The Ice Age Revolution
In 1837, the 30-year scientist, Louise Agassiz, caused more than a minor kerfuffle among the stately and turgid members of the distinguished Swiss Society of Natural Science when he refused to discuss his research on the fish of Brazil, and instead, presented his theory on the ice age.
Without knowing it, he kicked off one of the most turbulent disputes in the history of geology.
He was not the first to propose glaciers as an agent of erosion, after all, many geologists before him had recognized glacial moraines and lakes, but he was the first to propose an “age of ice”.
Agassiz proposed that there was a period of time in the not too distant past when the entire northern hemisphere was covered by glacial ice.
He created such a turmoil on that day, that subsequent scientific papers were canceled so scientists could argue about the young Turk’s outrageous remarks.
Agassiz tried to quiet his colleagues by taking them to the nearby mountains and show them his evidence.
They were not impressed.
Indeed, it would take nearly 150 years for the full implications of his glaciation presentation to become common scientific knowledge.
By the early to mid-twentieth century, most geologists subscribed to the notion that vast glaciers once covered the land masses of the northern hemisphere. And it was generally accepted that there were three major periods of glaciation; however, the age and duration of these glaciations was not known.
Multiple Lines of Evidence
Then three separate and unique scientific breakthroughs changed everything.
First, carbon age dating techniques allowed geologists to determine the age of the three known continental glaciations.
Second, oxygen isotope data from deep marine sediment core investigations determined that sea level is not static – sea level goes up and down by more than 425 feet in the North Atlantic during periods of glaciation.
Third, ice cores drilled through the Greenland and Antarctic glaciers provided detailed information on atmospheric conditions from the present to 800,000 years before the present.
By 1980, 150 years after Agassiz’s disruptive presentation in Switzerland, science successfully demonstrated that Earth climate changes drastically in a cyclic manner alternating between long periods of time when continental glaciers cover the most of the land in the northern hemisphere and relatively short periods of time when the land is ice free.
It turns out that Agassiz was correct about the concept of an ice age and continental glaciation, but there wasn’t one ice age, there have been many ice ages, the most recent beginning about 800,000 years before the present.
For the last 800,000 years, Earth has cycled between periods of glaciation and warmth on twenty-one different occasions.
We currently live in an interglacial (warm) period that started about 12,000 years ago. This is approximately 2,000 years before the first evidence of agriculture by humans was observed in the Indus Valley and about 7,000 years before the oldest Pyramids were constructed.
Sometimes it is hard to understand why the scientific community needed 150 years to accept the idea of an ice age.
This is because the scientific method requires proof and re-proof before an idea can become accepted.
Scientific proof needs to be rigorous because, sometimes, scientific ideas challenge our intuition.
During the Last Glaciation
Consider this,12,000 years ago, New York City was located about 100 miles from the ocean and the Hudson River was confined in a great canyon that extended from New York City to edge of the Continental shelf.
The canyon is now flooded under 400 feet ocean water.
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