Dr. Kyle O. Eidahl

1. Geological Time Scale.
1. Presolar Era. (18–4.6 billion years?)
1. Origin of the Universe— 16 billion years?
2. Formation of Milky Way Galaxy— 12 billion years?
2. Formative Era. (4.6–3.6 billion years)
1. Formation of sun and planets— 4.6–4.5 billion years.
2. Heavy meteoritic cratering— 4 billion years.
3. Oldest rocks; crystals?— 3.8 billion years.
4. Condensation of atmospheric water into oceans— 3.8 billion years.
3. Archeozoic Era. (3.6–1.5 billion years)
1. Earliest fossils (algae)— 3.6–3 billion years.
2. Crustal and atmospheric evolution— 3–2.6 billion years.
3. Oxygen increasing in atmosphere— 2 billion years.
4. Oxygen producing microbes— 2 billion years.
4. Proterozoic Era. (1.5 billion–540 million years)
1. First macroscopic life forms; sexually reproducing life forms; growth of proto-continents— 1 billion years.
2. Small soft forms.
5. Paleozoic Era. (540–245 million years)
1. Cambrian Period. (540–500 million years)
1. Earliest abundant fossils (Trilobites)
2. Ordovician Period (500–440 million years)
1. Fishes— 500–450 million years.
2. Waxy coated algae begin to live on land— 430 million years.
3. Silurian Period. (440–410 million years)
1. Early land plants.
2. Millipedes evolve, the first land animal.
4. Devonian Period. (410–360 million years)
1. Appalachian mountains are formed via a plate tectonic.
2. Appearance of primitive sharks.
5. Mississippian Period. (360–325 million years)
1. Rise of amphibians— 350–300 million years.
2. Primitive insects.
6. Pennsylvanian Period. (325–290 million years)
1. Primitive ferns.
2. Rise of reptiles— 300–200 million years.
3. Winged insects.
7. Permian Period. (290–245 million years)
1. Permian Period mass extinction.
2. Conifers.
6. Mesozoic Era. (245-65 million years)
   1. Triassic Period (245–190 million years)
   1. First dinosaurs.
   2. Bees
   3. Pangaea starts to break apart.
   2. Jurassic Period (190–136 million years)
   1. Dominance of dinosaurs.
   2. First mammals and birds.
   3. Insects abundant.
   3. Cretaceous Period (136–65 million years)
   1. Dinosaurs dominant to end.
   2. Both marsupial and placental mammals appear.
   3. First flowering plants appear.
   4. Continents take present shape.
   5. Large meteorite impact at end of period?
7. Cenozoic Era (65 million years–Present)
1. Tertiary Period (Paleogene/Neocene) (65–1.8 million years)
1. Paleocene Epoch (65–54 million years)
1. Great development of primitive mammals.
2. Earliest known primate from this period.
3. Building of Rocky Mountains.
2. Eocene Epoch (54–38 million years)
1. Mammals consolidated their status as dominant land vertebrates.
3. Oligocene Epoch (38–23 million years)
1. Many older types of mammals became extinct.
2. First appearance of apes.
4. Miocene Epoch (23–5 million years)
1. Emergence of dogs, horses and human-like apes appeared.
5. Pliocene Epoch (5–1.8 million years)
1. Modern mammals became dominant.
2. Ape-like humans appeared in Africa.
2. Quaternary Period (1.8 million years–Present)
1. Pleistocene Epoch (1.8 million years–10,000 years)
1. Advance of Ice sheets in Northern Europe and North America.
2. Many giant mammals became extinct.
3. Early humans appear.
2. Holocene Epoch (10,000 years–Present)
1. Rising temperatures and retreat of ice sheets.