THE GEOLOGICTIME SCALE

MASS EXTINCTIONS• 99.9% of all living things that have ever existed on earth have gone extinct• earth has experienced 5 five extinctions

GEOLOGIC TIME SCALEEra• Largest unit of geologic time • lasts tens to hundreds of millions of years and

consists of two or more periods. Period• Divides Eras• Most commonly used units of time scale• Lasts millions of years• Each is associated with a particular rock systemEpochs• Divide Periods• Smallest unit of geologic time• Lasts several million years

PRE CAMBRIAN

Life Climate/AtmosphereBacteria,sponges

• CH4, NH3, H2, C• Volcanic eruptions,

lightening• Some areas freeze

PALEOZOIC ERA

CAMBRIAN544-505 MYA

Life Climate/Atmosphere• “Cambrian Explosion” =

jellyfish, starfish, worms, sea scorpions

• Trilobites dominant

• Warm/tropical• No glaciation

ORDOVICIAN505-440 MYA

Life Climate/Atmosphere• Mass extinctions of

marine life• Invertebrates dominant

• Starfish, clams, oysters, squids, octopuses

• Land masses gather at south pole

• Massive glacier form dropping sea levels

SILURIAN440-410 MYA

Life Climate/Atmosphere

• Earliest land plants• First Jawfishes • Trilobites, sea scorpions,

mollusks still common

• Pangea forms• Tropical climate• Glaciers melt• Ocean rises• Warm shallow seas

form

DEVONIAN410-360 MYA

Life Climate/Atmosphere

• First sharks, amphibians, insects, and trees

• Extinction of armored fish

• Very warm

CARBONIFEROUS360-286 MYA

Life Climate/Atmosphere• Amphibians, winged

insects, small reptiles, and conifers and ferns

• Warm tropical areas• Glaciers at poles

PERMIAN286 – 245 MYA

Life Climate/Atmosphere• Centipedes, spiders, and

cockroaches • Seed plants• Reptiles abundant• Beetles first appear• Many inverts go extinct

• Temperatures increase• Sea levels rise

MESOZOIC ERA

TRIASSIC245-208 MYA

Life Climate/Atmosphere• Turtles, crocodiles, and

lizards appear• Sharks, sea urchins,

seastars are abundant• Early dinosaurs (ex.

placodont)

• Sea levels rise• land is very dry and

hot. • glaciers melting.

JURASSIC208-146 MYA

Life Climate/Atmosphere• Insects, sharks, crocodiles,

and fish are abundant• The earliest mammals

appear. • Early dinosaurs are abundant

• Hot• No glaciers

CRETACEOUS146-65 MYA

Life Climate/Atmosphere• “Age of the

Dinosaurs”• Flowering plants

and bees

• Pangea splits apart creating more coastline• Seasons begin to form

CENOZOIC ERA

TERTIARY65-1.8 MYA

Life Climate/Atmosphere•“Age of Mammals”•Grasslands, forests, palm trees, kelp forests•Birds evolve

•Started tropical and then started to cool•Continents crashed into each other creating mountains

QUARTERNARY1.8 MYA- PRESENT

Life Climate/Atmosphere•First appearance of woolly mammoth, giant sloth, saber-toothed cats

•Went through an ice age•Temps warmed and continue to