Geologic Terms
Period of mountain building in which tectonic forces cause rocks to be faulted, folded and/or metamorphosed
Orogeny
Ancient cores of continents made of Precambrian igneous & metamorphic rocks
Shield
Empty cavity formed when the hard parts of a buried organism are dissolved/reacted away
Mold
Indirect evidence for ancient life such as footprints, trails or burrows
Trace Fossil
Study of tree rings to calculate dates of past events and to determine climatic changes in the past
Dendrochronology
Alternating bands of light- and dark-colored sediments deposited respectively during summer and winter in large lakes
Varves
Era of “Ancient Life”
Paleozoic
Era of “Middle Life”
Mesozoic
Era of “Recent Life”
Cenozoic
Eon of “Visible Life”; Eon of multicellular organisms with hard parts
Phanerozoic
Eon of one-celled organisms
Proterozoic
Eon of “Ancient” Time
Archean
Eon of “Hellish” Time
Hadean
Chart used to describe earth’s history by dividing it into various eons, eras, periods & epochs, originally based only on the fossil record
Geologic Time Scale
A 3-D copy of the hard parts of an organism formed when the hard parts of a buried organism are dissolved/reacted away and the resulting cavity is filled with sediments
Cast
The most common Precambrian fossils (of algae) found in numerous places around the world and dating back hundreds of millions to billions of years
Stromatolites
When many types of living things (species) disappear from earth at the same time
Mass extinction
Change in living things through time
Evolution
Scientist that studies fossils and ancient organisms
Paleontologist
Turned to stone; fossilized in rock
Petrified
In undisturbed sedimentary rocks, the oldest rocks are on the bottom and the youngest are on the top
Principle of Superposition
Younger features cut across or through older features
Principle of Cross-Cutting Relationships
Rocks metamorphosed by the magma are older than the intrusion or lava flow, unmetamorphosed rocks are younger than the lava flow
Principle of Contact Metamorphism
Fossils and the rocks they are found in can be arranged in a definite order according to their age
Principle of Fossil Succession
Sediments are deposited in originally flat layers
Principle of Original Horizontality
Isotope formed from the decay of an unstable isotope
Daughter Isotope
Fundamental principle of geology that states the processes which occur on Earth today are the same processes that occurred in the past; the present is the key to the past
Uniformitarianism
Matching a rock layer or rock unit in one place with the same rock layer in another place using rock type, thickness, fossils, ect.
Correlation
Any break in the rock record when erosion took place instead of deposition
Unconformity
The age of a rock formation or event compared to the surrounding rock formations or events
Relative Date
Remains or traces of ancient life
Fossils
Fossils that are widespread over a large area of earth and only existed for a short amount of time and are used to give approximate numerical dates to rock formations and geologic events
Index Fossils
The absolute age of a rock or mineral calculated using the ratios of parent and daughter isotopes
Radiometric Date
Date that gives the number of years that have passed since a rock formed or an event occurred
Absolute Date
The spontaneous breaking apart of nuclei of atoms through time to form new & different atoms
Radioactive Decay
An unstable isotope that has not yet decayed
Parent Isotope
The time it takes half the atoms of a parent isotope to decay into atoms of the daughter isotope.
Half life
Atoms that have the same number of protons, but different numbers of neutrons
Isotope
The largest time expanse in geologic time consisting of 100s of millions of years
Eon
The smallest time expanse in geologic time consisting of millions of years
Epoch
The second largest time expanse in geologic time consisting of many tens of millions of years
Era
The second smallest time expanse in geologic time consisting of tens of millions of years
Period
Period of mountain building in which tectonic forces cause rocks to be faulted, folded and/or metamorphosed
Orogeny
Ancient cores of continents made of Precambrian igneous & metamorphic rocks
Shield
Empty cavity formed when the hard parts of a buried organism are dissolved/reacted away
Mold
Indirect evidence for ancient life such as footprints, trails or burrows
Trace Fossil
Study of tree rings to calculate dates of past events and to determine climatic changes in the past
Dendrochronology
Alternating bands of light- and dark-colored sediments deposited respectively during summer and winter in large lakes
Varves
Era of “Ancient Life”
Paleozoic
Era of “Middle Life”
Mesozoic
Era of “Recent Life”
Cenozoic
Eon of “Visible Life”; Eon of multicellular organisms with hard parts
Phanerozoic
Eon of one-celled organisms
Proterozoic
Eon of “Ancient” Time
Archean
Eon of “Hellish” Time
Hadean
Chart used to describe earth’s history by dividing it into various eons, eras, periods & epochs, originally based only on the fossil record
Geologic Time Scale
A 3-D copy of the hard parts of an organism formed when the hard parts of a buried organism are dissolved/reacted away and the resulting cavity is filled with sediments
Cast
The most common Precambrian fossils (of algae) found in numerous places around the world and dating back hundreds of millions to billions of years
Stromatolites
When many types of living things (species) disappear from earth at the same time
Mass extinction
Change in living things through time
Evolution
Scientist that studies fossils and ancient organisms
Paleontologist
Turned to stone; fossilized in rock
Petrified
In undisturbed sedimentary rocks, the oldest rocks are on the bottom and the youngest are on the top
Principle of Superposition
Younger features cut across or through older features
Principle of Cross-Cutting Relationships
Rocks metamorphosed by the magma are older than the intrusion or lava flow, unmetamorphosed rocks are younger than the lava flow
Principle of Contact Metamorphism
Fossils and the rocks they are found in can be arranged in a definite order according to their age
Principle of Fossil Succession
Sediments are deposited in originally flat layers
Principle of Original Horizontality
Isotope formed from the decay of an unstable isotope
Daughter Isotope
Fundamental principle of geology that states the processes which occur on Earth today are the same processes that occurred in the past; the present is the key to the past
Uniformitarianism
Matching a rock layer or rock unit in one place with the same rock layer in another place using rock type, thickness, fossils, ect.
Correlation
Any break in the rock record when erosion took place instead of deposition
Unconformity
The age of a rock formation or event compared to the surrounding rock formations or events
Relative Date
Remains or traces of ancient life
Fossils
Fossils that are widespread over a large area of earth and only existed for a short amount of time and are used to give approximate numerical dates to rock formations and geologic events
Index Fossils
The absolute age of a rock or mineral calculated using the ratios of parent and daughter isotopes
Radiometric Date
Date that gives the number of years that have passed since a rock formed or an event occurred
Absolute Date
The spontaneous breaking apart of nuclei of atoms through time to form new & different atoms
Radioactive Decay
An unstable isotope that has not yet decayed
Parent Isotope
The time it takes half the atoms of a parent isotope to decay into atoms of the daughter isotope.
Half life
Atoms that have the same number of protons, but different numbers of neutrons
Isotope
The largest time expanse in geologic time consisting of 100s of millions of years
Eon
The smallest time expanse in geologic time consisting of millions of years
Epoch
The second largest time expanse in geologic time consisting of many tens of millions of years
Era
The second smallest time expanse in geologic time consisting of tens of millions of years
Period