Geologic Timescale How long ago were the dinosaurs here? How do we even describe geologic time anyway?

 EONS which are divided into ERAS, which are divided into PERIODS, which are divided into EPOCHS  Divided into sections according to the fossils we find of that age How is Geologic time divided? (Excellent question, grasshopper.)

 Cambrian (543 mya): first fish fossils, lots of marine species  Silurian (443 mya): first land plants and animals  Triassic (248 mya): begin the age of the reptiles!  Tertiary (65 mya): mammals diversify  Quaternary (2 mya): hominids develop Periods worth noting:

The end of an ERA:  Some periods end when there is a stark shift in the kinds of fossils in the rock record—which sometimes means a…  A MASS EXTINCTION EVENT!

 What if we reduced the WHOLE history of the Earth to the length of a football field? Yup, we’re doing it. Geologic Timescale

543 mya On this scale, the Cambrian (first fishes) would be 88 yards downfield. 4,500 mya = ? 100 yds ago 88 yds ago 88 yards downfield before first complex organisms!

 Animals transitioned to land  Dinosaurs  Pangaea  the evolution of flowering plants  the Roman Empire  The Revolutionary War  your parents’ high school experiences  I was born …  you were born. This means that from the Cambrian to NOW all fits within 12 yards!

On this scale, the dinosaurs died out: 65 mya 4,500 mya = ? 100 yds ago 1.4 yds ago

On this scale, the you were born: mya 4,500 mya = ? 100 yds ago yds ago That’s 3 hundredths of a micrometer. Yep, your life is tiny compared to the Earth.

 Get comfortable with the geologic timescale.  Get together with 3 or 4 other people (so, that’d be a group of 4 or 5, right?)  Pick a length (time, distance, duration) to represent all of the Earth’s history.  Do the math.  All periods Cambrian-Tertiary  Pleistocene AND Holocene epochs  Be ready to share TWO or THREE highlights (discoveries-o- coolness) with the rest of us. YOUR ASSIGNMENT: