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This text provides an overview of key concepts in Earth's natural history, including the geologic time scale, plate tectonics, extinction events, dominant species, and the role of cyanobacteria and the ozone layer. It also discusses fossilization, continental drift, and the significance of index fossils. A helpful resource for studying Earth's history.
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Scientists use the geologic time scale to divide Earth’s natural history into smaller pieces. • The theory of plate tectonics help explain how tectonic plates move. • All the dinosaurs died-out during the Cretaceous-Tertiary extinction.
Mammals have been the dominate animal in the Cenozoic Era. • Cyanobacteria help form Earth’s oceans and air by releasing oxygen gas. • The largest division of geologic time is an eon.
Tectonic plates move thousands of miles over geologic time, but only between 2cm and 5cm per year.
Science Fair is February 7,2018 • Armadillos came to North America from South America across the Panama Land Bridge. • Fossilized organisms in younger rock layers are younger than fossilized organisms in older rock layers. • The fossil record is incomplete because most organisms never became fossils.
The trace or remains of an organism that lived long ago is called a fossil. • The formation of the ozone layer allow life to survive on land by absorbing harmful radiation from the sun.
The Phanerozoic Eon is further divided into three eras. • Tectonic plates move around Earth, carrying continents along with them, in a process called continental drift. • Life first appeared on Earth 3.6 billion years ago.
Minerals replace the pore spaces in an organism’s hard tissue during the process of petrification. • Earthquakes are caused along the San Andreas fault by the horizontal movement of tectonic plates along a transform boundary.
Marine fossils discovered on tops of mountains in Canada tell scientists that the mountains were once below sea level. • Fossils of freshwater organisms found in Antarctica show that Antarctica used to be warmer.
At La Brea, for the past 38,000 years, many organisms have been preserved in thick, sticky pools of asphalt. • Mesosaurus fossils found in South America and southwestern Africa show that the continents were once joined.
Fossils of organisms that lived during a short, well-defined geologic time span that are plentiful, and are found throughout the world are called index fossils. • Preserved footprints are an example of a trace fossil.
