"Deep time" by Ariadne Unst

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Evolution notes.

"Deep time" describes geological time scales.

• Introduced by John McPhee (Basin and Range) to describe geological time scales.

• Eras of geological time.

• McPhee: "On the geological time scale, a human lifetime is reduced to a brevity that is too inhibiting to think about deep time. ... Geologists ... see the unbelievable swiftness with which one evolving species on the Earth has learned to reach into the dirt of some tropical island and fling 747s across the sky ... Seeing a race unaware of its own instantaneousness in time, they can reel off all the species that have come and gone, with emphasis on those that have specialized themselves to death."

• David Brower (Friends of the Earth founder) compares geological time to the six days of creation in the Genesis story: On the 6th day about:
  • 4 p.m., big reptiles appear.
  • 9 p.m., redwoods appear; big reptiles are gone.
  • 11:57 p.m., humankind appears.
  • 11:59:45 p.m., Jesus born.
  • A fortieth of a second before midnight, Industrial Revolution begins.
  McPhee quote Brower: "We are surrounded with people who think that what we have been doing for one fortieth of the [last] second can go on indefinitely. They are considered normal, but they are stark raving mad."

• Also see McPhee's 1999 Pulitzer-winning Annals of the Former World.

Eras of geological time

This table based in part on data published by John McPhee in Wild Earth (Summer 2002).

Cenozoic Era (65 MYA to today)	Quaternary (1.8 MYA to today) Holocene (11 KYA to today) Pleistocene (1.8 MYA to 11 KYA) (18 KYA = maximum extent of glaciers in North America) Tertiary (65 MYA to 1.8 MYA) Pliocene (5 MYA to 1.8 MYA) "more recent"; almost half of its mollusks have survived extinction; includes 4 pulses of glaciation. Miocene (23 MYA to 5 MYA) "moderately recent"; 15% of its mollusk species have survived extinction. Oligocene (38 MYA to 23 MYA) "but a little recent". Eocene (54 MYA to 38 MYA) "dawn of the recent"; under 4% of its mollusk species have survived extinction. Paleocene (65 MYA to 38 MYA) "old recent".
Mesozoic Era (245 MYA to 65 MYA)	Cretaceous (146 MYA to 65 MYA) e.g. opossum. Jurassic (208 MYA to 146 MYA) Triassic (245 MYA to 208 MYA) e.g. oysters.
Paleozoic Era (544 MYA to 245 MYA)	Permian (286 MYA to 245 MYA) Carboniferous (360 MYA to 286 MYA) Pennsylvanian (325 MYA to 286 MYA) Mississippian (360 MYA to 325 MYA) Devonian (410 MYA to 360 MYA) e.g. some clams. Silurian (440 MYA to 410 MYA) Ordovician (505 MYA to 440 MYA) Cambrian (554 MYA to 505 MYA)
Precambrian Time (4500 MYA to 544 MYA)	(second 2 billion years) Aerobic life appeared, probably in Helikan or Hadrynian times. Archean Eon (first 2 billion years) Photosynthesis began in the middle Archean

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Copyright © 2006 by Ariadne Unst.