Week 9: Geologic Time

Lab: 

Earth viewer Activity: 

Earth and Moon formed ~4500 Mya

The oldest minerals show evidence of liquid water on Earth (~4400 Mya)

About 2.4 billion years ago, oxygen began to persist in the atmosphere. Before then, life did not necessitate oxygen. 

Snowball earth -- earth was covered in ice (2200-2000 Mya) 

Cambrian explosion (540 Mya) -- diversification of life

First land plants: (470 Mya) 

First land vertebrates (375 Mya) 

Permian-Triassic Extinction (~251 Mya) referred to as "The Great Dying" or the largest extinction event in history

Genus Homo (2 Mya) 

Homosapiens appeared much later -- 0.2 Mya

With young students, it is helpful to use a timeline to illustrate the concepts of earth's conception and beyond. With the students, it could be easiest to create a timeline that details the last billion years to be more specific with a smaller span of time.

Pressbook: 

- The first life on Earth was simple, prokaryotic bacteria.

- At least three times in Earth's history, the planet was almost entirely covered in ice -- a phenomenon called snowball earth. They found evidence of this through sedimentary rocks. A positive feedback loop kept the ice from melting until volcanoes erupted during the snowball earth ended up melting the ice, creating water. The water absorbed more energy than the ice, warming the planet and ending snowball earth. 

- We know that Pangea broke up and created the continents that we have now, but some scientists hypothesize that a new supercontinent could form in around 250 million years.

- Wegener had great ideas about continental drift and the formation of a supercontinent but was unable to explain why the continents broke apart or shifted. That theory would come later with plate tectonics.