History of the Earth A matter-of-time scale… If the age of the Earth (4.6 billion years) were condensed into one year ... Jan. 1… Earth was born Early Feb… Oldest known rocks formed Late Mar… First primitive life formed Mid-Nov... First complex life with shells or skeletons formed Late-Nov… First land animals Dec 25… Extinction of the dinosaurs Dec 31… Humans evolved in the evening Dec 31… One second before midnight, humans first set foot on the Moon
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History of the Earth A matter-of-time scale… If the age of the Earth (4.6 billion years) were condensed into one year... Jan. 1…Earth was born Early Feb…Oldest.
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History of the EarthA matter-of-time scale…
If the age of the Earth (4.6 billion years) were condensed into one year ...
Jan. 1… Earth was born Early Feb… Oldest known rocks formed Late Mar…First primitive life formed Mid-Nov... First complex life with shells or skeletons formed Late-Nov… First land animals Dec 25… Extinction of the dinosaurs Dec 31… Humans evolved in the evening Dec 31… One second before midnight, humans first set foot on the Moon
BIGBIG Ideas: Ideas:1. Scientists use several methods to
learn about Earth’s long history.2. The oceans and atmosphere formed
and life began during the three eons of the Precambrian, which spans nearly 90% of Earth’s history.
3. Complex life developed and diversified during the three eras of the Phanerozoic as the continents moved into their present positions.
HOW have scientists investigated and understood the history of Earth and the ages of rocks?
By studying rocks and fossils…
Uniformitarianism:
geologic processes occurring today have been occurring since Earth formed
the present is the key to the past
I. Determining Relative Age
Relative Age:The age of a rock or an event as
compared with some other rock or event
A comparison (older vs. younger); does NOT indicate an exact age
Principle of Original Horizontality: most sedimentary layers of rock are deposited in a horizontal position
A. Law of Superposition: an undeformed sedimentary rock layer is older than the one above it and younger than the layer below it.
How would you explain this?
B. B. Unconformities:Unconformities:breaks in the geologic record
An UNCONFORMITY is…a GAP in the sedimentary rock record (like missing