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Geologic Timescale. How long ago were the dinosaurs here? How do we even describe geologic time anyway?. How is Geologic time divided? ( E xcellent question, grasshopper.). EONS which are divided into ERAS , which are divided into PERIODS , which are divided into EPOCHS
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Geologic Timescale How long ago were the dinosaurs here? How do we even describe geologic time anyway?
How is Geologic time divided?(Excellent question, grasshopper.) EONS which are divided into ERAS, which are divided intoPERIODS, which are divided intoEPOCHS Divided into sections according to the fossils we find of that age
Periods worth noting: 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
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!
Geologic Timescale What if we reduced the WHOLE history of the Earth to the length of a football field? Yup, we’re doing it.
On this scale, the Cambrian (first fishes) would be 88 yards downfield. ? 88 yds ago = 88 yards downfield before first complex organisms! 100 yds ago 4,500 mya 543 mya
This means that from the Cambrian to NOW all fits within 12 yards! 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.
On this scale, the dinosaurs died out: ? 1.4 yds ago = 100 yds ago 4,500 mya 65 mya
On this scale, the you were born: ? 0.0000003 yds ago = 100 yds ago 4,500 mya That’s 3 hundredths of a micrometer. Yep, your life is tiny compared to the Earth. 0.0000015 mya
YOUR ASSIGNMENT: • 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.