Lisle Oct 27, Geology , Origins , Physics. We are told that scientists use a technique called radiometric dating to measure the age of rocks. We are also told that this method very reliably and consistently yields ages of millions to billions of years, thereby establishing beyond question that the earth is immensely old - a concept known as deep time. This apparently contradicts the biblical record in which we read that God created in six days, with Adam being made on the sixth day. From the listed genealogies, the creation of the universe happened about years ago. Has science therefore disproved the Bible?
Radiometric dating is a means of determining the age of very old objects, including the Earth itself. Radiometric dating depends on the decay of isotopes, which are different forms of the same element that include the same number of protons but different numbers of neutrons in their atoms. This geology science project will guide you through the process of radiometric dating, enabling you to explore and fill in the blanks. It explains how to .
Is this radioactive decay formula intimidating? If so, try not to worry: This science project will only use its graphical representation, known as the decay curve.
Radiometric dating science
Coming back to our example, Figure 4 shows the decay curve for the potassium K isotope. Can you figure out that the half-life time of K is 1. How long before all of the K parent isotopes decay? Graph showing the decay curve of potassium k with fraction remaining and time in billions of years.
One-half of the sample remains after 1. One-quarter of the sample remains after 2. And one-eighth of the sample remains after 3. Does this still seem a bit abstract?
This geology science project will guide you through the process of radiometric dating, enabling you to explore and fill in the blanks. It explains how to create a model of radioactive decay using dice. The model will behave the same way as isotopes in nature in important ways. You will create a decay curve for your hypothetical rare isotope, and use it to estimate the time since formation of hypothetical samples created by a friend.
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Our top priority is student learning. If you have any comments positive or negative related to purchases you've made for science projects from recommendations on our site, please let us know. Write to us at scibuddy sciencebuddies. In this part of the science project, you will make a model to explore radiometric dating.
The model uses six-sided dice, where each die represents one isotope in a radioactive sample used for dating. You will roll the dice to represent one unit of time passing, during which the parent isotopes have a chance to decay into the daughter isotopes. How much of a chance? Or, in other words, what is the probability of decay? One in six! You will put a sticker on one side of the dice and if a die lands with the sticker facing up, this will represent that isotope decaying into the daughter isotope.
If the sticker is not facing up, it means that the isotope has not decayed yet, so further rolls of the dice will decide when this parent isotope decays. You will collect the daughter isotopes in a separate bag so they can no longer decay and only use the remaining parent isotopes in the following roll. Table 1 lists the relation between model and real life.
In this part of the science project, you will create a graph of the decay curve of your isotope and use your curve to determine the half-life time of your isotope.
Remember, the half-life time of an isotope is the time it takes for half of the initial amount of isotopes to decay. You will then compare the half-life time you obtained using your data to the predicted half-life time using probability.
How close will your half-life time be to the calculated one? It this section, you will ask a volunteer partner to roll the six-sided dice, simulating the decay of isotopes in your sample just as you did to collect data for the decay curve.
Your partner decides after how many rolls of the dice he or she would like to stop. Your partner will hand you over the bag of daughter isotopes and the pot of parent isotopes when they have finished.
Your task is to use the sample bag with the daughter isotopes and pot with the parent isotopes and then estimate the number of times your partner rolled the dice or the elapsed time of your sample. If radioactive decay processes intrigue you, the following two project ideas might grab your attention:. Try one of our science activities for quick, anytime science explorations. The perfect thing to liven up a rainy day, school vacation, or moment of boredom.
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Science Buddies Staff. Accessed 11 May How Old Is That Rock? Introduction As humans, it seems easy for us to keep track of time lapses, as long as they range from a couple of seconds to a number of years.
Figure 1. Representation of an atom with its nucleus and an electron cloud around it. Note that, in this drawing, the nucleus is shown disproportionately large. Figure 2. Periodic table showing elements with their atomic symbol and atomic numbers. Figure 3.
Oct 27, "Science has proved that the earth is billion years old." We have all heard this claim. We are told that scientists use a technique called radiometric dating to measure the age of rocks. We are also told that this method very reliably and consistently yields ages of millions to billions of years, thereby establishing beyond question that the earth is immensely old - a . Understand that nobody is saying radiometric dating works perfectly in every conceivable set of circumstances; as with almost every tool in science, there are certain limitations to radiometric dating-and nobody understands these limitations better than the scientists who use these dating techniques. As they write on Talk Origins. For many people, radiometric dating might be the one scientific technique that most blatantly seems to challenge the Bible's record of recent creation. For this reason, ICR research has long focused on the science behind these dating techniques.
Representation of an aging rock. The radioactivity levels are indicated by wiggly arrows; green dots represent parent isotopes here, K and yellow dots represent daughter isotopes present in the rock at the indicated time after the formation of the rock. Figure 4. An example of the decay curve of potassium K This figure also illustrates how to use a decay curve to figure the time since formation, if the fraction of parent isotope remaining in the sample is known.
The red lines show how to obtain the half-life time, or the time after which half of the parent isotopes have decayed. The arrows indicate how to read the graph, starting from a fraction of parent isotope remaining via a horizontal line to a point on the curve, and then vertically down to a time on the time axis. Isotopes and Radioactivity Tutorial. Say a second friend who is aware of this arrangement visits and notices that your carton of ice cream contains 70 raisins and 10 chocolate chips.
She declares, "I guess you went shopping about three days ago. Because your roommate eats half of the chips on any given day, and not a fixed number, the carton must have held 20 chips the day before, 40 the day before that, and 80 the day before that. Calculations involving radioactive isotopes are more formal but follow the same basic principle: If you know the half-life of the radioactive element and can measure how much of each isotope is present, you can figure out the age of the fossil, rock or other entity it comes from.
Elements that have half-lives are said to obey a first-order decay process. They have what is known as a rate constant, usually denoted by k. The relationship between the number of atoms present at the start N 0the number present at the time of measurement N the elapsed time t, and the rate constant k can be written in two mathematically equivalent ways:. In addition, you may wish to know the activity A of a sample, typically measured in disintegrations per second or dps.
This is expressed simply as:. You don't need to know how these equations are derived, but you should be prepared to use them so solve problems involving radioactive isotopes. Scientists interested in figuring out the age of a fossil or rock analyze a sample to determine the ratio of a given radioactive element's daughter isotope or isotopes to its parent isotope in that sample.
With the element's decay rate, and hence its half-life, known in advance, calculating its age is straightforward.
Radiometric dating of rocks and minerals using naturally occurring, long-lived radioactive isotopes is troublesome for young-earth creationists because the techniques have provided overwhelming evidence of the antiquity of the earth and life. Radiocarbon Dating Mr. Andersen explains how carbon dating can be used to date ancient material. The half-life of radioactive carbon into nitrogen is also discussed. Earth sciences - Earth sciences - Radiometric dating: In , shortly after the discovery of radioactivity, the American chemist Bertram Boltwood suggested that lead is one of the disintegration products of uranium, in which case the older a uranium-bearing mineral the greater should be its proportional part of lead. Analyzing specimens whose relative geologic ages .
The trick is knowing which of the various common radioactive isotopes to look for. This in turn depends in the approximate expected age of the object because radioactive elements decay at enormously different rates. Also, not all objects to be dated will have each of the elements commonly used; you can only date items with a given dating technique if they include the needed compound or compounds. Uranium-lead U-Pb dating: Radioactive uranium comes in two forms, uranium and uranium The number refers to the number of protons plus neutrons.
Uranium's atomic number is 92, corresponding to its number of protons. The half-life of uranium is 4. Because these differ by a factor of almost seven recall that a billion is 1, times a millionit proves a "check" to make sure you're calculating the age of the rock or fossil properly, making this among the most precise radiometric dating methods. The long half-lives make this dating technique suitable for especially old materials, from about 1 million to 4. U-Pb dating is complex because of the two isotopes in play, but this property is also what makes it so precise.
The method is also technically challenging because lead can "leak" out of many types of rocks, sometimes making the calculations difficult or impossible. U-Pb dating is often used to date igneous volcanic rocks, which can be hard to do because of the lack of fossils; metamorphic rocks; and very old rocks. All of these are hard to date with the other methods described here.
Rubidium-strontium Rb-Sr dating: Radioactive rubidium decays into strontium with a half -life of Advanced analytic chemical equipment has revolutionized the understanding of the composition of rocks and minerals.
For example, the XRF X-Ray Fluorescence spectrometer can quantify the major and trace element abundances of many chemical elements in a rock sample down to parts-per-million concentrations. This geochemical method has been used to differentiate successive stages of igneous rocks in the plate-tectonic cycle.
The metamorphic petrologist can use the bulk composition of a recrystallized rock to define the structure of the original rock, assuming that no structural change has occurred during the metamorphic process. Next, the electron microprobe bombards a thin microscopic slice of a mineral in a sample with a beam of electrons, which can determine the chemical composition of the mineral almost instantly.
This method has wide applications in, for example, the fields of industrial mineralogymaterials scienceigneous geochemistryand metamorphic petrology. Microscopic fossils, such as ostracods, foraminifera, and pollen grains, are common in sediments of the Mesozoic and Cenozoic eras from about million years ago to the present. Because the rock chips brought up in oil wells are so small, a high-resolution instrument known as a scanning electron microscope had to be developed to study the microfossils.
The classification of microfossils of organisms that lived within relatively short time spans has enabled Mesozoic-Cenozoic sediments to be subdivided in remarkable detail. This technique also has had a major impact on the study of Precambrian life i. Carbonaceous spheroids and filaments about millimetres 0.
Earthquake study was institutionalized in with the formation of the Seismological Society of Japan under the leadership of the English geologist John Milne.
Milne and his associates invented the first accurate seismographs, including the instrument later known as the Milne seismograph. From studies of the Croatian quake of Oct. Today there are more than 1, seismograph stations around the world, and their data are used to compile seismicity maps. These maps show that earthquake epicentres are aligned in narrow, continuous belts along the boundaries of lithospheric plates see below. The earthquake foci outline the mid-oceanic ridges in the Atlantic, Pacific, and Indian oceans where the plates separate, while around the margins of the Pacific where the plates converge, they lie in a dipping plane, or Benioff zone, that defines the position of the subducting plate boundary to depths of about kilometres.
Sinceadditional information on the crust has been obtained from the analysis of artificial tremors produced by chemical explosions. These studies have shown that the Moho is present under all continents at an average depth of 35 kilometres and that the crust above it thickens under young mountain ranges to depths of 70 kilometres in the Andes and the Himalayas. This is seismic reflection profiling, the main method of exploration used by the petroleum industry.
During the late s a new technique for generating seismic waves was invented: thumping and vibrating the surface of the ground with a gas-propelled piston from a large truck. Earth sciences.