why is it difficult to determine the absolute age of a sedimentary rock?
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It can be difficult to determine the absolute age of a rock. ... Deposition slowly builds layer upon layer of sedimentary rock. But some of these layers may erode away, exposing an older rock surface. Then deposition begins again, building new rock layers.
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['475 MILLION YEARS AGO.', '362 MYA.', '290 MYA.', '130 MYA.']
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Today's knowledge of fossil ages comes primarily from radiometric dating, also known as radioactive dating. Radiometric dating relies on the properties of isotopes. These are chemical elements, like carbon or uranium, that are identical except for one key feature -- the number of neutrons in their nucleus.
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['Precambrian Time: 4.6 billion to 542 Million Years Ago. John Cancalosi / Getty Images. ... ', 'Paleozoic Era: 542 Million to 250 Million Years Ago. Jose A. ... ', 'Mesozoic Era: 250 Million to 65 Million Years Ago. Science Library / Getty Images. ... ', 'Cenozoic Era: 65 Million Years Ago to the Present.']
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Chemical sedimentary rocks are identified by identifying the mineral from which they are composed. In this lab there are four minerals that need to be identified - quartz, halite, gypsum and calcite. Quartz has a hardness of 7 and is very difficult to scratch, even with a good quality knife blade.
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The story of Joshua Tree's geology begins nearly two billion years ago, when Earth was about half its present age. As eroded sediments washed off ancient continents into the ocean, thick sediment layers accumulated in the waters offshore. Over time, the bottom layers were compressed and fused into sedimentary rock.
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Absolute dating. Geologists often need to know the age of material that they find. They use absolute dating methods, sometimes called numerical dating, to give rocks an actual date, or date range, in number of years. This is different to relative dating, which only puts geological events in time order.
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The deposited rocks build up in layers, called sediments . This process is called sedimentation. ... These processes eventually make a type of rock called sedimentary rock. It may take millions of years for sedimentary rocks to form.
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They contain fossils, the preserved remains of ancient plants and animals. ... Sedimentary rocks can contain fossils because, unlike most igneous and metamorphic rocks, they form at temperatures and pressures that do not destroy fossil remains.
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Sedimentary rock is classified into two groups based on how they form. They are clastic and chemical. Clastic sedimentary rock is formed as bits of weathered rock become cemented together. ... Chemical sedimentary rocks form when minerals that are dissolved in water become deposited as solids.
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Detrital sedimentary rocks are mainly classified by the size of their grain. ... If you have rock that contains grains larger than sand, you have conglomerate if it contains large rounded grains and breccia if it contains angular grains. Chemical sedimentary rocks are composed of mineral crystals that form out of solution.
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Answer and Explanation: Detrital sedimentary rocks are classified primarily on the basis of grain size, which is the size of the rock fragments that compose the sedimentary...
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The oldest rocks in the Zagros range date to Precambrian time (that is, before 541 million years ago), and the Paleozoic Era rocks that date to between 541 million and 252 million years ago are found at or near the highest peaks.
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They found that the half-life is just 68 million years, 30 per cent shorter than thought. That means that every rock dated by samarium-146 decay – which include some of the oldest on Earth and the moon, and even some Martian meteorites – formed 20 million to 80 million years earlier than thought.
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Sedimentary rocks are formed by sediment that is deposited over time, usually as layers at the bottom of lakes and oceans. This sediment can include minerals, small pieces of plants and other organic matter. The sediment is compressed over a long period of time before consolidating into solid layers of rock.
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Relative dating is used to determine a fossils approximate age by comparing it to similar rocks and fossils of known ages. Absolute dating is used to determine a precise age of a fossil by using radiometric dating to measure the decay of isotopes, either within the fossil or more often the rocks associated with it.
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Let's review. Radiometric dating is a method used to date rocks and other objects based on the known decay rate of radioactive isotopes. ... Radiocarbon dating is a method used to determine the age of organic material by measuring the radioactivity of its carbon content.