Lucy Mendez, 40 years old
The Age of Dinosaurs was so many millions of years ago that it is very difficult to date exactly. Scientists use two kinds of dating techniques to work out the age of rocks and fossils. The first method is called relative dating. This considers the positions of the different rocks in sequence in relation to each other and the different types of fossil that are found in them. The second method is called absolute dating and is done by analysing the relative dating dinosaurs of radioactive decay in the minerals of the rocks. Scientists find out the age of a dinosaur fossil by dating not only the rocks in which it lies, but those below and above it.
When paleontologist Mary Schweitzer found soft tissue in a Tyrannosaurus rex fossilher discovery raised an obvious question -- how the tissue could have survived so long? The bone was 68 million years old, and conventional wisdom about fossilization is that all soft tissue, from blood to brainsdecomposes. Only hard parts, like bones and teeth, can become fossils. But relative dating dinosaurs some people, the discovery raised a different question. How do scientists know the bones are really 68 million years old? Today's knowledge of fossil ages comes primarily from radiometric datingalso known as radioactive dating. Radiometric dating relies on the properties of isotopes.
Relative dating is used to arrange geological events, and the rocks they leave behind, in a sequence. The method of reading the order is called stratigraphy layers of rock are called strata. Relative dating does not provide actual numerical dates for the rocks.
Relative dating dinosaurs
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Relative fossil dating is different from absolute dating, in one important way: Absolute dating gives you a number for example, carbon dating a fossil to 50 million years ago. Relative dating puts the fossil in contextwhat lived before it, and what lived after. Relative dating relates fossils to events. These events may be paleontological relating to ancient life, like dinosaur extinction ; geographical relating to earth and natural environment, like eruptions and the Ice Age ; and archaeological relating to ancient society and structures, like the appearance of the Maya. Relative fossil dating of ancient species relies upon stratigraphy. This is the study of layers that make relative dating dinosaurs the Earth's crust.
The most widely known form of radiometric dating is carbon dating. This is what archaeologists use to determine the age of human-made artifacts. But carbon dating won't work on dinosaur bones. The half-life of carbon is only 5, years, relative dating dinosaurs carbon dating is only effective on samples that are less than 50, years old. Dinosaur bones, on the other hand, are millions of years old -- some fossils are billions of years old. To determine the ages of these specimens, scientists need an isotope with a very long half-life. Some of the isotopes used for this purpose are uranium, uranium and potassiumeach of which has a half-life of more than a million years. Unfortunately, these elements don't exist in dinosaur fossils themselves. Each of them typically exists in igneous rock, or rock made from cooled magma.
Relative dating is the science of determining the relative order of past events i. In geology, rock or superficial deposits , fossils and lithologies can be used to correlate one stratigraphic column with another. Prior to the discovery of radiometric dating in the early 20th century, which provided a means of absolute dating , archaeologists and geologists used relative dating to determine ages of materials. Though relative dating can only determine the sequential order in which a series of events occurred, not when they occurred, it remains a useful technique. Relative dating by biostratigraphy is the preferred method in paleontology and is, in some respects, more accurate. The regular order of the occurrence of fossils in rock layers was discovered around by William Smith. While digging the Somerset Coal Canal in southwest England, he found that fossils were always in the same order in the rock layers. As he continued his job as a surveyor , he found the same patterns across England.