Dating methods in Archaeology. Are they accurate? | Ancient Origins
Sep 20, Unaware of the many fallacious assumptions used in the dating process, many people believe Carbon dating disproves the biblical timeline. Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in geochronology and archaeology. It is based on measurement of the. This dating method is based upon the decay of radioactive potassium to radioactive argon in minerals and rocks; potassium also decays. Potassium-argon dating, method of determining the time of origin of rocks by archaeology.
This isotope, which can be found in organic materials and can be used only to date organic materials, has been incorrectly used by many to make dating assumptions for non-organic material such as stone buildings. The half-life of 14C is approximately years, which is too short for this method to be used to date material millions of years old. The isotope of Potassium, which has a half-life of 1. Another absolute dating method is thermoluminescence, which dates the last time an item was heated.
It is the only method that can be used to date rocks, pottery and minerals for dates that are approximately between to 10, years old. This method is based on the fact that when a material is heated or exposed to sunlight, electrons are released and some of them are trapped inside the item.
This process frees energy in the form of light, which can be measured. Absolute dating supplies a numerical date whilst relative dating places events in time-sequence; both are scientifically useful.
How accurate are Carbon and other radioactive dating methods? • sheptonmallet.info
Radiometric Dating This is based upon the spontaneous breakdown or decay of atomic nuclei. Radioactive parent P atoms decay to stable daughter D atoms e. The time required for half the original number of parent atoms to decay is called the half life.
Some half-lives are listed below: The K-Ar method is often used for rock dating. This uses a simple exponential decay formula linking the original number, Po, of parent atoms in rocks and minerals to the P atoms now present, thereby enabling an estimate of geological age. Using radiometric techniques, the oldest dated minerals 4. One problem with earth dating is that the original earth surface is assumed to have eroded long ago.
But assuming the earth was formed at the time of the rest of our solar system, then recovered moon rock and meteorites can also be used to estimate the age of the earth. These estimates give 4. Non-radiometric Dating These techniques utilize the physical parameters of the earth, such as ice cores, annual lake sediments, and astronomical cycles.
Ice cores from Greenland and Antarctica show annual layers varves and can be traced up to about 40, years before the layers become too thin due to compaction. Similarly, annual lake sediments can be used to estimate relative age and conventional interpretation for the Green River varves suggests they have been formed over some 20 million years.
This implies the earth is at least 20 million years old. Astronomical cycles can also be used to measure relative age.
The earth precesses wobbles like a spinning top around the sun in a series of cycles. These cycles affect sunlight and hence long-term can form layers in rock.
In some cases these astronomical cycles in rock appear to have been laid down over some 25 million years and radiometric dating puts the absolute age of the rock at some million years. Dating Anomalies Here we outline a few dating methods or 'clocks' that present a dating anomaly when referenced to the widely accepted OE age of 4.
They appear to be inconsistent with an old earth. Radio Carbon C Dating At the outset we note C cannot be used to directly date the earth for the simple reason that the unstable C isotope has a half-life of just 5, years.
In other words, half of the radioactive isotope in a sample would have decayed to Nitrogen N in just 5, years. C dating of carbon-bearing materials is therefore limited to roughly 50, years. But YE scientists point out some anomalies in relation to C and a very old earth. For instance, measurable amounts of C have been found in fossil material, such as coal traditionally Carboniferous period c mya.
In fact, organic samples from every portion of the Phanerozoic record spanning the last million years on OE dating show detectable amounts of C The implication is that this organic material was either contaminated by new C, or it was buried much more recently and OE dating methods are suspect.How Old is that Rock?
Ocean Measurements One early approach was based upon ocean salinity [John Joly, 's]. This assumed the ocean was initially pure water and that it's salinity was derived from continental erosion. The technique gave 90 million years, but took no account of the non-constant erosion rate, or the loss and recycling of salt, or the fact that salt is obtained from other sources as well as continents.
More recently, work has been done on ocean sediments [S. Nevins, Institute for Creation Research]. This suggests that, given the current annual rates of erosion some Clearly, this seems incompatible with an ocean billions of years old.
However, this may be a simplistic computation since there is Sediment Recycling as sediments accumulate and cause continental plates to collide, resulting in land uplift and subsequent errosion. Earth's Magnetic Field The Earth's magnetic field is thought to arise from circulating electic currents in the Earth's molten metalic core, and scientists agree that the field is weakening. At the current rate of decline it could take just 1, years to disappear, with increasing effects upon the electronic systems of satellites and spacecraft.
Magnetic field decrease applies to other planets. For instance, recent satellite measurements show that Mercury's magnetic field is rapidly decaying and YE Creationists claim this indicates a young field. OE scientists believe that a weakened magnetic field could herald a new magnetic pole reversal. Magnetic pole reversals are rebutted by YE creationists.
Instead they claim that the field decrease can be used as a clock to date the earth since it has been decaying since the origin of the earth. Taking the half-life of the decaying magnetic moment at yearsthe field is now only about one third as strong as it was at the time of Christ. Working further back in time, the value of the earth's magnetic field approaches that of a magnetic star at 10, years ago.
Since this would need a huge nuclear power source, it seems magnetic field decay places an upper age limit on the earth of the order of 10, years. Whilst the rigour of this YE theory is disputed see talkoriginsrecent spacecraft observations have confirmed its planetary magnetic predicions made in !
Atmospheric Helium The decay of uranium and thorium isotopes results in a net build-up of Helium-4 atoms in the atmosphere. It is claimed to be increasing at an annual rate of 3. From these figures and known decay rates, it can be shown that the current amount of atmospheric Helium can be generated in just 11, years not billions of years. Short-Period Comets Short-period comets orbit the sun in less than years the Halley comet orbits about every 76 years.
However it is less useful for dating metal or other inorganic objects. Most rocks contain uranium, allowing uranium-lead and similar methods to date them. Other elements used for dating, such as rubidium, occur in some minerals but not others, restricting usefulness.
Dating methods in Archaeology. Are they accurate?
Carbon decays almost completely withinyears of the organism dying, and many fossils and rock strata are hundreds of times older than that. To date older fossils, other methods are used, such as potassium-argon or argon-argon dating. Other forms of dating based on reactive minerals like rubidium or potassium can date older finds including fossils, but have the limitation that it is easy for ions to move into rocks post-formation so that care must be taken to consider geology and other factors.
Radiometric dating and YEC[ edit ] See the main article on this topic: Young Earth creationism Radiometric dating — through processes similar to those outlined in the example problem above — frequently reveals that rocks, fossilsetc.
The oldest rock so far dated is a zircon crystal that formed 4.