Earth History GEOL 2110 Lecture 2 Scales of Time and Change

Major Concepts Geological events cover huge amounts of time that are hard to grasp in the span of human life We tend to focus on dramatic, short-lived geologic events that we witness and are unaware of subtle, but geologically important events Very often, short dramatic events are just parts of long-lived processes (e.g. mountain building, sea- level change) Rates of geologic change can be linear, non-linear, periodic or episodic

Dramatic, Short-lived Events Volcanic Eruptions Krakatoa, 1883 left a 3000m deep crater ash dispersed 2000km away heard 5000km away 40m high tsunamis lowered global T for 2yrs

Dramatic, Short-lived Events Volcanic Eruptions Santorini/Thera – 3,600ybp 3-4x bigger than Krakatoa Minoan civilization on Crete to devastated by earthquakes and tsumamis Inspired the myth of the lost city of Atlantis

Dramatic, Short-lived Events Volcanic Eruptions Mt. St. Helens May 18, 1980 Summit -9,677’ Crater Base -4,700’

Dramatic, Short-lived Events Volcanic Eruptions Mt. Mazama Eruption 6,500 ybp Great Time Markers!

Dramatic, Short-lived Events Volcanic Eruptions Heimaey, Iceland 1983

1326 Aftershocks Dramatic, Short-lived Events Earthquakes 1326 Aftershocks

Dramatic, Short-lived Events Earthquakes Anchorage, Alaska , 131 Dead

Dramatic, Short-lived Events Earthquakes San Francisco, California ,000 homeless and >3,000 dead 3 days of fires destroys 70% of city

Dramatic, Short-lived Events Tsunamis Banda Aceh, Sumatra 9.15 >200,000 killed

Dramatic, Short-lived Events In Real Time Earthquakes Volcanoes

Subtle Geologic Events Climate Change The Sahara 10,000 Years ago – Temperate, Humid, Verdant

Subtle Geologic Events Climate Change

Subtle Geologic Events Glaciers and Sea Level

Cosquer Cave, France 37 m deep entrance Horse - 18,500 years old Ibex

Subtle Geologic Events Glaciers and Sea Level Greenland's Jakobshavn Glacier

Subtle Geologic Events Glaciers and Sea Level Projected sea level rise (5 m) for Northwestern Europe. Population at risk in the inundation area is calculated at over 21.7 million people (Rowley et al. 2007) Current climate models predict that sea levels will rise cm over the next century Melting 10% of Greenland and Antarctic Ice Sheets would produce ~5 m rise in sea level

Subtle Geologic Events Glacial Retreat & Crustal Rebound

Subtle Geologic Events Glacial Retreat and Crustal Rebound

Rates of Geological Processes Linear Change (rare in nature) Non-Linear Change (more common)

Rates of Geological Processes Periodic to Episodic Change Most Common to Geological Processes

Evolution of Ideas about Rates of Geological Processes Pre-1700 Late 1700’s- Mid-1800’s Mid-1800’s – Late 1900’s Present-day Biblical Creation <6000y Deluge central to geological interpretation Catastrophism Uniformitarianism PuNctuAteD eQuiLibRiuM

Next Lecture Development of Geological Concepts QUIZ ON MONDAY!!