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. sevenperforce

    Stellar-mass black hole formation sequence

    I feel like this could go in quite a few of the Physics subforums (Quantum Physics, Beyond the Standard Model, Special and General Relativity, or High Energy, Nuclear, Particle Physics) instead of Astronomy and Cosmology, but hopefully this will work. This is my first question I've posed here...
  2. N

    Rapid Formation of the Moon: Insights from Theia Impact

    From what I've seen on shows like how the universe works and the Wikipedia article on Theia, they are saying that the moon was formed in less than a year after the impact. My question is, how did that happen so quickly? I am simply a fan of watching shows like that or reading articles about...
  3. Sace Ver

    Strontium Nitrate and Ammonium Hydroxide Reaction: Formation of Precipitate

    Homework Statement Strontium Nitrate + Ammonium Hydroxide = Homework Equations Finding net ionic equation The Attempt at a Solution Balanced Equation: Sr(NO3)2(aq) + NH4OH (aq) = Sr(OH)2(aq) + NH4NO3 there is no precipitate correct? I will not need to find the net-ionic equation.
  4. caters

    How Do Rivers and Lakes Form and What Determines Their Type?

    I have heard that rivers form from meltwater and rainwater flowing down mountains. But I know that not all rivers start near mountains. As an example the Mississippi river doesn't start near any mountains. Rather it starts at Lake Itasca which is surrounded by taiga(coniferous forest). This lake...
  5. I

    I What caused this unique ice formation near freezing temperatures?

    this ice formation occurred with temperature hovering near zero C. It looks like something that was made in a mould! I suspect that a combination of winds and pressures caused by growing ice crystals in the plastic bucket tilted some crystals which continued to grow. I
  6. F

    Reflection of Waves and Formation of Standing Waves

    I have three doubts in regard to waves on a string which I will try to make as clear as possible. For this purpose, I have considered a general wave: $$y_i=y_0\sin(\omega t - kx)$$ (1) If a wave pulse: $$y = y_0 e^{\frac{-1}{T^2} \left(t-\frac xv \right)^2}$$ is incident against a rigid...
  7. C

    Lagrangian mechanics and planetary formation

    I am disappointed by my graduate-level classical mechanics course, and especially the treatment of Lagrangian/Hamiltonian mechanics. Now, I scanned my notes and some crazy idea popped into my head, further fueling my discontent towards this course, because all the problems covered in class were...
  8. A

    I What's the fate of neutrons in black hole formation?

    I understand how the neutron stars are formed, and why the electron degeneracy pressure collapses as electrons are absorbed by protons, by photo disintegration. However, I'm struggling to grasp what happens when the gravity is large enough to overcome neutron degeneracy pressure. Apparently a...
  9. Chronos

    Notes on Star Formation: A Primer for Stellar Formation

    Here; http://arxiv.org/abs/1511.03457, Notes on Star Formation, is a primer for those with an unnatural desire for a graduate level textbook discussion of stellar formation. Fair warning, it is not for the math challenged.
  10. Etienne

    Electrochemistry Question -- Which cell reaction will proceed toward the formation of more products

    Homework Statement The E° value of one cell reaction is positive and that of another cell reaction is negative. Which cell reaction will proceed toward the formation of more products at equilibrium? *Problem 19.20, Chemistry: Chang, Raymond. 10th ed. Homework Equations E° cell = E° cathode -...
  11. K

    Standard enthelpy of formation

    Homework Statement I have the following task: The Standard enthalpy of formation of gaseous H2O at 298K is -241.82 kJ mol-1. Estimate its value at 100 °C given the following values of the molar heat capacities at constant pressure: H2O (g): 33.58 JK-1mol-1, H2 (g): 28.84 JK-1mol-1, O2 (g)...
  12. P

    Why are images formed when rays intersect?

    In most (perhaps all) books it was mentioned that intersection of the light from the object when reflected by the mirror or refracted by a lens intersect at a particular point. That point when traced till the principal axis gives the image. (Provided object lies on the axis). I do not understand...
  13. I

    About wavefronts/wavelets and the formation of plane waves

    The photography book I have talks about waveforms, but it doesn't do a good job of explaining them. So, here's my understanding from the book and google searches (it could be unbelievably wrong.) In an isotropic homogenous medium, light will spread out in all directions, essentially forming a...
  14. T

    Creating Realistic CTCs in GR: Is it Possible?

    I know there are solutions with CTC, I know about: 1. Goedel Universe 2. Case with moving infinite sticks 3. Ring singularity inside the rotating BH However, in all 3 cases above CTC is "eternal" - the universe "always" contains CTC, and case 3 is a part of the "eternal" BH, We know...
  15. T

    Formation of bonds and heat release

    Hello, We know when there's formation of bonds during chemical reaction there's heat release to the surrounding due to conservation of energy. But what I am confused about, is the kinetic energy of the surrounding increase or the kinetic energy of the atoms that made the bonds increase? if it...
  16. S

    About the formation of crops circles.

    I don't know where I should ask this question. I don't even know the appropriate thread level anyway. Ignore those stuff. I feel this topic is interesting because I don't understand something. We are using so many satellites. Why can't these satellites record the formation of the crops circles?
  17. ryanuser

    Formation of Zinc Oxide: Can Metal Strip be Oxidized?

    Hi I am aware that Zinc Oxide (ZnO) is in the form of white powder. Can I leave a strip of Zinc in a room (at presence of Oxygen) so that it becomes oxidised therefore the same thing is resulted but in form of a metal strip instead of powder? Would the resulted strip become as oxidised as the...
  18. anorlunda

    Planetoid formation, spherical or not.

    I am interested in the minimum size of a rocky planetoid needed to "crush" it into spherical shape. I'm also interested in its initial temperature because liquid or plastic masses obviously need much less crushing. The Wikipedia article "Giant Impact Hypothesis" says, In 2007, researchers...
  19. wolram

    The impossible early galaxy formation

    Is there general consensus that the universe is to young? arXiv:1506.01377 [pdf, ps, other] The Impossibly Early Galaxy Problem Charles L. Steinhardt, Peter Capak, Dan Masters, Josh S. Speagle Comments: 7 pages, submitted Subjects: Astrophysics of Galaxies (astro-ph.GA) The current hierarchical...
  20. E

    A Question about the formation of white holes off black hole

    Hello, I had a thought about the formation of white holes off of black holes and i wanted to ask if it is possible, if a massive black hole is surrounded by a lot of matter(a lot of giant stars etc.) and it consumes so much matter that even a aquasar is not sufficient enough in disposing all of...
  21. N

    Can Color Singlets Be Formed for Baryons and Mesons?

    I am trying to conceptually understand how form a color singlet for baryons and mesons. For example, the Wikipedia article http://en.wikipedia.org/wiki/Isospin shows how to construct the proton and neutron states in terms of isospin and spin. How does one create a color singlet corresponding...
  22. P

    Concept: Question on formation of parallel capacitors

    1. So my teacher gave us examples of how to solve capacitor problems. I know how to solve the problem but I don't this problem's particular "formation" of parallel capacitors. In this problem, my teacher says C3 and C4 are parallel but when I did the problem, I assumed it was series. Can anyone...
  23. davidbenari

    Questions on the Urey-Miller experiments (OrgMol. formation)

    My knowledge of Earth science is basically null so please bear with me.My first question relates to the soundness of assuming a primitive atmosphere rich with H2O CH4 NH3 and H2 gases (Also not too much presence of O2, as the Urey-Miller atmosphere has to be a "reducing atmosphere"). The...
  24. gracy

    What are the two types of ATP synthesis and how do they differ?

    I came across a term "indirect atp formation"I am not sure what it is ? What is the difference between direct and indirect atp synthesis?I think substrate level phosphorylation (where a molecule directly donates a phosphate to ADP) is direct atp synthesis.Indirect atp synthesis is oxidative...
  25. gracy

    Condition for formation of ionic bond

    In my textbook one of the conditions for formation of ionic bond is given as The cation should be large and anion should be small But in the image of Nacl lattice structure ,we can see that it is other way around I am not getting the reason,Is my textbook wrong ? Or it has something to do with...
  26. B

    Standard enthelpy of formation water

    Homework Statement The standard enthalpy of formation for liquid water is: H2 = 1/2O2→H2O ΔHf=-285.8 kJ/mol Which of the following could be the standard enthalpy of formation for water vapor? (A) -480.7 kJ/mol (B) -285.8 kJ/mol (C) -241.8 kJ/mol (D) +224.6 kJ/mol Homework Equations NA The...
  27. TheExibo

    Multiple Choice Question about Enthelpy of Formation

    Homework Statement The term chlorine is used to mean a number of possible types of matter containing chlorine atoms, such as Cl2(g), Cl(g), and Cl-(aq). Which of these forms of chlorine would have a zero standard enthalpy of formation? a) Cl2(g), Cl(g), and Cl-(aq) b) Cl(g) c) Cl-(aq) d)...
  28. thegirl

    Forming Stars: 2 Conditions and Criteria Explained

    2 conditions to form a star - all atoms in the gas cloud must be gravitationally bound to each other (so the virial theorem applies) - the cloud must permanently lose overall energy E=-GMm/2R therefore R=-GMm/2E, so for R to become smaller and the energy to also become smaller the energy needs...
  29. Monsterboy

    Doubts about nebulae and star formation

    I read that nebulae are formed by stars exploding and they are also thought to be the birth place of stars. Stars explode when all the hydrogen atoms are fused into heavier elements and they are no longer able to fuse heavier atoms right ? If that's the case then the nebulae should contain...
  30. C

    Mechanism for Phosgene Formation

    The overall reaction for the formation of phosgene from Cl2 and CO is: Cl2 + CO --> Cl2CO The mechanism is: Cl2 + M <--> 2Cl' + M Cl' + CO <--> ClCO' ClCO' + Cl2 --> Cl2CO + Cl' For this mechanism, the sum of the elementary reactions is: 2Cl2 + CO --> Cl2CO + 2Cl' However, doesn't the sum...
  31. RJLiberator

    True/False Igneous Rock Formation Question

    Homework Statement Huge volumes of igneous rock can be erupted and/or intrude in the middle of tectonic plates? True or False Homework EquationsThe Attempt at a Solution I am being thrown off by this rather simple problem. I understand that at the border of tectonic plates, a lot is...
  32. S

    Finding the electric field at point p in this formation?

    Homework Statement What is the magnitude of the electric field at point p due to the four point charges shown? The distance d is between charge centers. Homework Equations Electric Field = kq/d^2 Coulomb's Law = k(q1q2)/d^2 The Attempt at a Solution I don't know how to go about solving this...
  33. F

    Adiabatic Process in cloud Formation

    I am going to report about Adiabatic process, specifically in cloud formation. Can someone help me some important points to consider?Im more concerned in cloud formation only since my topic is limited in that matter. 1. What is the science behind the adiabatic process in clouds? 2. Some...
  34. enorbet

    Exploring the Formation of Shock Diamonds

    Greetings Recently I read that radio jets from Quasars and Radio Galacies exhibit a behavior similar to shock diamonds which reopened a creaky old door in my mind because i first started reading about Shock Diamonds as a child of about 8 which may be part of my difficulties in understanding this...
  35. gracy

    Standard Enthelpy of formation

    substances in their elemental state have enthalpies of formation equal to zero,why?
  36. C

    Image formation in terms of electromagnetic waves

    In texts on geometrical optics I have read that an image is formed where light rays converge -- without an explanation of why. Thus I ask, why are images formed where light rays converge? In particular, what is the answer to this question in terms of the wave theory of light (Electrodynamics)...
  37. nicolauslamsiu

    Can a star with thousands of solar masses be formed?

    Can a extremely massive star ( eg. thousands solar masses) be formed?
  38. Y

    Question about formation of deuterium

    I wanted to ask about the formation of deuterium in a star. I read that two protons will join together and that one of the protons will transmute to a neutron due to quark transformation via the weak interaction that will generate a W boson which decays to a positron and a neutrino. It is not...
  39. Spinnor

    "Planet formation captured in photo"

    From BBC news, http://www.bbc.com/news/science-environment-29932609# "The clearest ever image of planets forming around an infant star has been taken by the Alma radio telescope. In a vast disc of dust and gas, dark rings are clearly visible: gaps in the cloud, swept clear by brand new...
  40. M

    Forming an Excimer - Explaining the Process for Xenon

    Hello, first post! Can anyone explain to me how an excimer is formed? Considering Xenon. I've gathered that an excited state Xe*, ground state Xe, and a 3rd body M react resulting in an Xe* excimer + M(carrying away excess energy). I'm struggling to find how the ground state Xe can have any...
  41. J

    Enthelpy of formation at non standard conditions

    Hi, I want to know the enthalpy of formation of Ga2O3 and Ga2O at low pressure (ultra high vacuum) and high temperature. Temperature seems easy, but I'm not sure how to get the enthalpy values for low pressures. Does anyone know if there are books with enthalpy - pressure diagrams of these...
  42. rjbeery

    Black hole formation with golf balls in GR

    Start with an existing black hole and an event horizon radius R at time T. Say the black hole is being "fed" an infinite series of golf balls, one after the other, which are all stamped numerically such that the current golf ball external to the event horizon is 1.0 * 10^32. See linked img...
  43. W

    Explore Formation of Bound State in a Delta-Function Potential Well

    Homework Statement We learned in class that a particle exposed to a 1D delta-function potential well would always have a single bound state. Let us now explore this question for the case where the delta-function potential well is situated in the vicinity of the impenetrable potential wall...
  44. bcrowell

    Backreaction from Hawking radiation may prevent formation of event horizon?

    I'm trying to understand the ideas in this paper at a nontechnical level: Laura Mersini-Houghton, "Backreaction of Hawking Radiation on a Gravitationally Collapsing Star I: Black Holes?," http://arxiv.org/abs/1406.1525 She says: This work investigates the backreaction of Hawking radiation on...
  45. Y

    Helium formation during nucleosynthesis

    If Helium is a more stable element than Hydrogen, then why wasn't just Helium formed during the process of nucleosynthesis? The matter could just have formed Helium. What was the thing that prevented it?
  46. wolram

    Galaxy Formation: Searching for Primordial Origins

    When trying to work out how galaxies formed, there must have been some seed; some perturbations that started the ball rolling, These perturbations which collapsed gravitationaly to form seed galaxies must have been primordial in origin, where did they come from?
  47. W

    Estimate the standard enthelpy of formation

    Homework Statement The standard enthalpy of formation of the metallocene bis(benzene) chromium was measured in a calorimeter. It was found for the reaction Cr(C_6H_6)_2(s) --> Cr(s) + 2(C_6H_6)(g) that \Delta_r U~at~583 K = +8.0 kJ/mol . Find the corresponding reaction enthalpy and estimate...
  48. J

    Dark Matter. Space-Time curvature. Galaxy formation

    1. Gravity is the geometric curvature of space-time caused by massive objects. 2. Dark Matter surrounds galaxies. 3. Dark Matter is thought to be critical in galaxy formation. 4. The mass of Dark Matter creates curvatures in space-time around baryonic matter which forms galaxies. What roles...
  49. G

    Standard enthelpy of formation needed for EDTA metal complexes

    Hi, I am trying to solve the chemical equilibria in a kraft mill bleach plant to predict mineral scale deposits. I am using the van't Hoff equation to account for temperature dependence of the formation constants, but I need the enthalpy of reaction for all equilibria and I am missing some...
  50. T

    The formation of shockwaves and the role of Alpha particles in ICF

    I have three questions about ICF, in the explanations i have read on the internet about ICF they all explain that the top layer of the pellet or the ablator is heated till it explodes and produces a reaction force which compress the D+T fuel. They then say shock waves are formed due to the...
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