Earth History GEOL 2110

1. Earth History GEOL 2110 Lecture 2 Scales of Time and Change

2. 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

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

4. Dramatic, Short-lived EventsVolcanic 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

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

6. Dramatic, Short-lived EventsVolcanic Eruptions Mt. MazamaEruption 6,500 ybp Great Time Markers!

7. Dramatic, Short-lived EventsVolcanic Eruptions Heimaey, Iceland 1983

8. Dramatic, Short-lived EventsEarthquakes 1326 Aftershocks 1326 Aftershocks

9. Dramatic, Short-lived EventsEarthquakes Anchorage, Alaska 1964 9.3, 131 Dead

10. Dramatic, Short-lived EventsEarthquakes San Francisco, California - 1906 7.8 200,000 homeless and >3,000 dead 3 days of fires destroys 70% of city

11. Dramatic, Short-lived EventsTsunamis >200,000 killed Banda Aceh, Sumatra 9.15

12. Dramatic, Short-lived EventsIn Real Time Earthquakes http://earthquake.usgs.gov/earthquakes/map/ Volcanoes http://www.volcano.si.edu/reports/usgs/

13. Subtle Geologic EventsClimate Change The Sahara 10,000 Years ago – Temperate, Humid, Verdant

14. Subtle Geologic EventsClimate Change

15. Subtle Geologic EventsGlaciers and Sea Level

16. Subtle Geologic EventsGlaciers and Sea Level CosquerCave, France 37 m deep entrance Ibex Horse - 18,500 years old

17. Subtle Geologic EventsGlaciers and Sea Level Greenland'sJakobshavnGlacier

18. Subtle Geologic EventsGlaciers and Sea Level Melting 10% of Greenland and Antarctic Ice Sheets would produce ~5 m rise in sea level Current climate models predict that sea levels will rise 25-60 cm over the next century Projected sea level rise (5 m) for NorthwesternEurope. Population at risk in the inundation area is calculated at over 21.7 million people(Rowley et al. 2007)

19. Subtle Geologic EventsGlacial Retreat & Crustal Rebound

20. Subtle Geologic EventsGlacial Retreat and Crustal Rebound

21. Subtle Geologic EventsGlacial Retreat and Crustal Rebound

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

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

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

25. Next Lecture Development of Geological Concepts QUIZ ON MONDAY!!