Explain how geologic time can be estimated by multiple methods?
149966
Steno's Principles\nOriginal horizontality- Strata was orginally deposited horizontally in layers due to gravity.\nOriginal Lateral Continuity- Strata will continue until it tapers off or hits the edge of a basin.\nCross-cutting Relationship- The intrusive strata is younger than the strata they cut through.\n\nIncluded fragments- Inclusions are older than its host rock.\nFossil Correlation- If same fossil assemblages in similar rocks than rocks the same ages.
1100973
Identification of a sedimentary facies (or any rock facies, for that matter) requires an intimate knowledge of the type locality of that particular facies, what major minerals constitute the lithogenics, and what the depositional/erosional/tectonic activity of the region was like since the formation of the facies.  \n\nFor example, when I was out west I was able to trace the Navajo sandstone throughout the four corners region, from the Grand Canyon all the way up through Utah.  There were points where the Navajo was the thickest facies, while in other regions the Navajo was very thin and nearly unnoticeable.  In those thin regions, the deposition of the Navajo might not have been as pronounced (sedimentary facies are formed by deposition of sediment), or the facies could have been exposed at the surface much longer than in other regions and subsequently eroded away.  You can determine if this happened by looking for unconformities between the Navajo and the facies above it.  \n\nHowever, there are certain characteristics of the Navajo (Aeolian remnants, highly silicic, slight oxidation) that make it the Navajo formation.  Despite the varying thickness of the facies, you can trace these rock characteristics throughout the American Southwest.  So yes, if a geologist wishes to determine the full extent of a lithogenic facies, they must attempt to trace that facies as far out as they possibly can, which means a lot of survey work.\n\nWhat most geologists do nowadays is check the state geological maps of the regions they're interested in and look for rock facies that match the facies of the rock they're studying.  Oftentimes facies that are the same facies are given 2 different names in different state geological maps.  If this occurs, the type locality of the rock is determined (IE, the best-represented sample of that rock), and the facies name is given based on the state the type locality is in.
949488
Radiometric dating is extremely reliable when it is used correctly. Anti-science propagandists like to pick out the few examples where the technique was misused in order to give the impression that the technique itself is flawed (their favorites are carbon-dating mistakes where the user didn't consider - or was actually testing - the 'reservoir effect'). This example however, is worse, as it is a case of deliberate misuse of the technique by a Creation 'scientist'.\n\nYes, it is true that the rocks produced such 'ages'. HOWEVER, dacite is a porphyritic rock - it contains xenocrysts of older crystals. But more importantly, Steven A. Austin (I'll name and shame) sent the samples to a lab which clearly states that their Potassium-Argon equipment cannot accurately measure samples less than two million years old!! Hence he deliberately mis-used the technique for propaganda and deception value. Disgraceful.\n\nAs well as the excellent links given above, it is worth emphasizing that  there are dozens of different isotopes, with different half-lives, that can be used in radiometric dating. The different decay curves always converge on the same ages (when used as they are supposed to be used), a mathematical impossibility if there was a problem with the method.
457200
Chronicling the duration of geologic eras via the strata of earth formations.
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There are a lot of different dating techniques.  (The second link talks about some) Usually, when dating something, you don't just use one technique one one sample--you try to find a few different ways, and use them to build up a case for the age of something.\n\nSome dating systems are relative, in that they can only tell you which came first.  This is useful because it lets people assemble a chronology of things, even though it won't have absolute dates.  Once you have this chronology, you can use absolute dates to start finding approximate ages for things. For example, there's a distinctive layer of iridium in many rocks. If you find something below that layer, it's a good bet that it's older than the layer is.  Once you know that the layer was put down about 65 million years ago, you can start to narrow down the date of the things beneath it.\n\nRelative techinques are also useful as a test for the absolute techniques--if you know what order things happened in, you can use that to check that other techniques are giving sensible results.\n\nThere are also a lot of different absolute techniques--see the third link for a disscussion. Some, like counting tree rings, are very accurate, but only go back a few hundred or thousand years. Others, like carbon-14 dating, work on things that were once alive.  Still others, like Uranium-Thorium dating or archaeomagnetism, only work on certain kinds of rocks. Carbon-14 and U-T dating work by looking at how much radioactive materials in the sample have broken down, and archaeomagnetism works because the Earth's magnetic field has changed over the ages, leaving signs in some minerals.\n\nFinally, you can just look at the things that are near a sample.  So, if an archelogical dig contains a kind of pottery that you know was used 3000 years ago, that's a clue that the site is about that old.  If a layer of rock is full of fossils of animals that lived 300-200 million years ago, the rock was probably formed around then.
643922
No doubt, it's a fact. Besides all evidence already discussed by other answerers (earthquakes, fossil record, continent shapes, geological models), today there are *direct measurements* of the changing distance between tectonic plates, using laser or radio interferometry (see reference).
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Man, read up on decomposition, then read up on the conditions needed for fossilization/petrifaction.\n\nIf you have some time left over, either make a study of grammar, or learn to read aloud what you write to see if it makes any kind of sense.\n\nHomo sapiens shows up in the fossil record one hundred thousand years ago, not millions of years, you're off by an order of magnitude.
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Primary, compression or P-wave and Secondary, shear or S-wave seismic waves have been created at the same point by a seismic disturbance. \n\nThe P-wave reaches the observer first and the S-wave which is slower then arrives.\n\nRock has different densities and hence the velocity of a seismic wave would vary but to a certain degree since both waves have passed through the same rock then the difference between the S and P waves can be used for calculations.\n\nTo calculate how far away the P and S waves were created multiply the time in seconds between the P and S waves by 8 kilometres per second.\n\nTherefore 8*(3*60)= 1440 kilometres or 894.8 miles.
1049902
The official answer is that the rock itself dates clear back to the precambrian. That is OLD, somewhere between 700 and 4700 million years ago.
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This is a complicated question to answer completely, but there are some things one knows.\n\n1. S waves will not travel through fluids since they are tranaverse waves. If there is a part of the earth (like the outer core) that S waves will not travel through, then you know it is fluid. \n\n2. Different types of materials have different speeds of P and S waves\n\n3. Waves can get trapped at boundaries and get to the destination faster (head waves)\n\n4. Waves will bounce off boundaries between two different materials, and show up in the recordings. \n\n5. There are formulae giving speeds of P and S waves in terms of the continuum mechanical properties of the material. \n\n6. The phases, frequencies, and amplitudes, phase and group velocities, travel times, etc of the waves that travel through the earth are all data that can be used to infer the earth's structure. \n\nThere is a lot of analysis that is conducted on seismic data to produce pictures of the interior. The signals are carefully processed, and then turned into pictures of the interior. \n\nOf course, there is a lot more detail in all of this, but this should give you a general idea to start.\n\n----------------\n\n\nHere is a my answer to a previous question about this that might be helpful:\n\n  \n\n\n \n\nThe types of seismic waves, and their amplitudes and speeds, that are transmitted through a material depend on the properties of the material. \n\nFor example, transverse waves will not travel through liquids, only solids. So the transverse S waves produced by a seismic event will not pass through the fluid inner core of the earth. Different layers between different types of materials in the earth produce reflections, so looking at the reflected seismic waves can tell something about the structure and the boundaries between regions in the earth. \n\nMore sophisticated methods for imaging the earth's interior can also be constructed. Seismic simulations can be produced and the models that produced these simulations compared with the observed seismic signals. Using exhaustion or more sophisticated optimization techniques, scientists can refine these models of earth structure. More advanced inverse methods can be developed to infer features of earth structure. \n\nInstead of using high frequency seismic waves, one can look at a seismic modal decomposition, and then develop terrestrial models that reproduce the frequencies, amplitudes and phases of the observed free oscillations using inverse methods.\n\nThe actual details can be quite complicated, and many aspects remain open problems.\n\n-----------\n\nI have attached a link to the previous question and answers that are similar.
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OK, first geography is NOT geology *sigh*\n\nLook up carbon dating; you can either tell by the degradation of carbon or by basic layering (what's on the bottom is older than what's on the top).
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Geologists don't really know. And carbon dating has been proved to be inaccurate.\n   Just recently a geode was found.  A geologist looked at it and said it was 22 million years old, but when they x-rayed it they found a spark plug inside.  Guess what the spark plug was from 1961!!!!!  There are a lot of things being discovered in coal mines .     The coal layer is supposed to be 200 million years old but what are iron pots and brass bells and human bodies doing imbedded there.  They even found a concrete wall in one coal mine!!  Kind of makes you wonder about these things doesn't it?\n   The Bible says man has only been around about 6000 to 6500 years on the earth.
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Geologic time goes back millions, if not billions of years. For example, dinosaurs first appeared on earth between 200 and 240 million years ago, in a time period known as the Triassic. They lived through the Jurrassic until the Cretaceous (65 million years ago) periods. \nIn short geologic time is a time scale that has been put together based on fossil and other evidence to depict the earths past from formation (4.5 billion years ago) to present time.
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The first thing to understand is that no geophysical method can tell what  rock exist in the subsurface. The geophysical methods are basically the response of the rocks to some invading signal or  measurements of some physics-chemical attributes. This information or data is correlated with the known geological information of the area.\n Now ur question to know kimberlites through seismic methods - due to density contrast and disposition of kimberlites the seismic waves response would indicate an anomaly. Now if the kimberlite pipe is not exposed or does not have a show, it would be difficult to come to a definite conclusion about the presence of kimberlite pipe. The imp. query would be what is the country or enveloping rock of the kimberlite pie and what is its depth? But an experienced geophysicist  with available geological information can at least say that a pipe like feature is expected. Normally for such targets a single method is seldom useful, multiple methods are normally employed in exploration to arrive at a definite interpretation. Gravity method could be very useful for kimberlite pipes in areas with density contrast.
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What you want to do is best done by a science called Dendrochronology:\n \nology: the study of \nchronos: time, or more specifically events in past time \ndendros: using trees, or more specifically the growth rings of trees \n\nApplications in dendrochronology include: \necology: insect outbreaks, forest stand structure, past fires\nclimatology: past droughts or cold periods \ngeology: past earthquakes, volcanic eruptions \nanthropology: past construction, habitation, and abandonment of societies\n\nGo to the site in the url and you can learn a lot of real information, not media hype about global warming.\n\nPS. The thermometer was only invented a few hundred years ago. No record of temperatures older than that exists. But old wood lasts for thousands of years and is a true account of local conditions. \n\nEnjoy! It is a fascinating science.
181649
what statistical informations can be extracted from difference between actual and estimate data?and how?
213634
you can probably research all three sources, and give an approximation,  YOU MAY BE ABLE TO ASK THIS QUESTION UNDER GEOLOGY, OR EVEN PALEONTOLOGY, but when you research stay away from evolutionary theory