Earth's History Flashcards
Uniformitarianism
The principle that most of the goelogic events of the past are similar to processes that we can observe in the present
Law of Superposition
The principle that the lowest layers in a sequence of rock strata must have been deposited before the layers above, unless the rocks have been turned upside down
Outcrop
bedrock that is exposed at the surface because it is not covered by soil
Orogeny
the process of mountiain building
Extrusion
Molten, liquid rock (lava) flowing out onto the surface of the earth. (fine grained igneous rock)
Intrusion
molten, liquid rock (magma) being pushed into cracks within the earth. (coarse grained igneous rock)
Lava
molten rock at the surface of the earth
folded strata
layers of rock that have been bent by forces within the Earth
Fault
a break in the rock of the Earth’s crust along which there has been displacement
Uplift
The rising of the Earth’s crust from forces within the Earth, generally related to motions of the tectonic plates
Joint
a crack in a rock produced by shrinking or uneven pressure. (no displacement happens).
Fossil
Any preserved remains or traces of life
Species
a group of living organisms with similar characteristics, a common name, can reproduce
Correlation
A matchup of rock layers in different locations by age or rock types
Index Fossil
A fossil that can be found over a large geographic area but existed for a brief period of geologic time
Organic Evolution
The principle that living things have changed in form through the history of the Earth from a few simple organisms to a great diversity of organisms
Dendritec
a pattern resembling tree branches
Unconformity
a gap in the geologic record caused by the erosion of sediments or rock before they are protected by layers above
Absolute Age
The age of a rock unit, a fossil, or an event expressed in units of time, such as years
Relative Age
Age expressed as before or after other events without specifying the age in units of measure. a comparative age
Radioactivity
The emission of energy rays or nuclear particles from the breakdown of an unstable isotope
Radiative Balance
Equilibrium between absorbed radiant energy and radiant energy given off
Isotope
a form of an element with more or fewer neutrons than other forms of the same element
Decay product
The element produced by the decay of a radioactive isotope
Half-Life
The time required for half of a radioactive element’s atoms in a sample to change to the decay product
Decay-Product Ratio
The ratio between the mass of a radioactive element and its decay product
Carbon 14
a radioactive form of the element carbon that has been used to find the absolute age of recent fossils and geologic events
Reversed Magnetic Polarity
An igneous rock that was formed at a time in the geologic past when the north and south magnetic poles of the Earth had opposite polarity that they have at the present
Geologic Time Scale
Division of the history of the Earth originally based upon observations of fossil evidence
Era
a large division of geologic time
Period
In geologic time, a subdivision of an era
Event
A change or series of changes in the Earth’s environment
Time
a measurable period in which an event or process occurs
Pangaea
The ancient supercontinent that broke apart millions of years ago to form the present continents
Ice Age
A long period of Earth’s history when ice sheets cover large areas of the continents.
