Unit 1 History of the Earth Vocabulary Asthenosphere: the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection occurs. Ammonite: an extinct group of marine mollusk closely related to living squids and octopus which where shelled like modern nautilus. The earliest ammonites appear during the Devonian, and the last species died out during the Cretaceous extinction event. Ammonites are excellent index fossils, and it is often possible to link the rock layer in which a particular species or genus is found to specific geologic time periods. Archean Eon: The Second geological eon in which the Earth’s crust cooled to a solid and continents formed. The Earth’s heat caused this eon to be much more geologically active. The atmosphere had almost no free oxygen and the first ocean formed. The very first life on earth forms in the oceans in the form of bacteria. The evidence is 3.5 billion year old stromatolite. Cenozoic Era: The most recent geological era spanning the last 65 million years. Generally associated with the rise of mammals and birds. Climate has become cooler and dryer and several ice ages have changed the earth. Continental crust: The least dense of the crust material mostly silicon and having less metals then oceanic crust. Continental An early theory explaining the movement of the continents based on fossil evidence, geologic evidence and cartographic patterns. This theory was eventually replaced with plate tectonics. Convection: the movement caused within a by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat. Convection current: a stream of fluid propelled by thermal convection. The driving force in plate tectonics, ocean currents and wind. Convergent boundary: Plate boundary where the plates are colliding usually produces folded mountains or volcanoes.
Unit 1 History of the Earth Vocabulary Asthenosphere: the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection occurs. Ammonite: an extinct group of marine mollusk closely related to living squids and octopus which where shelled like modern nautilus. The earliest ammonites appear during the Devonian, and the last species died out during the Cretaceous extinction event. Ammonites are excellent index fossils, and it is often possible to link the rock layer in which a particular species or genus is found to specific geologic time periods. Archean Eon: The Second geological eon in which the Earth’s crust cooled to a solid and continents formed. The Earth’s heat caused this eon to be much more geologically active. The atmosphere had almost no free oxygen and the first ocean formed. The very first life on earth forms in the oceans in the form of bacteria. The evidence is 3.5 billion year old stromatolite. Cenozoic Era: The most recent geological era spanning the last 65 million years. Generally associated with the rise of mammals and birds. Climate has become cooler and dryer and several ice ages have changed the earth. Continental crust: The least dense of the crust material mostly silicon and having less metals then oceanic crust. Continental An early theory explaining the movement of the continents based on fossil evidence, geologic evidence and cartographic patterns. This theory was eventually replaced with plate tectonics. Convection: the movement caused within a by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat. Convection current: a stream of fluid propelled by thermal convection. The driving force in plate tectonics, ocean currents and wind. Convergent boundary: Plate boundary where the plates are colliding usually produces folded mountains or volcanoes.
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