What is Rocks: Definition and 78 Discussions

A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition and the way in which it is formed. Rocks form the Earth's outer solid layer, the crust, and most of its interior, except for the liquid outer core and pockets of magma in the asthenosphere.
Rocks are usually grouped into three main groups: igneous rocks, sedimentary rocks and metamorphic rocks. Igneous rocks are formed when magma cools in the Earth's crust, or lava cools on the ground surface or the seabed. Sedimentary rocks are formed by diagenesis or lithification of sediments, which in turn are formed by the weathering, transport, and deposition of existing rocks. Metamorphic rocks are formed when existing rocks are subjected to such large pressures and temperatures that they are transformed—something that occurs, for example, when continental plates collide.The scientific study of the character and origin of rocks is called petrology, which is an essential subdiscipline of geology.

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  1. Astronuc

    Rocks, ichnology, ammoglyphs - and seredipity

    Rock stars: how a group of scientists in South Africa rescued a rare 500kg chunk of human history https://www.yahoo.com/news/rock-stars-group-scientists-south-152622422.html https://en.wikipedia.org/wiki/AmmoglyphI wonder if the lines are hominid-made, or coincidentally and naturally formed by...
  2. M

    I How many piles given n identical rocks?

    Is there a technique to count the amount of piles ##p## that can be made given ##n## identical rocks? We know ##n=1 \implies p=1##, ##n=2 \implies p=2##, ##n=3 \implies p=3##, ##n=4 \implies p=5##, and so on. I'm kind of lost as to how we approach it. It seems we have ##n## piles that we can...
  3. Kstarlove1728

    Does anyone know what these rocks are? Please any info welcome

    I am so curious as to what I actually have found any input welcome please and thank you
  4. D

    I Getting a sauna to a certain temperature - faster with more rocks?

    We've been discussing what it takes to get a sauna to heat to 240F. Most sauna heaters will have some stones to provide mass to hold heat. The question is whether lots of stone mass will make it easier to reach higher temperatures. My argument is that it does. Imagine heating a room using a...
  5. jamiebean

    Deceleration of rocks sliding up a hill

    i have no idea how did the answer come in conclusion...i guess that cosθ and sinθ is referring to the 2 dimensions of the acceleration ? but how? and why?
  6. O

    I How does Jupiter protect the Earth from collision with space rocks?

    I read (in "The View From The Center") that Jupiter protects the Earth from collision with large space rocks, asteroids, etc. What I can't get out of my mind is that could it also cause collisions. A large rock (initially not heading for Earth) could be put on a different path by Jupiter's...
  7. davenn

    A SPACE ROCKS: Latest meteorite into my collection

    I have a bit of a love affair with rocks that come from outer space. To hold a piece of rock that has zoomed through space for zillions of years before finally crashing to Earth still gives me that WOW factor. I have around 55 samples in my collection from many different falls around the world...
  8. sepcurio

    Why do I keep finding more new rocks in my garden year after year?

    I can completely clear out all large rocks from my garden so it's just soil and pebbles down to about a foot. Then come next spring I find new large rocks again. Happens each year. This is a common problem for farmers and gardeners. Causes I've considered include: -- Ice heaves that push up...
  9. C

    B Do Rocks Absorb Solar Energy?

    Summary: I recently bought a rock necklace from a store and the seller asked me to charge it with the sun, so naturally I didn't believe it so I'm wondering if this is true. Can rocks be charged with solar energy and if so what can you do with it?
  10. R

    Sauna rocks: how do they work?

    I've looked at many posts related to saunas, and all have been about what happens when you pour water on the sauna rocks and so forth so I believe that question has already been answered. I've struggled to find, however, what physical mechanism governs the heating of saunas? Then, more...
  11. Eclair_de_XII

    Dropping rocks with the x- and y-coordinates being normal

    Homework Statement "A helicopter drops rocks onto a desert until it hits a marked bullseye. With respect to Cartesian coordinates whose origins is at the bullseye, both the x- and y-coordinates are normally distributed. Denote the r.v.'s taking on values along these axes as ##X,Y##...
  12. Phantoful

    Find x(t) for a car being pelted by rocks (1-D)

    Homework Statement Homework Equations p=mv K=(1/2)mv2 Integration and Derivation Methods J=mΔv The Attempt at a Solution So far I set Pbefore=(Δm*u)+(MVcar), with Vcar depending on the time that has passed (I'm not sure how I should find the function for Vcar(t). For Pafter I included the...
  13. S

    Can't we just smelt plastic into igneous rocks?

    Now cost asides...can't we just smelt plastic into igneous rocks? I'm sure we can achieve the temperature & pressure to do it. Plastics Mainly Composed of C H O N Cl S. N H Cl are all trappable within rock layers. Additives like Si and Fe can be added in various steps of heating to form silica...
  14. C

    Geometry genius designs 4-legged cafe table that never rocks

    Thought this was fascinating.. http://google.com/newsstand/s/CBIw4N3PyjU All the need to do now is make them compulsory.
  15. Sanborn Chase

    Iridium Question -- Why is Iridium plentiful in space rocks but scarce on Earth?

    Why is iridium plentiful in space rocks but scarce on earth?
  16. R

    B Move a large amount of rocks from one place to another

    I am looking to move a large amount of rocks from one place to another. I was thinking of making a sleeve out of a strong plastic that was at a 90 degree angle. Then load the rocks on. The challenge is to move the sleeve. It only needs to go about 6 feet. The rocks will weigh about 100 pounds. I...
  17. Eureka99

    Trouble with identification of minerals

    Lately I'm learning how to identify the most common rock-forming minerals, but I have some doubts about it. First of all, how can I distinguish between massive minerals and rocks? Second thing, a massive mineral from what I understood, has an internal order (so it's not amorphous), but that does...
  18. A

    What is solidus and liquidus temperature of granite?

    My understanding is that because a rock is composed of variety of minerals, so it does not have fix melting point, rather there is a range below which whole rock is solid and above which whole rock is liquid. I want to know this liquidus and solidus temperature for granite rock based on pressure...
  19. L

    B What do you call rocks that don't orbit the sun?

    I understand the difference between comets, asteroids, and meteoroids. I was just reading about asteroids recently, and it occurred to me that when I read anything about these three types of objects the implicit (and sometime explicit) assumption is that they only apply to things that orbit the...
  20. M

    Two rocks launched up/collison (Kinematics)

    Homework Statement This is a quiz question that was given in my AP physics C class. "A rock is launched upward with a speed V0. With what velocity must a second rock be launched from the same initial position at time T later so that it hits the first rock when it has a velocity of -V0/2."...
  21. PinkGeologist

    How "plastic" do you think heated rocks become?

    Consider a magma chamber in the Earth's crust ... models show that 1-2 km surrounding this chamber are heated above the brittle-ductile transition zone. Let's say that you know the yield strength of the crust in general (not heated) is 15 MPa ... and after that, rocks under heavy confining...
  22. N

    Simple collision between rocks in outer space. Webassign

    Homework Statement [/B] Two rocks collide in outer space. Before the collision, one rock had mass 14 kg and velocity ‹4450, −2950, 2250› m/s. The other rock had mass 7 kg and velocity ‹−600, 1900,3600› m/s. A 1 kg chunk of the first rock breaks off and sticks to the second rock. After the...
  23. F

    {Rocks} difference between sandstone and slate?

    Homework Statement sandstone is a sedimentary rocks while slate is a metamorphic rock come from mud stone with a high temperature and pressure, they are both stratified rocks, while chemically slates compose of Argil i.e Clay, while silica is the main ingredients of sandstone, my question is ...
  24. jbrussell93

    Geophysicist not really "into" rocks

    Is it weird for a geophysicist not to be interested in rocks? I'm a rising senior in physics who is planning to go to grad school for seismology. I'm fascinated by the large scale tectonic questions about the Earth and feel that seismology is the best approach for exploring most tectonic...
  25. B

    The Collision of Rocks - Momentum Impact

    (This is not a homework problem, but is just something I'm curious about.) If two rocks with different momentum collide, how much "damage" will the rocks receive as a function of their momentums? For example, could I figure out a momentum (in the elastic or inelastic case) that would cause...
  26. L

    What are these rocks worths? Pictures inside.

    I know a gentleman who wants to clear up his collection. 90% of these are handpicked, including the 150 lb amethyst in the last picture in post #3. Is there a market for this?
  27. S

    Mars rocks covered with uniformly thick dust layer?

    Hello all, I need your help. (I believe this si the correct forum) Between 2011 and 2013, i read a news in internet, that the dust that coveres rocks in Mars seem to be very uniform, like all rocks that was drilled by Mars science laboratory twin rovers, seem to have the same thickness of...
  28. S

    MCQ - rocks (for 11 year olds)

    Hi there I am a physics teacher but also teach all sciences up to age 13. Have encountered an mcq on rocks (that I am teaching to a class of 11 year olds (year 7))which I cannot answer: A sedimentary rock has very small grains. Which statement is true? A The grains were deposited by...
  29. K

    2D Kinematics - 2 rocks off a bridge

    2D Kinematics -- 2 rocks off a bridge Homework Statement Heather and Jerry are standing on a bridge 60m above a river. Heather throws a rock straight down with a speed of 14m/s . Jerry, at exactly the same instant of time, throws a rock straight up with the same speed. Ignore air...
  30. S

    Rocks thrown off of a skateboard

    Homework Statement A person sits on a skateboard and wants to propel themselves. The persons mass is 150 lbm whihile the skateboard mass can be ignored. The person has a bucket with 1 kg rocks totaling 10 kg. The rocks are ejected at a rate of 1 kg/s and a velocity of 108 mph with respect to...
  31. F

    Calculating Heat Absorbed & Temperature Change of Rocks

    Homework Statement Large beds of rock are used in some solar-heated homes to store heat. Assume that the specific heat of the rocks is 0.82 J/g-K. (a) Calculate the quantity of heat absorbed by 50.0 kg of rocks if their temperature increases by 12.0°C. (b) What temperature change would these...
  32. L

    Speed of rocks when they hit the ground

    Homework Statement If I throw a rock upwards with an initial velocity and throw a rock downwards, what is the speed of the rocks just before they hit the ground? Homework Equations The Attempt at a Solution\ They should hit the ground at the same speed and different times. I...
  33. T

    Volcano in mars ejects rocks. Straight line motion

    Homework Statement A certain volcano on Earth can eject rocks vertically to a maximum height . Part A: How high (in terms of H ) would these rocks go if a volcano on Mars ejected them with the same initial velocity? The acceleration due to gravity on Mars is 3.71 m/s^2 , and you can...
  34. G

    Rocks falling at the same time and their distance apart

    Homework Statement Two rocks are falling from a roof. The second one begins its fall when the first one has already covered 30cm. Calculate the distance d between these two rocks after 10 seconds counted from the moment the second rock begins its fall. Homework Equations...
  35. T

    I heard small rocks falling inside one of the walls

    I live in an apartment, and today I heard what seemed small rocks falling in one of the walls (it's a wall that goes through the center of the building), several times. Is this normal?
  36. D

    Would like suggestions for studying igneous rocks and radioactive decay

    I don't have much of a scientific background, but I am interested in learning about geology. More specifically I would like to study the nature of igneous rocks, particularly their formation through volcanic processes. I'm also very much interested in understanding how the process of...
  37. W

    Age of rocks calculation - I only need little help

    How many half lives have passed since a particular rock was formed if a sample of the rock contains 31 times as much lead-207 than uranium-235? I know that I need to do a table and calculate I know how to do this question but the thing I need help on is how do I know the number of atoms in order...
  38. Jim Kata

    How Many Rocks Will Be in the Hole at 12:00?

    Say it's 11:00 and you throw 100 rocks in a hole and at the exact same second a rabbit throws one rock out of the hole. Then at 11:30 you throw a 100 rocks in and the rabbit throws one rock out. At 11:45 you throw 100 rocks in and the rabbit throws one rock out and so on, with the time...
  39. P

    Kinematics: Initial velocity of second rock if 2 rocks are thrown up?

    Homework Statement Rock A is thrown straight up from the top of a 25m tall building at a speed of 20m/s. Exactly 1 second later Rock B is thrown in such a way that it lands on the ground at the base of the building at the same instant that Rock A lands. What is the initial velocity for Rock...
  40. D

    Conditions of igneous rocks on the early Earth

    I have a question that's related to radiometric dating. I would like to know what the condition would be of igneous rocks in their early states. What I mean is the state in which the radioactive elements found in the rocks, which are used for dating, have not yet undergone any decay. For...
  41. N

    NASA NASA Photos: Global Eruption Rocks the Sun

    "Dec. 13, 2010: On August 1, 2010, an entire hemisphere of the sun erupted. Filaments of magnetism snapped and exploded, shock waves raced across the stellar surface, billion-ton clouds of hot gas billowed into space. Astronomers knew they had witnessed something big. It was so big, it may...
  42. C

    Infinite Rocks Collide: Is the Impact Elastic?

    If an infinitely large rock is traveling infinitesimally slow along a straight line and an infinitesimally small rock is traveling infinitely fast towards the infinitely large rock along the same axis, is the collision elastic?
  43. M

    Flight of rocks thrown through the air

    This has been bugging me for 30 years, so I hope someone here can help. I was at the base of a local Dam that had a fish hatchery on top, and a HUGE flock of hawks circling above, waiting to get lucky. Yum! In a totally non-PC way, I started throwing rocks at the hawks. My 'lead' on them was...
  44. Pattonias

    Questioning "Proof" of Past Life on Mars Found Through Rocks on Earth

    I'm skeptical of "proof" of past life on Mars as as result of rocks found on Earth. I'm skeptical of "proof" of past life on Mars as a result of rocks found on Earth. http://www.digitaljournal.com/article/285660" Wouldn't real proof be found on the planet? I thought these Martian...
  45. F

    Why Do Two Stones Thrown Off a Cliff Make a Single Splash?

    Homework Statement A person climbs 50m cliff that overhangs calm pool of water. He throws two stones vertically downward, 1s apart, and observes that they cause a single splash. The first stone has an initial speed of 2m/s downward. (a) How long after release of the first stone do the two...
  46. T

    Exploring Layering in Igneous Rocks

    are igneous rocks layered?
  47. P

    Rocks thrown out of a window problem.

    Homework Statement In a sticitly scientific experiment, a student athlete throws rocks out the window in all directions. All rocks have the same initial speed V. It turns out that all rocks' landing velocities make angles theta or greater with the horizontal. Find height h of the window above...
  48. S

    How do alkaline rocks get so enriched in alkalis?

    How do alkaline rocks get so enriched in alkalis and incompatible trace elements ?
  49. S

    Middle and end members of fractionation series of high alkaline rocks

    Name the middle and end-members of fractionation series that start with: a) basanite-tephrite b) trachybasalt, c) hawaiite.
  50. 1

    How far apart are the two rocks?

    Homework Statement From the top of a 40m high cliff, two rocks are simultaneously thrown. One is thrown upwards at 20m/s, the other is thrown downwards at 8.0m/s. How far apart are the two rocks after 1.5 seconds? Homework Equations vf = vi + at d = Vavg * t d = vit + 1/2 at^2 vf^2 =...
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