Monthly Archives: December 2017

Ropes, pillows and tubes; modern analogues for ancient volcanic structures

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Analogies are the stuff of science. In geology, we frequently employ modern analogies of physical, chemical, or biological processes to help us interpret events that took place in the distant past. We cannot observe directly geological events beyond our own collective memory. Instead, we must infer what might have taken place based on evidence that is recorded in rocks, fossils, chemical compounds, and the various signals that the earth transmits (such as acoustic or electrical signals).  Analogies are not exact replicas of things or events, although they may come quite close. Their primary function is to guide us in our attempts to interpret the past.  As such, they are part of our rational discourse with deep time. Analogies are at the heart of the concept of Uniformity espoused by our 18th and 19th century geological heroes, James Hutton and Charles Lyell; they are the foundation for the common dictum “the present is the key to the past”, coined by Archibald Geikie, an early 20th century Scottish geologist.

Even though lots of people have written about this, I figure one more example that illustrates the methodology won’t hurt. Forty years ago, I worked on some very old rocks on Belcher Islands, Hudson Bay, that included volcanic deposits. Looking at the photos (35mm slides), I still marvel at the geology, the fact that something almost 2 billion years old is so well preserved, makes it look like the volcano just erupted.

Here are three ancient structures that were constructed by flowing basalt lava. Each can be compared with modern volcanic structures and processes that we can observe directly.  We can interpret the ancient structures according to the similarities and differences between the modern analogues and the ancient versions. The examples are from strata known as the Flaherty Formation, a succession of volcanic rocks exposed on Belcher Islands, Hudson Bay. Continue reading

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Polar bears do not live in the Antarctic, there are no Penguins in the Arctic. The asymmetry of the poles

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This post is about asymmetry – the Arctic and Antarctic polar regions. They are the most frigid places on Earth, but that is about all they have in common; with one other exception –  they are both stunningly beautiful. I can attest to this for the Arctic, or at least the Canadian Arctic Islands where I spent several summers; but I’ve never been to Antarctica. Visual treats everywhere. And silence – above the wind and the hum of a few insects – silence.

There is an intriguing asymmetry in their respective geographies, the timing of ice accumulation, present climates, the flora and fauna. What follows are a few comparisons and contrasts. Continue reading

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