Unveiling Earth's Past: Fossils and Geological Clues
Explore the mysteries of Earth's past through fossils, rocks, and geological evidence. Learn how paleontologists decipher ancient life and environments, from unique preservation methods to the principles of catastrophism and uniformitarianism. Delve into the formation of fossils and the slow processes that shape our planet's history.
Download Presentation
Please find below an Image/Link to download the presentation.
The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author. Download presentation by click this link. If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.
E N D
Presentation Transcript
Clues to Earths Past Chapter 10
What You Should Know Already Fossils can be compared to one another and to living organisms according to their similarities and differences. Some organisms that lived long ago are similar to existing organisms, but some are quite different. Background Knowledge Atoms are made of a positive nucleus surrounded by negative electrons Some kinds of organisms that once lived on Earth have completely disappeared, although they were something like others that are alive today. 1. 2. 3.
Section 1: Fossils Key Points to Remember: Fossils include carbon films, molds, casts, and trace fossils Dead Organisms are more likely to become fossils if they have hard parts and are buried quickly after they die Paleontologists use clues from fossils to learn about ancient life and the environments ancient organisms lived in. Vocabulary to know: Fossil, catastrophism, uniformitarianism, carbon film, mold, cast, trace fossil, paleontologist
Fossils pg 326 Question Answer Are the insects in the amber alive? No, they died millions of years ago What are some other ways in which organisms can be preserved as fossils? Leaf imprints, petrified wood, dinosaur bones, or shells; these are all ways in which organisms can be preserved
Evidence of the Distant Past Rocks provide clues to Earth s past. Some of the most obvious clue that are present in rocks are fossils, the preserved remains or evidence of ancient living organisms. Some early scientists thought that fossils formed from the remains of organisms killed in disasters Catastrophism is the idea that conditions and organisms on Earth change because of quick, violent events.
Continued James Hutton proposed that changes on Earth take place very slowly. He proposed the principle of uniformitarianism. According to this principle, the same geologic process that occur today occurred in the past This principle says that most changes on Earth s surface occur in slow, continuous cycles In addition to the events explained by uniformitarianism, sometimes catastrophic events quickly change Earth s surface
Formation of Fossils An organism is more likely to become a fossil if it contains hard parts such as teeth or bones Fossils are more likely to form if an organism is buried quickly after it dies Tiny fossils are called microfossils
Types of Preservation If the actual organism becomes a fossil, it was completely enclosed over a long period of time to keep it away from air and bacteria Some fossils are called carbon films, which form when pressure drives off the gases and liquids from an organism s tissues, leaving only the carbon behind. Fossils also form when minerals in groundwater replace the tissues of dead organisms
Types continued Some fossils are molds, which is the impression in a rock left by an ancient organism When a mold fills with sediment or mineral deposits, it forms a fossil called a cast Trace fossils show evidence of the activity of ancient organisms, such as tracks or nests
Ancient Environments Paleontologist are scientists who study fossils Paleontologists compare fossils of ancient organisms with organism that live today. They use uniformitarianism to learn about the environments of ancient organisms If a fossil of an ancient organism is similar to an organism that lives today, these two organisms might have lived in a similar environment Fossils show that Earth s climate has changed many times in the past
Ancient Environments Fossils of plants such as ferns indicate that much of Earth was warm and humid 100 million years ago Fossils of some species such as the woolly mammoth help scientists learn about times that the climate of Earth was cool END OF SECTION Answer questions on page 334 #2, 4-8 Complete worksheet 14/16
Section 2: Relative-Age Dating Key Points to Remember Relative age dating is the age of rocks and geologic features compared with other rocks and features near by. The relative age of rock layers can be determined using geologic principles, such as the principle of superposition and the principle of inclusion Vocabulary: relative age, superposition, inclusion, unconformity, correlation, index fossil
Relative-Ages of Rocks Relative age is the age of rocks and geologic features compared to other rocks and features nearby The relative age of lower layers of rock is greater than the relative age of rocks above them. (meaning the rocks on the bottom are older than those on the top) The principle of superposition states that in undisturbed rock layers, the oldest rocks are on the bottom. According to the principle of original horizontality, most rock-forming material was deposited in horizontal layers
Relative ages of Rocks The principle of lateral continuity states that sediments are deposited in large, continuous sheets in all lateral directions. A piece of older rock that becomes part of a new rock is called an inclusion. The rock containing pieces of other rocks must be younger than the pieces. Sometimes, rock formations break, or fracture When rocks move along a fracture, the fracture is called a fault According to the principle of cross-cutting relationships, when a geologic feature cuts across another feature, the feature it cuts across is older.
Unconformities An unconformity is the surface between older, eroded rock and the younger rock on top of it Young sedimentary layers that form on top of older, horizontal sedimentary layers that have eroded create a disconformity Young sedimentary layers that form on top of older, tilted or folder sedimentary layers that have eroded create an angular unconformity. Young sedimentary layers that form on top of older metamorphic or igneous layers that have eroded create a nonconformity. Images on page 340
Correlation Matching rocks and fossils from different locations is called correlation. It helps scientists determine the geologic history of an area. Fossils are often used to learn the relative ages of rock layers that are far apart from each other. If two formations contain similar fossils, the formations are probably about the same age Fossils that are useful for determining relative age are from species that were abundant and existed for a short period of time in many different areas on Earth. Such fossils are known as index fossils. End of Section : Answer 1 & 2, 4, 7 & 8 from book Complete worksheet 26, 31, 34
Section 3: Absolute-Age Dating Key Points to Remember Absolute age is the age in years of a rock or object The radioactive decay of unstable isotopes occurs at a constant rate, measured as half-life. To date a rock or object, scientists measure the ratios of its parent and daughter isotopes Vocabulary: Absolute age, isotope, radioactive decay, half-life
Absolute Ages of Rocks The numerical age, in years, of any object is its absolute age Radioactivity can be used to help determine the absolute age of rocks Radioactivity is the release of energy from unstable atoms
Atoms An atom is the smallest part of an element that has the properties of that element. An atom contains protons (positive charge) and neutrons (neutral charge) in the nucleus. Atoms also have electrons (negative charge), which surround the nucleus. All atoms of the specific element contain the same number of protons Nuclei of atoms of the same element can contain different numbers of neutrons. Atoms of the same element that contain different number of neutrons called isotopes.
Atoms An isotope that does not change under normal conditions is said to be stable Isotopes that are not stable are radioactive isotopes During radioactive decay, an unstable element naturally changes into an element that is stable The element that undergoes radioactive decay is called the parent isotope. The element formed by radioactive decay is called the daughter isotope.
Atoms Different radioactive isotopes decay at different rates, but the decay rate is CONSTANT for each specific isotope For each radioactive isotope, the half-life is the time necessary for half of the parent isotopes to decay into daughter isotopes After two half-lives, one-fourth of the original parent isotopes remain
Radiometric Ages Radiocarbon dating uses isotopes of carbon-14 to determine the age of once-living organisms. As long as an organism lives, the amount of carbon-14 it contains is constant Radiocarbon dating involves comparing the amount of carbon-14 to the amount of carbon-12 in an organism that has died The half-life of carbon-14 is 5,730 years About 50,000 years after an organism has died, the carbon-14 has decayed so much that it cannot be measured.
Radiometric Ages Because carbon-14 is useful for only dating materials that are organic, it cannot be used to date rocks Radioactive isotopes are most likely to be trapped in igneous rocks, which means they can be dated by comparing numbers of parent and daughter isotopes Radioactive isotopes are not very useful in dating sedimentary rocks, because they are composed of grains of older rock. To date old rocks, scientists use radioactive isotopes with long half-lives The age of the oldest rocks on Earth put Earth s age at more than 4 billion years. END OF SECTION: Answer 1,2, 4 - 7, 9 from book Complete worksheet pg 51/56
