Ice age Imagination of ice Ice cycles Commentary

Louis Agassiz atmospheric sciences

Ice age

• Rock beds and faces of rock show parallel grooves
• as though gravel locked in moving blocks of ice had scraped them.
• Unstratified beds of rounded gravel lay under topsoil
• as though they were produced by the trituration
• of sheets of ice moving over the surface.
• Rock debris arcs across the ends of valleys
• as if they were pushed only so far by glaciers.
• Slopes and summits are dotted with erratic rocks
• as if they were randomly dropped by retreating ice.
• Many people had suggested that the northern hemisphere
• had been covered with sheets of ice
• but it had not been scientifically established
• until Louis Agassiz put aside his work as an ichthyologist
• identifying species of fossil fishes
• and discussed these things
• with Jean de Charpentier and Karl Friedrich Schimper
• who had gotten their ideas from local inhabitants—
• a woodcutter and a chamois hunter.
• Agassiz made several trips to the alps
• with Charpentier and Schimper
• built a hut on one of the Aar glaciers
• made detailed observations of the ice
• supporting the theory—
• that before the elevation of the Alps
• vast sheets of ice extended
• from the North Pole southwards
• over northern Asia
• over North America
• and over Europe to the southern slopes of the Jura Mountains.
• Agassiz published Etudes sur les glaciers in two volumes
• giving no credit to Charpentier or Schimper
• and personally convinced the influential geologist William Buckland
• that ice once covered Scotland.
• Buckland then convinced other scientists.
• Thus the idea of the ice age was established.

Imagination of ice

• The image of grand and gruesome sheets of ice
• covering our steep mountains and green valleys
• not once but five times
• captures the imagination.
• Strange mammals gone extinct—
• the mastadon and mammoth,
• the glyptodon, a Pleistocene armadillo,
• the smilodon, a saber-toothed cat,
• the megatherium, a sloth as big as an elephant—
• give us a larger and more dangerous world
• than the world we think we live in.

Ice cycles

• Cycles of thawing and freezing
• hang icicles from eaves.
• Popsicles, Eskimo pies, and ice cream
• are as crude as frozen meat
• compared to ice in a bird bath
• forming a crystal sheet.