Category Archives: Interpreting ancient environments

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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Islands with attitude; the devastation wrought by collapse of oceanic volcanoes

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Krakatoa, 1883, and the seas shivered. The eruption, one of the largest in recorded history, delivered tsunamis that swept away entire villages around Indonesia and its neighbours; little more than the flotsam and jetsam of nature’s fickleness.  Five years later, in the same general neighbourhood, nature was at it again.

Ritter Island, barely a speck on most maps, is a volcanic edifice rooted to the floor of Bismarck Sea between Papua New Guinea and New Britain. In 1888, most of the island slid beneath the waves, creating avalanches of rocky debris.  Eye-witness accounts tell of multiple tsunamis over a 3-hour period, and waves at least 8m high with run-ups to 15m above sea level.  Ritter Island is an active volcano, but at that time it was not erupting in any major way.  The island landslide is probably the largest in recent history – more than 4 cubic kilometres of volcanic rock were dislodged and redeposited along the seafloor. Slope failures like this are called volcanic sector collapses. Continue reading

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Lahars; train-wreck geology

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Christmas morning in New Zealand is synonymous with mid-summer barbecues at the beach, deservedly lazy times, perhaps a bit of over-indulgence. That morning, in 1953, Kiwis were expecting to awaken to news of the Royal tour; the newly crowned Queen was doing the rounds of towns and countryside, perfecting that royal wave to flag-waving folk lining the streets. Instead, they awoke to the news of a train disaster near Mt. Ruapehu, one of three active volcanoes in central North Island; a railway bridge on Whangaehu River, near Tangiwai, had been washed out on Christmas Eve.  Train carriages were strewn along the river banks, 151 people were killed.  The culprit was a geological phenomenon known as a lahar. Continue reading

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The origin of life: Panspermia, meteorites, and a bit of luck

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In the opening scenes of Stanley Kubrick’s 2001 Space Odyssey (1968), Neanderthal-like folk are scrounging for food, squabbling with a neighbouring tribe who are intent on competing for the meagre lickings (a reactionary condition that would not bode well for future humanity). One of them picks up a large bone.   There’s instant recognition, seemingly influenced by a black obelisk that appears mysteriously, that it can be used for something else. His neighbour lies in a crumpled heap. In what has become an enduring Sci-fi image, he triumphantly hurls his weapon into the air, whereupon Kubrick transforms it into an orbiting space station. Continue reading

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In praise of field work

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The class field trip is underway.  Teacher hands out the rap-around, virtual imaging glasses, and you are transported to a green horizon. In the background, there is an annoying kind of buzz, as teacher relates the topic of enquiry, asks questions, provides comments. Fellow students may even be projected into your virtual reality, their essence reduced to pixels. There’s a resounding crash – one student, suffering from vertigo, has fallen off their chair. Another has just thrown up from motion sickness.  All in a day’s field study. Off come the glasses. The green horizon vanishes. All except one of your classmates are still in their chairs, surrounded by the same four classroom walls. What was learned? Continue reading

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Life on Mars; what are we searching for?

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I believe alien life is quite common in the universe, although intelligent life is less so. Some say it has yet to appear on planet Earth. Stephen Hawking

I can only imagine H.G. Wells bitter disappointment if he were to learn that Martians were little more than primitive microbes.  All that hype and scare-mongering for nothing. Because that, it seems, is all we are ever likely to find on Mars. They may be intelligent microbes, but microbes nonetheless.

Present conditions on Mars are not conducive to thriving populations of anything living – at least in any life form we are familiar with. Incident UV and other solar radiation, low atmospheric pressure, an atmosphere almost devoid of oxygen, and the presence in soils of oxidizing molecular compounds such as perchlorates and hydrogen peroxide (think bleached hair), all contribute to rather inclement living conditions. It is possible that some life forms have survived these ravages, in sheltered enclaves or buried beneath the scorched earth, but it is more likely that, if life did exist on Mars, we will find the evidence written into ancient sedimentary rocks, or perhaps as chemical signatures.  It is these attributes that current exploration programs, both landed rover expeditions and orbiting satellites, tend to focus on. Continue reading

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