Earth and Space Science, Part 4
Question 1: Discuss the techniques of relative and absolute time.
Answer 1: A numerical, or “absolute,” age is a specific number of years, such as 150 million years ago. A “relative” age refers to a time range, such as the Mesozoic era. It is used to determine whether one rock formation is older or younger than another formation. Radioactive dating is a form of absolute dating and stratigraphy is a form of relative dating. Radioactive dating techniques have provided the most information about the absolute age of rocks and other geological features. Together, geochronologists have created a geologic time scale. Biostratigraphy uses plant and animal fossils within rock to determine its relative age.
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Question 2: Explain what fossils are and how they are formed.
Answer 2: Fossils are preservations of plants, animals, their remains, or their traces that date back to about 10,000 years ago. Fossils and where they are found in rock strata makes up the fossil record. Fossils are formed under a very specific set of conditions. The fossil must not be damaged by predators and scavengers after death, and the fossil must not decompose. Usually, this happens when the organism is quickly covered with sediment. This sediment builds up and molecules in the organism’s body are replaced by minerals. Fossils come in an array of sizes, from single-celled organisms to large dinosaurs.
Question 3: Discuss the type of information provided by fossils.
Answer 3: Fossils provide a wealth of information about the past, particularly about the flora and fauna that once occupied the Earth, but also about the geologic history of the Earth itself and how Earth and its inhabitants came to be. Some fossilized remains in the geohistorical record exemplify ongoing processes in the Earth’s environment, such as weathering, glaciation, and volcanism. These have all led to evolutionary changes in plants and animals. Other fossils support the theory that catastrophic events caused drastic changes in the Earth and its living creatures. One example of this type of theory is that a meteor struck the Earth and caused dinosaurs to become extinct. Both types of fossils provide scientists with a way to hypothesize whether these types of events will happen again.
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