Geologic Time Scale

Earth’s History Continued… Now that we have all of these pieces of evidence, we are able to reconstruct a timeline of Earth’s History…we call this timeline the Geologic Time Scale.

What do we call these major events or changes? Geologic Time Scale Geologic Time Scale – a timeline of Earth’s History divided by major events or changes on Earth What do we call these major events or changes?

Catastrophic Events Catastrophic Events – events that cause major destruction or change life completely Examples: Mass extinctions Ice Ages Meteor strikes Major volcanic eruptions

EONS – largest division of time 4 Eons of Time: 1. Hadean 2. Archean 3. Proterozoic 4. Phanerozoic The first 3 eons make up Precambrian Time which is 90% of Earth’s History! It lasted nearly 4 billion years of Earth’s 4.6 billion year history!

PRECAMBRIAN TIME MAIN EVENTS: After Earth & its moon were formed, there was… Major volcanic activity leading to the formation of Earth’s Crust! Oxygen levels in the atmosphere rise! Single-celled micro-organisms; simple multi- celled organisms, like sponges & jellyfish, in the ocean towards the end. NO animals or plants on land!

Phanerozoic Eon – 544 million years ago – present day Explosion of Life! Contains 3 Eras: Paleozoic Era – “Age of Amphibians” Mesozoic Era – “Age of Dinosaurs” Cenozoic Era – “Age of Mammals”

Paleozoic Era = “Ancient” 544 mya – 248 mya More diverse marine life such as fish and amphibians developed Life begins moving onto land towards the end of this era Reptiles, insects, and simple land plants like ferns developed Pangaea exists about 280 million years ago Ends with a Mass Extinction possibly from a meteor strike (???) – kills 90% of all ocean species and 70% of land dwellers!

Mesozoic Era = “Middle” 248 mya – 65 mya Pangaea begins to break apart about 200 million years ago! Dinosaurs rule the land! Small early mammals, birds, and more complex flowering plants and flying insects are seen Ends with another Mass Extinction due to meteor strike off the coast of Mexico Dust cloud blocked sunlight, killed plant life and affected the food chain

Cenozoic Era =“Recent” 65 mya – Present First primates appear Primitive whales enter the ocean Larger land mammals like horses, pigs (have hooves) cats, dogs, bears Animals developed migration techniques and coevolution patterns Quaternary Period = the past 2 million yrs Last Ice Age ends 1st modern humans leading to Homo Sapiens and modern civilizations

Geologic Time Scale Summary The Geologic Time Scale is divided by catastrophic events; not equal time segments! In general, life goes from simple to more complex! Most life occurs towards the end of the Geologic Time Scale!

The Clock of Eras The last comparison put Earth’s Geologic Time Scale into 1 year – but what if we put it into 1 day? http://www.youtube.c om/watch?v=H2_6cq a2cP4