EARTH 7 Lecture Notes - Lecture 4: Mesozoic, Paleozoic, Deep Time
10/10/17
● Deep time: “…no vestige of a beginning, no prospect of an end.”
●Uniformitarianism: Present is key to past
● Lord Kelvin (1824-1907)
○ Earth can’t be older than 20-40 Ma
● Earth’s age
○ Radioactivity not discovered until 1896
○ First absolute ages published in 1907
○ Earth rocks/minerals, moon rocks, and meteorites all suggest that the Earth and
Solar system formed ~4.5 billion years ago
● The geological Timescale
○ Earth is 4.5 GA years old
○ Precambrian Eon 4.5 GA- 540 MA
○ Phanerozoic Eon 540 MA - Current
■ Paleozoic Era 540 MA - 250 MA
■ Mesozoic Era 250 MA - 65 MA
● Triassic Period 250 MA - 200 MA
● Jurassic Period 200 - 145 MA
● Cretaceous Period 145 MA - 65 MA
■ Cenozoic Era 65 MA - current
Document Summary
Deep time: no vestige of a beginning, no prospect of an end. Earth can"t be older than 20-40 ma. Earth rocks/minerals, moon rocks, and meteorites all suggest that the earth and. Paleozoic era 540 ma - 250 ma. Mesozoic era 250 ma - 65 ma. Triassic period 250 ma - 200 ma. Cretaceous period 145 ma - 65 ma. All atmospheric o2 comes from photosynthetic bacteria. Eukaryotes have chromosomes, a nucleus, and organelles. Eukaryotes only evolved after rise of o2. Cl. and mt. have inner membrane made by organelle, and outer membrane made by host cell. Cl. and mt. replicate independently of the host cell. Cannot be regenerated by cell if lost. When dna and rna of cl. and mt. are analyzed, they nest within the cyanobacteria (cl. ) and purple bacteria (mt. ) First (solid evidence of ) eukaryotes in fossil record. Acritarchs present at 1. 8 ga (or older?) diverse @ 1 ga.
