Glacial Theory

Hypotheses preceding glacial theory

Early hypotheses were created to explain the diamict and large erratics left behind by glaciers.

Diluvial Theory (Biblical Flood)

• Sediment was deposited by the biblical flood
• Cons:
  • Most glacial sediments are not sorted (diamict)
  • Proof of world-wide flood lacking
  • lack of marine fossils
  • Perching of large boulders at high elevations not explained

Drift Theory (Charles Lyell, 1833)

• Deposits, referred to as "drift", were sediments melted out of icebergs carried in the biblical flood
• Pros:
  • Explained regional flow patterns,
  • perched boulders, and
  • poorly sorted sediment
  • lack of marine fossils in drift
• Cons: Proof of world-wide flood lacking

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History of Modern Glacial Theory

In the early 1800's a number of Swiss observers working in the Alps had already come to the conclusion that glaciers once extended beyond their present boundaries. However, the theory of glaciation never took hold until promulgated by Louis Agassiz. Jean-Pierre Perraudin was a Swiss mountaineer who while hunting in the Alps observed glacial straie and other features down valley of existing glaciers. He eventually interested Swiss engineer Ignance Venetz and naturalist Jean de Charpentier in his findings and started the chain of events that would eventually lead to the widespread acceptance of the theory. Swiss paleontologist Lois Agassiz--known as the father of glacial geology, resisted the concept until the mid 1830's when finally he was convinced by de Charpentier. In 1840 Agassiz presented his theory of continental glaciation in his publication Estudes sur les glaciaires. He later move to US and taught at Harvard--firmly planting the theory in the minds of US geologists. 

Early argument against glaciation:

• Erratics and diamicts were too widespread and flow indicators broadly uniform. They were not restricted to alpine valleys where glaciers were know to exist.
• Causes of glaciation unknown.

Arguments for glacial theory:

• Formation of fresh glacial deposits and erosional features observed in the Alps.
• Exploration of the Arctic in the 1800's proved the existence of ice sheets and promoted the concept of continental glaciation.

Frequency of glacial events

Once the theory of glaciation became firmly established the next step in its development was to determine the causes of glaciation and how many times the continents were subject to glaciation.

• Pre 1960's: Four glaciations were visible in terrestrial record of both North America and Europe.

  North American Terrestrial Record Tills and paleosols	European (Alps) Gravel Terraces and paleosols
  Wisconsin glaciation (80K-11K) Sangamon interglaciation Illinoian glaciation  Yarmouth interglaciation Kansan Glaciation Aftonian interglaciation Nebraskan glaciation	Wurm Riss/Wurm interglacial Riss Mindel/Riss interglacial Mindel Gunz/Mindel interglacial Gunz

• Post 1950: Paleontological and isotopic studies of deep sea cores shows that there were as many as 50 glacial episodes in the last 2.5 my.
  • 1955 Cesare Emiliani uses ¹⁸O content of foraminifera from deep sea cores to identify glacial and interglacial stages. However, ¹⁸O variations were thought to reflect changes in water temperature.
  • 1956. 1968 David Ericson and Goesta Wollin used the changes in the abundance of Globorotalia menardii (a warm water planktonic formam) in deepsea cores to determine Quaternary variations in climate.
  • 1967-69 John Imbri (Columbia Univ) and Nicholas Shackleton (University of Cambridge) independently concluded that changes in ¹⁸O to changes in ice volume.
  • 1967 Wallace Broecker and Robley Matthews (Brown Univ) correlated marine terraces in Barbado and elsewhere with the 82l 105k and 125k interglacials predicted by Milankovitch's 45°N inosolation curve.

Imbrie, J., and Imbrie, K.P., 1979, Ice ages. Solving the Mystery: Erslow Publishers, Short Hills, New Jersey.

Gribbin, J., and Gribbin, Mary, 2001, Ice age. Barnes &Noble, Inc.

• Jean Louis Rodolphe Agassiz and The Birth of Glacial Theory, James S. Aber, Emporia State University
• Temperature from Fossils, The Discovery of Global Warming
• A Core a Day Keeps 'Doc' Happy Building Lamont's Deep-Sea Core Repository , Rusty Lotti Bond, Lamont-Doherty Earth Observatory of Columbia University Twelve Perspectives on the First Fifty Years 1949 - 1999

   

• Just for fun:
  • Learn about the early Polar Explorers: The Heroes If you've got the time and want to learn about Arctic explorers visit this page from the Arctic Philately site
  • Controversy about glacial theory 1996, Douglas E. Cox : Presents information from a creationists viewpoint. A good example of a site not to use for research. Why?

[Glacial and Quaternary Geology] [extended GeoIndex][QkRef][Geological Sciences] [Degree Programs] [Salem State College]
Lindley Hanson (email) Last Modified 2/5/03