Fossils And Geological History Flashcards
What is earths time scale?
The geological time scale is a record of the life forms and geological events in earths history.
What does the geological time scale provide?
Provides a system of chronologic measurement relating stratigraphy to time that is used by geologist, palaeontologist, and other earth scientists.
Used to describe the timing and relationship between events that have occurred during the history of earth
How did scientists develop the geological time scale?
By studying rock layers and fossils worldwide
Radioactive dating helped determine the absolute divisions in the time scale
How do geologists refer to this time scale?
Referring to time: early, middle, and late
Referring to rocks: lower, mid, and upper
What is the division of the geologic time scale?
Earths history is subdivided into time units based on the fossil record and extinctions
Name the divisions from largest to smallest
Eon (largest unit of geologic time)
Era (smaller division of an eon)
Period (smaller division of an era)
Epoch (smaller division of a period)
What are the four eons?
Pre-Archean or Hadean (4.6-3.8 Billion years)
Archean (3.8-2.5 Billion years)
Proterozoic (2.5 billion - 560 million years)
Phanerozoic (570 million years - present)
What does geologic time begin with?
Precambrian
What happened in the pre-archean or hadean eon?
~4.6 BYA: formation of earth and moon
~4 BYA: likely origin of life
What happened in ghetto Archean eon?
The eon of first life
~3.8 BYA: oldest known rocks
~3.5 BYA: oldest known fossils (singles celled organisms resembling bacteria)
3.2 BYA: first known plants (algae)
What happened in the Proterozoic eon?
The eon of first multi-celled life
1.2 BYA: first known animal (jellyfish)
What happened in the Phanerozoic eon?
The eon of complex life
What are the four eras?
Precambrian (88% of earths history)
Paleozoic (ancient life. 544 MYA. Lasted 300 million years)
Mesozoic (middle life. 240 MYA. Lasted 180 million years)
Cenozoic (recent life. 65 MYA. Continues through present day)
What geologic time are we living in?
The Holocene Epoch of the Quaternary Period of the Cenozoic Era
What era is the Paleozoic Era?
Ancient life (542 MYA - 250 MYA)
What are the 6 periods of the paleozoic era?
- Cambrian period
- Ordovician period
- Silurian period
- Devonian period
- Carboniferous period (Mississippian period and Pennsylvanian period)
- Permian period
What happened in the Cambrian period?
Age of the trilobites
What happened in the Ordovician period?
The only life on Earth was found in the seas. However, by the end of the Ordovician Period, life moved to land. Plants began to colonize out of the water paving the way in later periods for animals to follow