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Geologic Time

Earth History

Absolute Age a more specific age for a rock, mineral, or other object; done with carbon
Cast a fossil that is a solid copy of an organism's shape
Cenozoic Era a.k.a "Age of Mammals" era that began about 66 million years ago and is the time in Earth's we live in now;
Continental Drift Theory gradual shifting of Earth's plates causing continents to change their global positions over time (Pangea)
Deposition process in which sediment is laid down in new locations
Era a unit of geologic time that includes two or more periods; we have 3 of them; divided by mass extinctions
Erosion the process by which water, ice, wind, or gravity moves weathered rock or soil
Evolution the change in population of a species over time
Extinct describes organisms that no longer exist anywhere on Earth; Happens because species cannot adapt to environmental changes
Extrusion an igneous rock layer formed when lava flows on surface layers of rock and hardens
Fault a break in the Earth's crust
Fossil evidence of past life preserved in rock
Fossil record the complete body of fossils that shows how species and ecosystems change over time
Geologic Time Scale a record of all biological and geological evolution (changes over time)
Half-life the time needed for half of a sample of radioactive substance to undergo radioactive decay
Index fossil a fossil found in a narrow time range but widely distributed around the earth; used to date rock layers
Isotope an atom that has the same number of protons as other atoms of the same element do BUT has a different number of neutrons
Intrusion an igneous rock layer when magma hardens below the Earth's surface
Law of Superposition says that the oldest rocks lie on the bottom and the youngest rocks are on top of any undisturbed sequence of sedimentary rocks.
Mass extinction occurs when a large amount of the living things go extinct in a relatively short period of time.
Mesozoic Era a.k.a. "Age of the Reptiles or Dinosaurs" era that began 245 million years ago
Mold a fossil that is formed when an organism is buried in sediment
Paleontologist a scientist that studies fossils to learn about organisms that lived long ago
Paleozoic Era a.k.a. "Age of the Fishes" time in history when organisms with spines appeared (vertebrates: fish, insects, and small reptiles) era that began about 544 million years ago and lasted for almost 300 million years
Period a subdivision of the eras in geologic time; divided by different rock types
Precambrian Time covers about 88% of the Earth's history, bacteria came first and soft multicellular organisms arrived toward the end
Radioactive dating the process by which the age of a rock is determined by measuring the amount of radioactive isotopes present in the rock or rock sample
Radioactive decay when elements break down over time and release particles and energy
Relative age the age of an object compared to the ages of rock layers or fossils near it; used w/ Law of Superposition; an estimation of age
Trace fossil a fossilized mark that is formed in soft sediment by the movement or actions of an animal (ex. footprint)
Trilobite an index fossil that looks like a cockroach
Unconformity a gap in the geologic record; usually caused by erosion, flood, earthquake or other natural causes
Petrified fossil a type of fossil where minerals replace all or part of the organism
Preserved remains remains that are preserved because organisms become trapped in amber, tar, snow
Carbon film an extremely thin coating of carbon on the rock in the shape of a past organism
Carbon-14 dating All plants and animals contain some amount of carbon-14. As long as the organism is alive, the amount of carbon-14 stays the same. After an organism dies, then no more carbon is added and the carbon-14 in the organism's body starts radioactive decay.
Igneous rock rock that forms when magma cools and solidifies
Metamorphic rock rock that has been changed by heat and pressure
Sedimentary rock a rock that forms from compressed or cemented layers of sediment
Law of Horizontality states that sediments settle down in horizontal layers
Law of Uniformitarianism the idea that the same processes we see occurring now also occurred in the past
ice core A long cylinder of ice obtained from drilling through ice caps or ice sheets; used to study past climates.
Created by: jhandy8
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