Standard 6
SC.7.E.6.3
Identify current methods for measuring the age of Earth and its parts, including the law of superposition and radioactive dating.
Identify current methods for measuring the age of Earth and its parts, including the law of superposition and radioactive dating.
Standard Summary: This standard asks us to list modern ways that scientists measure the age of the Earth. We also must know how radioactive dating and the law of superposition help us date the age of the Earth and its parts.
Vocabulary!
Radioactive (Radiometric) Dating: the process of determining the age of rocks from the decay of their radioactive isotopes
Law of Superposition: A principal that describes the observation that rocks form layers in predictable ways. Unless disturbed, rocks are deposited so that the newest rock is at the top and the oldest on the bottom.
Relative Dating: The process of determining a general age of rocks/soil layers by comparing it to previously dated layers.
Element: A pure substance or single type of atom. They can be found on the periodic table of elements.
Radioactive: When the nucleus of an unstable atom loses energy by emitting radiation.
Half-life: the time required for half of the unstable, radioactive atoms in a sample to undergo radioactive decay and lose their radioactivity
Strata: A layer of sedimentary rock or soil that has characteristics that set it apart from other layers in the same area
Index Fossils: Fossils of animal and plant species that lived a short amount of time and have a known period of existence. Because we know the dates of these organisms, we also can know the age of the rock strata they are found in.
Law of Superposition: A principal that describes the observation that rocks form layers in predictable ways. Unless disturbed, rocks are deposited so that the newest rock is at the top and the oldest on the bottom.
Relative Dating: The process of determining a general age of rocks/soil layers by comparing it to previously dated layers.
Element: A pure substance or single type of atom. They can be found on the periodic table of elements.
Radioactive: When the nucleus of an unstable atom loses energy by emitting radiation.
Half-life: the time required for half of the unstable, radioactive atoms in a sample to undergo radioactive decay and lose their radioactivity
Strata: A layer of sedimentary rock or soil that has characteristics that set it apart from other layers in the same area
Index Fossils: Fossils of animal and plant species that lived a short amount of time and have a known period of existence. Because we know the dates of these organisms, we also can know the age of the rock strata they are found in.
Notes!Through many different discoveries and methods we have determined the Earth to be approximately 4.6 billion years. In the early years of this new science, naturalists noticed that rocks were arranged in layers called "strata" that settled with the youngest layers on top and the oldest on bottom. This law was later called the Law of Superposition. Other evidence pointed to an older Earth. Charles Darwin's theory of evolution and the uncovering of fossils of unknown animals and plants showed that the Earth had to be older than previously thought at the time. This would account for the vast number of different species that would require enough time to evolve and colonize different parts of the world.
|
In the early 1900's the concept of radioactivity surfaced and offered a new and much more accurate way to date rocks. Radiometric dating is a method commonly used in modern times to help date rocks and fossils. New rocks and fossils contain a certain amount of radioactive isotopes. As these rocks age, the isotopes lose energy at a regular and predictable rate. When half of the once-radioactive isotopes have become stable (not radioactive), this is referred to as the half life. Scientists know what many common elements' half-lives are. They are then able to count the percent of unstable (parent) isotopes compared to the stable (daughter) isotopes and have a very accurate date as to when the rock or fossil formed or was deposited.
|
|
Review what you've learned by taking the quiz!
|