the study of sedimentary, igneous, and metamorphic ...


18

I'd like to add to Brian's answer, and also point out some inaccuracies. First of all, it is not true that felsic minerals have lower melting temperatures than mafic minerals. Here are some melting temperatures of common minerals, sorted from high to low: Forsterite (mafic): 1890 °C Quartz (felsic): 1713 °C Anorthite (felsic): 1553 °C Diopside (mafic): 1391 ...


18

Good question! As you know, Bowen's reaction series describes the order of crystallization of silicate minerals in a cooling magma. The complex anion of silicates is a tetrahedron of four oxygen atoms surrounding one silicon atom, connected with strong covalent bonds. Each tetrahedron may be isolated from one another or they may be bonded together ...


18

It's an interesting question, but in practice I think it's impossible to answer. It's very difficult to measure the rates of many of those processes, and the divisions between rock types can be quite ill-defined (for example, in migmatites). There's no scientific instrument we can point at a chunk of the earth which will tell us "in this region, 29.4 ...


18

I'll take the form of the question given by another person here and attempt to provide a different answer. So what you are asking is: "How did gold become so concentrated in certain parts of the world?" So yes, gold is all around but the concentration is too low to make extraction of it worthwhile. You need some process to take small amounts of gold from a ...


16

There is a technique called "Exposure Dating". Using e.g. cosmogenic nuclides (they are produced in the first metre or so of the surface of a rock which is exposed to cosmic rays, i.e. on the surface of the earth), it is possible to estimate the amount of time that the rock was exposed. With some assumptions, you can get an exposure age of the fracture ...


15

I'm quoting from my old The Penguin Dictionary of Geology by D. G. A Whitten & J. R. V. Brooks, published in 1979. Rock (1) To the geologist any mass of mineral matter, whether consolidated or not, which forms part of the Earth's crust ... (2) The civil engineer regards rock as something hard, consolidated, and/or load bearing, which, where ...


15

Here, you can use this shoddily drawn table.


15

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 ...


12

One can only speculate based upon a photograph - however they look very much like mineralized fractures. At some time in the past this rock mass may have fractured in response to thermal or tectonic stresses. Fluid may have then penetrated relatively long distances along the fractures into the area and infiltrated shorter distances into the wall rock along ...


12

"Basalt" per definition is a fine grained rock (that is, you can't see the individual crystals with the naked eye, aka aphanitic) with a certain chemical composition. The coarse grained form of this rock is called a "gabbro". A diabase (or dolerite) is something in between, but let's ignore it for the meanwhile for the sake of simplicity. So quoting from ...


12

I usually tend to think that the shorter a definition is the more it introduces ambiguity and errors. So I would just think about your audience and choose an appropriate length (You didn't mention the level you are teaching for). Similar to the definition of life you can offer to your audience characteristics, which some rocks will conform more or less. ...


11

Most sources say that rocks are made of stones. (Or at least that stones are rock fragments.) From the Bing dictionary (definition of stone): hard nonmetallic material: the hard solid nonmetallic substance that rocks are made of. rock fragment: a small piece of rock of any shape shaped rock fragment: a piece of rock that has been shaped for ...


11

Why you should not do it The QAPF and related diagrams are intended for classification of rocks in the field, or preliminary classification with modal proportions as seen in the optical microscope. They are not designed with the chemical composition of the rocks in the mind. Furthermore, these diagrams are merely descriptive and not genetic. They do not ...


11

The best way to learn about rock types is to handle rock specimens guided by an experienced geologist. By handling rock specimens you get to feel the weight of the rock, its roughness or smoothness or if it feels slippery, soapy, glassy, firm or crumbly. Is it weak or strong? You will also be able to better see the colours in the rock, the sizes of the ...


10

Not as far as I am aware. Any dating of the rock would determine the formation age of the rock (dating isn't quite as straight forward as that, and there is a whole science behind what each dating technique actually determines but for simplicity's sake we say it is the formation date) but the fracture plane,where the hand sample has broken away from the ...


10

You are correct about halite and sylvite. I might add that carnallite also has an extremely bitter taste. These three minerals are chlorides and dissolve very easily, so that may be a part of the issue here. Differentiating mudstone (clay) from siltstone is actually not about taste, but rather about texture. Note that this can be misleading. If you have a ...


10

Nuclear wastes should be stored in containers designed to contain and isolate radioactive material from the environment. One possibility for the storage of these containers would then be to place them in a repository located in a tectonically stable, dry, geological formation. As far as lithological characteristics are concerned, it would be best to locate ...


9

First, a short introduction to incompatible elements The Earth's mantle is mostly composed of the minerals olivine, pyroxene, anorthite, spinel and garnet. These minerals are made from the elements Si, Al, Fe, Mg and Ca. In the figure below I've put them in the MRFE field (Mantle Rock Forming Elements). The trace elements, the elements that occur in very ...


8

First of all, your statement implies that volcanism didn't occur in Troodos. That is not true. Troodos was even referred to as "Troodos Volcano" once in Miyashiro's 1973 article about Troodos. A geological map of Cyprus clearly shows that a large portion of the ophiolite is composed of lavas (volcanic) and dykes (sub-volcanic): (source) Note the red, ...


8

After some brief research, serpentinite diapirism occurs due to deep penetration of seawater at temperature around 100-200$^o$C [1]. To the south of the rift that was forming the ophiolite sequence there was an oceanic plate subducting as African plate moved north. This subducting oceanic plate provided the seawater that serpentinized the harzburgite in the ...


7

Geology/Petrology has proposed some models for the origin of basalts which are based upon chemical evidence from rocks. Modern origin-models have been constrained by isotopic chemistry for some time. I do not claim to be current in this subject, but I believe the conclusions in this classic paper are still accepted as the most likely origin models. Models ...


7

According to the image that you provided, what you are seeing are not spherulites, but rather epoxy bubbles. More on that later. I will first answer what are spherulites: Spherical features observed in thin sections can form by several ways. Devitrification - this is the recrystallisation of glass. I think it is more common in rhyolitic rocks than in ...


7

The answer depends a lot on what you mean by "excluding shale oil". Tight oil production, commonly referred to as "shale oil" is about 4 million barrels per day currently (2014), compare to almost none in 2005. Canadian oil sands production is at 2 millon barrels per day, compare to about 700,000 per day in 2005. So compare to 2005, tight oil (shale oil)...


7

What you are looking for is information about the "Oslofeltet" (Oslo-field) in Norway (dated to be from the Ordovicium period, 443 - 488 million years old). This is a concentrated field of of fossils. There is a Sement museum ('cement') in a small place called Slemmestad where it is possible to view fossils from what was formerly an ocean bed. Geologicaly ...


7

Clastic sedimentary rocks are classified by size of the sediment particles making up the rock. Particle size descriptions like sand, silt, and clay have specific meaning in geology and engineering. (see chart below). Shales, mudstones and claystones are rock types that are very similar to each other. Siltstone - greater than half of the composition is ...


7

The formation of quartz veins needs fluids enriched in Si. Usually Si dissolves somewhere in neighbouring formations, gets transported by fluids and precipitates where the fluid pressure is low (the fluids Si-saturation capacity decreases with decreasing fluid pressure). Fluid pressure is usually involved in rock fracturing. When it builts-up, it can ...


7

The transformation of sand into sandstone per se cannot be directly witnessed, as it's happening deep in the earth. However, there are types of cementation that happen quickly and in plain view: A ScienceDirect article on Cementation says: Cementation is the precipitation of a binding material around grains, thereby filling the pores of a sediment. Berner (...


6

Under the assumption that we don't know anything about sampling, preparation and analysis we have to proceed with caution. Any of these steps can introduce effects that can produce stronger signals than the natural geochemistry of a rock sample. Just to give you an idea of the errors: Sampling a heterogeneous rock can produce very different whole rock ...


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