SCIENCE NEWS • Google wants to buy, sell electricity in US• http://

news.yahoo.com/s/afp/20100108/tc_afp/usitinternetcompanygoogleelectricity

• Experts: Cold snap doesn't disprove global warming

• http://news.yahoo.com/s/ap/20100107/ap_on_sc/sci_big_chill

What do you think?

• How was the Earth created?

• What was the earth like after it was formed?

What are the benefits of studying Fossils and the Rock Record?

Geologist can reconstruct aspects of earth’s history

Geologic Time Scale

Enables scientist to find relationships among geological events,

environmental conditions and fossilized life forms

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Geologic Time Scale• Geologic time scale – Earth history

•Subdivides geologic history into time units•Time units are based largely on the

fossils within the rocks •Originally created using relative dates

Structure of the geologic time units scale

–Eons are subdivided into–Eras are subdivided into –periods are subdivided into –epochs

See text p 591

Eon – the greatest expanse of time

Phanerozoic – “visible life”, most recent eon Proterozoic – before life Archean – ancient Hadean – mythical subterranean world of

departed spirits, oldest eon

Precambrian: Proterozoic, Archean, Hadean

Eons• Largest of the time units • Three earliest eons make up 90% of

geologic time also know as Precambrian • Fossil evidence suggest simple life forms

in the Archean Eon • At end of Proterozoic Eon life evolved

into complex organisms • What eon are we currently in?

What do you think was alive in the Hadean and early

Archean eon?

Bacteria

Era – subdivision of an eon

• 10 – 100 millions of years• Defined by life forms found in the rocksGreek roots• Paleo = old• Meso = middle• Ceno = recent• Zoic = of life

Example: Mesozoic = middle life

Periods• 10 of millions • Named for geographic region in which rocks or

fossils characterizing the age was first observed and described

Epochs• 100 to Millions of years • Rocks & sediments are most complete less

time for weathering and erosion

Evolution & Geologic Time

What Eon, Era, Period and Epoch are we currently living

in? • Phanerozoic,–Cenozoic•Neogene–Plesitocene

When??• What eras were the age of the dinosaurs?

• What era did mammals increase in numbers and diversity?

• What era did the Appalachian Mountains start to form?

ANY QUESTIONS?