What is Formation: Definition and 506 Discussions

A geological formation, or formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguish it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers.A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock.The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by Abraham Gottlob Werner in his theory of the origin of the Earth, which was developed over the period from 1774 to his death in 1817. The concept became increasingly formalized over time and is now codified in such works as the North American Stratigraphic Code and its counterparts in other regions.Geologic maps showing where various formations are exposed at the surface are fundamental to such fields as structural geology, allowing geologists to infer the tectonic history of a region or predict likely locations for buried mineral resources.

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  1. tellmesomething

    Why Does Surface Tension Allow Bubbles to Form Despite External Pressure?

    The solution manual says that before water enters the hollow So here an air bubble of radius R will escape from the sphere. The excess of pressure inside the bubble is 2T/R. The excess of pressure prevents the penetration of water into the sphere. Water begins to penetrate when the excess of...
  2. DavidCummings

    I Did James Webb cast serious doubt on the Big Bang?

    If you read articles like The James Webb Space Telescope prompts a rethink of how galaxies form you see that recent images of early galaxies have thrown some doubt on theories of how galaxies have formed and when they started forming. But if you read about the JWST in the popular media -- and...
  3. C

    B Atom energy band formation and electron allotment

    This is actually a two-part question: 1) According to the Copenhagen Interpretation, atoms have energy bands but there's no explanation of how these bands are derived, or why they only form for protons/antiprotons. Any thoughts? 2) The Copenhagen Interpretation mentions that when an atom's...
  4. haushofer

    I Formation of jets with accretion disks at black holes

    Dear all, I'm going to give a course about black holes at an astrophysics association. The public will consist mainly of lay persons, perhaps wit a little bit of physics background. My background in General Relativity is good, but my background in astrophysics at bit less. My question is if you...
  5. F

    B Formation of Brown Dwarfs in filaments?

    Hello, I'm in grade 12, writing a term paper on brown dwarfs and am currently looking at their formation. I have now come across the formation of brown dwarfs in so-called "filaments" (link to the page below), but can't find out anything about them, except for the fact that they are filamentary...
  6. anorlunda

    I JWST Image Reveals Processes Ejecting Material in Star Formation

    Thanks to the JWST, we have this stunning picture. The APOD description says What are the processes that eject material at this stage?
  7. S

    I Is energy conserved during the formation of local systems?

    I found an old article (https://journals.aps.org/pr/abstract/10.1103/PhysRev.137.B1379) which talks about conservation of energy in an expanding space. Apparently, the author found that energy is conserved at local scales (like the motion of planets in our solar system) as one would expect, but...
  8. BWV

    I Help me on the timeline of star formation in the early Universe

    Referencing this posted on the Webb thread: https://www.quantamagazine.org/two-weeks-in-the-webb-space-telescope-is-reshaping-astronomy-20220725/ So will they able to do spectroscopy on GLASS-z13, the galaxy dating 300M after the big bang? Do they expect to see any heavier elements in a galaxy...
  9. jaumzaum

    I Why does hot air have low pressure? (wind formation)

    I was studying wind formation from the continent to the sea during day (direct circulation) and the explanation I found in almost all the textbooks was that: 1. In the continent during day the ground becomes hotter 2. The particles in the air increases their temperatures due to induction 3. When...
  10. samy4408

    Lipid Formation: Fatty Acids, Glycerol, and Sphingosine

    Hello , I am studying lipids and a point got me confused . it is said that beside the fatty acid we have glycerol and sphingosine that forms the backbone of the lipid . is the lipid formed by those 3 components at the same time (fatty acid +glycerol +sphingosine ) or it is formed by the fatty...
  11. Astronuc

    Formation and evolution of the Great Lakes in US/Canada border

    I was watching a program on the formation of the Great Lakes, and it is quite interesting and fascinating. The huge salt deposits under the Lakes Michigan, Huron and Erie and fossilized sea sponges provide evidence of a salt water sea in the past. Limestone formed from successive corral reefs...
  12. S

    I In what formation does this simple block universe exist?

    This is just a rough estimate of what a simple bock universe might be to an observer in the red worldline on the left side, and what it is to an observer in one of the blue worldlines in the graph on the right side. In the graph on the left side, two blue objects moved past the red object very...
  13. rudransh verma

    Understanding Fog Formation and Dew Point from Wikipedia

    I read in Wikipedia that fog is formed when the water vapor in air is condensed to form liquid water that are suspended around condensation nuclei. Fog or clouds don't move from some place but appear in places through condensation. Now there is something about dew point which has to do with the...
  14. haushofer

    I Black hole formation watched from a distance

    Dear all, For a new book I'm writing I'm investigating some common misconceptions in physics. And of course, that means confronting myself with my own confusion. One thing I've never got clear in my head, and which I find hard to answer using google and my textbooks on GR, is the following: how...
  15. G

    I Planetary Formation: Could Collisions Explain Our Solar System?

    I'm very much an amateur with a keen interest in space/the universe and it occurred to me the other day that our solar system could have been formed in exactly the same way that it is hypothesised that the Moon/Earth system formed through the (proposed) collision of Theia and the proto-Earth...
  16. Ranku

    I Dark matter and structure formation

    Could matter have formed structures in the universe, like galaxies, without the presence of dark matter?
  17. N

    A Sine Dipole formation using two hydrophones

    Hi all. I am trying to do MATLAB simulations for generation of SINE Dipole using two hydrophones spaced distance 'd' apart for signal coming from direction 'DOA'. The MATLAB code is given below. The confusion is that there is constant phase difference of 90 degree b/w SINE Dipole generated using...
  18. E

    B Meniscus formation in a beaker

    I will refer to this paper for some relevant bits of theory. They write that the component of the force between the solid and liquid parallel to the solid-liquid interface, which appears near the contact line (in the dotted region), is ##\gamma_{SV} + \gamma_{LV} - \gamma_{SL}##, which by...
  19. HighFive5

    Chemistry Reaction Mechanism for Amide Formation: Do You Agree?

    Hello all! I wrote a reaction mechanism for a sequence that forms an amide. Do you agree with my answer? Thanks for your help!
  20. cookiemnstr510510

    Chemistry Why does a negative ΔH indicate an exothermic reaction?

    Hello All, I wanted some insight on my answer to this problem. Lets say we have the reaction PCl3(g) + Cl2(g) ↔PCl5(g) ΔH0=-111KJ So for this reaction we know it is exothermic (because my textbook told me). But I want to make sure I understand why it is. If I were to look at this reaction and...
  21. kolleamm

    Thoughts on the early formation of life

    I watched a video lately describing how life could have arisen on Earth near the hydrothermal vents, with the exact way it formed being unknown. This made me wonder could there be a very simple configuration of DNA (or RNA?) that could give rise to life? I'm thinking the earliest life forms may...
  22. pinball1970

    This paper suggests that the Earth's formation was earlier than first thought

    Here is the paper. I have ran it by one of the guys first https://advances.sciencemag.org/content/6/7/eaay7604.full In terms of abiogenesis does this have any impact? Water also.
  23. Natalie456

    Chemistry How Can Isoxazole Be Synthesized from Furoxan and Phenylacetylene?

    I'm having difficulties uploading my work to this system at the moment, but I have currently attempted 1,3-cycloaddition between the furoxan and phenylacetylene. However, unless a sigmatropic rearrangement occurs (which, as far as I can conclude, leads to instability with charges), this places...
  24. B

    Why do I observe ice formation on the exterior of this pipeline?

    Hi all, I would like to ask why is there ice formation on the exterior of the pipes between compressor to reactor when there is no flow passing through or what kind of phenomenon is this? My colleagues have suggested PV=nRT and adiabatic process as the possible reasons but I still feel that...
  25. rachelmaddiee

    Chemistry Formation of Ionic Compound MgO

    Here is my work** Magnesium cations (Mg2+) Oxide anions (O 2-) A magnesium ion has a 2+ charge and the oxygen atom has a 2- charge. The formula for the ionic compound is MgO.
  26. A

    I Formation of dark matter structures

    I can't understand how dark matter can form structures from the initial near uniform distribution as shown in simulation like those of the Eagle project http://icc.dur.ac.uk/Eagle/index.php. I understand how the initial density fluctuation are amplified and dark (and ordinary) matter start to...
  27. HydrogenBurns

    Astrophysics Introductory books on Star Formation

    So as the title suggests, I'm looking for some introductory books on Star Formation. I have a rudementary idea of the concept from a module I took last year which I found really interesting. I'm looking to apply for a research scholarship next academic year in which I would undertake a research...
  28. G

    Formation of an internally statically determinate truss

    My professor taught me that a internally statically determinate truss is formed by having one basic truss - the triangular truss consisting of three joints and three members: and then repeatedly adding two members and a joint: So, it makes sense why this is a statically determinate truss...
  29. J

    Standard enthelpies of formation of carbon nanotubes etc.

    I am curious about the standard enthalpies of formation of carbon nanotubes, diamond, carbon buckyballs, graphene, etc. I read from physics forums that the standard enthalpies of formation of these allotropes of carbon are small. However, since diamond is fabricated naturally under extreme...
  30. Ranku

    I Cosmological constant and structure formation

    How much impact does the presence of the cosmological constant have on the formation of structures in the universe? On a larger scale, is there less structure formation because of the presence of the cosmological constant?
  31. I

    Coal vs Oil Formation: What's the Difference?

    So I'm learning in a class that coal is made when land plants (in swamps) die and then get buried in sediments, and with the Earth's pressure/temperature the plants become coal. Then I learned that when ocean plants (like algae and plankton) die, they also get buried in sediments in the sea...
  32. koulbichok

    I Gaussian probability distribution of formation PBH

    Hello. If we consider PBH formation from collapse of large density perturbation in the early Universe, a mass PBH depends on density contrast as And δ must be larger then . Also we have β — an abundance of black holes, it's the ratio of the PBH energy density to the total energy density, this...
  33. E

    Entalphy of Formation: Why Use Water at Std Cond?

    why do we use the entalphy of formation of water at standard conditions to calculate the entalphy of a reaction even if water is not gas at 1bar and 298K
  34. Green dwarf

    I Formation of super-massive black holes

    It seems that the super-massive black holes at the centres of galaxies formed very early in the history of the galaxies (e.g ULAS J1342+0928, which had about 800 million solar masses 13.1 billion years ago). Presumably, in the very early days, matter in the universe was much less clumped than...
  35. D

    How do I calculate the enthelpy of formation using combusion data

    The enthalpy of formation equation: ΔHƒ°reaction=∑Δhƒ°(products)-ΣΔHƒ°(reactants) When using the enthalpy of formation equation you get: -2010-((-394x3)+(-286x4))= 316Kjmol-1 However, this answer is wrong. On the mark scheme, the answer is -316Kjmol-1. So I used the enthalpy of combustion...
  36. B

    I Atmospheric Lapse Rate (calculating the altitude of cloud formation)

    This is probably more of a p-chem question but I figure you guys are smart enough to answer this. FREEZING LEVEL CALCULATION: Per FAA "A standard temperature lapse rate is when the temperature decreases at the rate of approximately 3.5 °F or 2 °C per thousand feet up to 36,000 feet" Easy...
  37. F

    B Does galaxy formation conserve mass and angular momentum?

    Last week I posted in General Physics some questions about what happens in a collapsing gas cloud, and I was advised that total angular momentum is conserved. I thought of asking for extra clarification here, as that seems really amazing -- I apologize for asking the same thing twice. I use a...
  38. barryj

    Formation of a hyperbola using a plane cutting a doubole con

    Homework Statement My question. When studying conics, the parabola circle, and ellipse can be easily see by passing a plane through a double cone. The hyperbola is generated when the plane is passed through the double cone where it passes through the top and the bottom cone. My question is...
  39. R

    B Formation of Supermassive Black Holes

    Are there theories to explain the formation of supermassive black holes?
  40. T

    Plastic formation in cast-iron pan

    Yesterday morning, before work, I cooked eggs in canola oil in a cast-iron pan. Afterward, I rinsed out the pan and heated it to dry it. By mistake, I left the stove on. When I returned home, in addition to my house being smokey and smelling like IHOP, my cast-iron pan was lined with a...
  41. M

    No covalent bond formation due to repulsion

    Hi, I want to ask , is there any example in chemistry when during covalent bond formation the repulsive forces dominate and no bond is formed. Thanks
  42. S

    Equal electronegativities and covalent bond formation

    Homework Statement True or false: When two atoms are equally electronegative, they will interact to form polar covalent bonds. Homework Equations Atoms with similar or equal electronegativities share electrons between them and are connected by covalent bonds. Atoms with large differences in...
  43. B

    Force of constraint in Lagrangian formation

    Homework Statement A mass m slides down a frictionless plane that is inclined at angle θ. Show, by considering the force of constraint in the Lagrangian formulation, that the normal force from the plane on the mass is the familiar mg cos(θ). Hint: Consider the Normal force to be the result of...
  44. Glurth

    I Transition from Normal Matter to Black Hole: Thought Experiment

    Thought experiment: single use of "magic" Setup: Let's assume we have a giant ball of water in space. Magic: Let's assume the water does not compress its center under its own gravity. (Constant density of 1 g/cm^3) Basic stuff: The mass of this ball of water, (since it does not compress)...
  45. Harsha Avinash Tanti

    I The Role of magnetic field during the formation of small to medium scale stars

    Hi, I would like to raise a question about Role of magnetic field while formation of small to medium scale stars emerging from nebula ?
  46. R

    Radicals again - Formation energy

    I know my last question on radicals' interaction with luminol didn't get much attention, perhaps it was too specific. Please could I ask a last question, I understand that when radicals are formed via bond breaking this is called the bond-dissociation energy, but is there an energy associated...
  47. D

    I Star formation and heavy elements

    Hello. First post here so hi all. My question(s) is regarding the formation of solar masses by accretion of gases and dust. From what I understand, stars are formed by large clouds of gasses and dust particles pulling together and with enough gravity, (magnetic fields), and time. A fusion...
  48. MrGenetic

    Does this bond formation release energy?

    If -Nh2 terminal become Nh3+, is this bond formation release energy in terms of entalpy decreasing way?
  49. Spinnor

    B New theory, our solar system formation, "space bubble"

    "There are various theories about how the solar system formed, but scientists haven't been able to agree on a single model that explains all the quirks of our corner of space as it exists today. Now, scientists at the University of Chicago have...