Earth's Eons and Eras: A Geological Timeline

Hadean Eon: 4500-4000 Million Years Ago

Geology:

• Intense volcanic activity
• Intense meteorite activity
• Moon formation
• First solid crust
• Formation of mantle and core

Climate:

• Atmosphere formation
• Hydrosphere formation

Archean Eon: 4000-2500 Million Years Ago

Geology:

• First microcontinents (plate tectonics)

Biosphere:

• First prokaryotic cells (bacteria and archaea)

Proterozoic Eon: 2500-541 Million Years Ago

Geology:

• First supercontinent (Rodinia)
• Active tectonic activity

Climate:

• Extreme climates (interior of Rodinia)
• Major glaciation at the end - "Snowball Earth"

Biosphere:

• First eukaryotic cells
• First cyanobacteria - photosynthesis - O2 production
• First multicellular organisms

Phanerozoic Eon: 541 Million Years Ago - Present

Paleozoic Era (541-252 Million Years Ago)

• Cambrian Period (541-485 Million Years Ago): Arthropods (trilobites)
• Ordovician Period (485-444 Million Years Ago): Algae and first fish
• Silurian Period (444-419 Million Years Ago): First plants (mosses and ferns)
• Devonian Period (419-360 Million Years Ago): First amphibians
• Carboniferous Period (360-330 Million Years Ago): Giant ferns, coal formation
• Permian Period (330-252 Million Years Ago): First reptiles

Geology: Rodinia breaks into several tectonic plates, which collide again to form Pangaea. Caledonian and Hercynian orogenies.

Climate: Transition from cold climate to very hot climate.

Mesozoic Era (252-66 Million Years Ago)

• Triassic Period (252-220 Million Years Ago)
• Jurassic Period (200-145 Million Years Ago)
• Cretaceous Period (145-66 Million Years Ago)

Geology: Pangaea breaks into different continents.

Climate: Warm with no glaciation; sea level rising, leading to the formation of oil.

Biosphere:

• Reptiles diversify
• Dinosaurs (Jurassic)
• First mammals (Triassic)
• First birds (Jurassic)
• Major extinction caused by a meteorite impact, leading to dust and particles in the atmosphere, lower temperatures, and climate change.
• First gymnosperms (Triassic-Jurassic)
• First angiosperms (Cretaceous) - flowers and fruits

Cenozoic Era (66 Million Years Ago - Present)

• Tertiary Period (66-2.6 Million Years Ago)
• Quaternary Period (2.6 Million Years Ago - Present)

Geology: Pangaea continues to separate, but some pieces also start colliding, leading to the Alpine orogeny.

Climate: Cooling down, but not continuously; glaciations followed by interglacial periods.

Biosphere:

• Mammals and birds diversify and dominate
• First hominids (Quaternary)
• Flowering plants diversify