A no-brainer for every earth scientist: time travel!

Because this is a WordPress blog, I receive the weekly WordPress writing challenges, which are all about encouraging and helping aspiring fiction writers, which I am not.

However, this week’s challenge is irresistible – Time Travel! This is the challenge (I took out references to other human beings): we’re giving you a free ticket to the period and place of your choice.. be an invisible observer or an active participant…  let bygones be bygones and just travel in time to the future – don’t forget to come back to tell us how it was (http://dailypost.wordpress.com/2014/03/31/writing-challenge-time-machine/)

Every earth scientist badly desires to go back in time, sometimes to a time period that has been the subject of a research project, sometimes to a time period that just seems fascinating. If I could pick just one period and place, what would be my choice?

My choice is going to depend on the answers to a few other questions that the WordPress challengers didn’t formulate (they didn’t think of earth scientists, alas).

1. How long do I get to stay? Geologic processes take a long time and if I only get a human life span for this trip, then quite a few choices fall by the wayside. A lot of geologic events qualify as extremely boring from a human perspective because they last too long! For example, I would not choose to observe the complete eruption of the Deccan Traps, a 50,000 km2 basalt blob that forms the core of the Indian subcontinent, because that ‘event’ lasted from 68-60 million years ago. You can’t watch only 10-5 of that event (one human life span) to get what you want out of that observation. And while you may think that this was an excruciatingly slow eruption, it was quite sudden and short-lived from the perspective of earth itself. Some scientists think that it exponentially increased the amount of CO2 and GHG in the atmosphere so much that this became a crucial factor in ‘killing the dinosaurs’ (popular speak) at end of the Cretaceous. We have known the end of the Cretaceous as the end of the ‘age of reptiles’ for a long time. Their extinction vacated a niche that subsequently became occupied by a tiny mammal (a sort of vole) and this eventually paved the way for the big mammal take-over including ourselves.                           File:Kille Rajgad from Pabe Ghat.jpg

Field view of the Deccan Traps (Wikimedia)    

 

 Location of the Deccan Traps (www.whoi.edu)

 

2. Do I get to be immune if I choose to visit to a catastrophic geologic event? The great classic being of course the asteroid impact that killed those dinosaurs around 65 million years ago. It would be something to behold, but unless I’d be given supernatural powers (or a very advanced planetary rover maybe?), I wouldn’t survive the observation. I’d love to watch that, though – but from where? I think I’d go sit on the edge of the Cretaceous Edwards Plateau in what is now Austin, TX because I’d like to see the tsunami. I worked in Austin for two years and used to hike the dry river beds north of the city and these amazing deposits on top of the Edwards limestone along the creeks. They looked like regular braided river deposits to me, but at the time the Chixchulub crater had not been located yet (the whole hypothesis of the end-of-Cretaceous asteroid was considered pure speculation by many), so we didn’t think of researching whether they would be something else. But now some of those gravels are considered Chixchulub-impact tsunami deposits (e.g. this article), although that’s still doubted by others. (e.g. here).

Fig 5

Location of Chixculub crater and sites of interpreted tsunami deposits around the Gulf of Mexico. My 1980’s hikes took place just south of the Brazos River site

Having considered all this, I have decided to stay low-risk, I’m going back about 3,500 years and I’m going to my own back yard: Nova Scotia’s Minas Basin, the northeastern extent of the Bay of Fundy.

Minas Basin Glooscap

 

Location of the Bay of Fundy and (insert) hypothetical paleogeography of Minas Basin around 3,500 years ago. W=Wolfville (where I live).

As sea level rose during the rapid warming after the latest ice age, the continental shelf and what is now the Bay of Fundy became quickly inundated. The timing of that inundation has been well documented through countless carefully collected C-14 dates, but there was always an inconsistency between the dates obtained in the Bay of Fundy proper and those in Minas Basin, suggesting that Minas Basin flooded later and that the increase in tide range (Minas Basin has the highest recorded tides in the world) happened quite suddenly. around 3,500 years ago.

A few years ago, a Geological Survey of Canada geoscientist, John Shaw, had a brainwave. What if that was exactly what happened? What if a gravel bar (such as we see everywhere around these previously glaciated coasts) had prevented Minas Basin from marine flooding, ‘holding out’ – if you wish – until some catastrophic event (a storm, likely) breached it after which it the gravel bar never repaired itself again as its remains were constantly attacked by ever-higher tides.

Oddly (or not), the Miqmaq have a legend about their spiritual chief, Glooscap, who wanted to take a bath and asked the beaver to build him a bathtub. Which the beaver did (gravel bar). When he was done with his bath, Glooscap asked beaver to empty the bath, but we know how stubborn beavers are and this beaver was no different, so he refused. Glooscap got mad, threw a couple of rocks at beaver (small islands along the north shore of the basin) and eventually asked the Whale ‘to flip his tail’ and empty the tub. Which the whale did.

Now the former bath tub fills and empties twice every lunar day – and we watch it from our house. John Shaw’s article is referenced below.

I would have loved to sit on top of Cape Blomidon during the event that destroyed this hypothetical gravel bar and watch it happen. The tidal currents are so powerful that no evidence exists of this former gravel bar, so it remains a speculative story, except for those radiocarbon dates.

Would my presence at that time have had any influence on the future evolution of the area? Not my individual presence, not even the presence of a few thousand MiqMaq who lived here at the time. But if this would have happened in the 20th century, society might have intervened, it might have decided that the gravel bar needed protection, locals might have gone about some big engineering construct to ‘keep Minas Basin fresh’ (I can just see the bumper stickers).

And that brings the story back to the human dimension that the WordPress challengers were thinking of.

Reference

Shaw, J., C.L. Amos, D.A. Greenberg, C.T. O’Reilly, D.R. Parrott, E. Patton, 2010, Catastrophic tidal expansion in the Bay of Fundy, Canada. Canadian Journal of Earth Science, v. 47, p. 1079-1091.

 

 

 

 

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About earth science society

I am an earth scientist. Understanding earth is essential for the well-being of our global society. Earth is fascinating, science is fascinating and a better understanding of both can help society forward. This blog attempts to make a contribution to raising awareness of these issues.
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