Geologic Time and Earth's History Flashcards
Define absolute time.
The exact date and/or time that something happened
Define relative time.
The time that something happened relative to another day (two years ago, five days after, etc.)
Define uniformitarianism.
The theory that the Earth’s processes that are currently occurring have always been occurring throughout the universe
Define unconformity.
A gap in the rock record
Define nonconformity.
An unconformity between two very different rock types
Define disconformity.
A break in the rock record caused by erosion or non-deposition of sediment
Define radioactivity.
The act of an unstable atomic nucleus emitting radiation spontaneously
Define half-life.
The time that half of the atomic nuclei of a radioactive sample to decay
Define angular unconformity.
Tilted or folded sedimentary rocks overlain by more flat lying strata
Define fossil.
The remains or impressions of an organism preserved in petrified form as a mold or cast in rock
What are trilobites?
An extinct marine arthropod that occurred abundantly during the Paleozoic era
What are ammonites?
A group of extinct marine mollusc animals. Closer related to living coleoids than to nautiloids
What are cyanobacteria?
Microorganisms related to the bacteria that are capable of photosynthesis
What was Pangaea?
A supercontinent that existed during the late Paleozoic and early Mesozoic eras
What is the Paleozoic era?
The longest era in the Phanerozoic eon. Lasted from 541 to 251.902 million years ago
What is the Mesozoic era?
Also called the Age of Reptiles and the Age of Conifers. The era between the Paleozoic and Cenozoic eras. Lasted from 252 to 66 million years ago
What is the Cenozoic era?
The current and most recent of the three geologic eras of the Phanerozoic eon. Lasted from 66 million years ago to the current day. Means “new life”
Which rocks in a sequence would be the oldest?
The rock layer closest to the bottom are older than the ones on top. This is the rule of superposition
How old is the Earth?
The Earth is estimated to be 4.6 billion years old
What principles are used in relative dating?
The principles of superposition, original horizontality, original lateral continuity, cross-cutting relationships, unconformities, faunal succession, and inclusions
What are the tree types of unconformities?
- Angular: tilted or folded sedimentary rocks overlain by more flat lying strata
- Nonconformity: an unconformity between two very different rock types
- Disconformity: break in the rock record caused by erosion or non-deposition of sediment
What are the principles of radioactive decay?
The parent is the decaying isotope whereas the daughter is the decay product. The loss or gain of a neutron creates a daughter of the same element, a loss or gain of a proton creates a daughter of a new element
How is geologic time divided?
Geologic time goes epochs, periods, eras, and eons
What is the origin of the solar system?
The solar system formed about 4.5 billion years ago from a dense cloud of interstellar gas. Through the effects of gravity. The cloud collapsed and a solar nebula was formed
What was something that happened in the Precambrian era?
The first multi-celled organism appeared, a supercontinent named Robinia was formed, and the first oceans formed
What was something that happened in the Paleozoic era?
The Cambrian explosion occurred, land plants flourished, and invertebrates invaded the land
What was something that happened in the Mesozoic era?
The age of dinosaurs, Pangaea broke up, and gymnosperms dominated the land
What was something that happened in the Cenozoic era?
The age of mammals, angiosperms dominate the land, and humans appear in this era
