Geologic Time Scale Lesson 4 Essential Question Learning Objective: Explain how geologists use the geologic time scale to divide Earth’s history. Standard: Evidence of the dynamic changes of Earth’s surface through time is found in geologic record. Divide Your Parents Lives? — Divide your parents life into sections!!!

— You must include at least 5 different sections. — Write them down and then share with your neighbor and discuss how they divided their parents life. 2 Types of Change — Catastrophism: principle that states that all geologic change occurs suddenly — Early Scientists beliefs – all things formed during a rapid change — Ex. – Volcanic Eruptions — Uniformitarianism – the present is the key to the past — James Hutton studied rock formation in Scotland — His findings led to the foundation of modern geology

Uniformitarianism — The process that we observe today, such as erosion and deposition, does not change over time.

— This idea states that the same geologic processes that shape Earth today have been at work throughout Earth’s history.

— The average rate of geologic change is slow and has remained relatively slow over time Geologic Time Scale — Earth is 4.6 Billion Years Old

— Scientists use the geologic time scale to make sense of the amount of time.

— Geologic Time Scale – divides the Earth’s history into intervals of time defined by major events or changes

But Why would we want to do that? Geologic Time Scale Geologic History — Eons (Largest Unit) — Hadean, Archean, Proterozoic, Phanerozoic — Precambrian – Hadean, Archean, Proterozoic — (90% of Earth’s History) — Eras — Phanerozoic (3 Era’s: Paleozoic, Mesozoic, Cenozoic) — Periods — Epochs - (Smallest Unit) Fossil Record

— 5 divisions of geologic time have ended in large mass extinction events — Ex. – 250 Million Years ago largest extinction ever known (90% Marine and 70% Land)

— Causes of Extinctions vary. — Movement of continents? — Lowering of global sea level — Rapid climate change — Asteroid impacts Precambrian Time Outlined — Began with the formation of Earth — 4.5 to 3.6 BYA Earth formed Oblate Spheroid — Tectonic Activity Began

— Atmosphere was forming — Water vapor was added to atmosphere — Cyanobacteria began releasing Oxygen — Earth’s Land Surfaces were located near the poles and covered in ice.

Paleozoic Era — Began 540 million Years Ago — Formation of Pangaea began — Sea Level Dropped — Pangaea drifted away from the South Pole — All life was in the Oceans — Era ended 250 MYA with Mass Extinction

Mesozoic Era — Began 250 MYA — Breakup of Pangaea — Mid Ocean Ridge Began to appear — Carbon Dioxide was added — Domination of Dinosaurs — 65 MYA Mass Extinction — Thought to be caused by asteroid impact

Cenozoic Era — Began 65 MYA — Greenland Split apart from North America and Europe — Final breakup of Pangaea — Continents assumed their present positions — Himalaya’s were formed

— Temperature differences became extreme at poles — Evolution of Modern Humans

Exit Slip — One sentence Answer

— What is the importance of the geologic time scale?