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, sealevel 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 devastated by
earthquakes and tsumamis
• Inspired the myth of the lost city of Atlantis
Dramatic, Short-lived Events
Volcanic Eruptions
Summit -9,677’
Crater Base -4,700’
Mt. St. Helens
May 18, 1980
Dramatic, Short-lived Events
Volcanic Eruptions
Mt. Mazama Eruption
6,500 ybp
Great Time Markers!
Dramatic, Short-lived Events
Volcanic Eruptions
Heimaey, Iceland
1983
Dramatic, Short-lived Events
Earthquakes
1326 Aftershocks
1326 Aftershocks
Dramatic, Short-lived Events
Earthquakes
Anchorage, Alaska
1964
9.3 intensity
131 Dead
Dramatic, Short-lived Events
Earthquakes
San Francisco, California - 1906
7.8 intensity
200,000 homeless and >3,000 dead
3 days of fires destroys 70% of city
Dramatic, Short-lived Events
Tsunamis
>200,000 killed
Banda Aceh, Sumatra
9.15
Dramatic, Short-lived Events
In Real Time
Earthquakes
http://earthquake.usgs.gov/earthquakes/map/
Volcanoes
http://www.volcano.si.edu/reports/usgs/
Subtle Geologic Events
Climate Change
The Sahara
10,000 Years ago – Temperate, Humid, Verdant
Subtle Geologic Events
Climate Change
Fertile Crescent
Subtle Geologic Events
Glaciers and Sea Level
Subtle Geologic Events
Glaciers and Sea Level
Cosquer Cave, France
37 m deep entrance
Ibex
Horse - 18,500 years old
Subtle Geologic Events
Glaciers and Sea Level
Greenland's Jakobshavn Glacier
Subtle Geologic Events
Glaciers 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 Northwestern
Europe. Population at risk in the inundation
area is calculated at over 21.7 million people
(Rowley et al. 2007)
Subtle Geologic Events
Glacial Retreat & Crustal Rebound
Subtle Geologic Events
Glacial Retreat and 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
Biblical Creation <6000 yrs
Deluge central to geological interpretation
Late 1700’sMid-1800’s
Catastrophism
Mid-1800’s –
Late 1900’s
Uniformitarianism
Present-day
PuNctuAteD eQuiLibRiuM
The Scientific Method
Next Lecture
Development of
Geological Concepts
QUIZ ON MONDAY!!
Chapters 1 & 2