Lithotsunami!

In the Lansjärv area in northern Sweden lies an escarpment of rock about 15 m high that stretches for 150 km.  It looks like a stone wave that never broke, frozen in time.  It’s actually an extremely pronounced fault, unusual for an area that experiences as few earthquakes as the United States’ Midwest in that it would have taken an earthquake measuring over 8.0 on the Richter scale to be created.  In fact, some seismologists speculate that the fault, running 40km deep in a relatively stable area, is actually from an externally induced earthquakes – meaning shifts in the earth of unimaginable force.  Wayyy off the Richter scale.  So powerful, they could have generated Rock Tsunamis – or lithotsunami, more accurately.  Appropriate, since Parvie means “wave in the earth” in old Lappic.

Where then did it, and similar faults in that area, come from?

The Parvie Fault - the only picture I could find of it online, from http://www.geo.ucalgary.ca/~wu/TUDelft/LatHetEQ.pdf

Geologists date the creation of this fault to about 9,000 years ago.  They surmise that it was created just after the last ice-age during events called post-glacial rebound.  During the last ice-age, when massive glaciers that covered a good portion of the northern hemisphere, the earth beneath them was compressed a good deal, in a state called isostatic equilibrium.  When much of that ice melted and the waters ran to the sea, the weight was redistributed more evenly and the land began to rise.  The earth isn’t a hard piece of solid rock – it’s got a thin crust with thick, viscous magma beneath it that gives and stretches like a jelly doughnut.

Well, at least from space it can seem so fluid and even.  The crust itself is still hard rock, and for the tiny creatures (including us) living on it, this crustal rebound was generally a violent affair.  Trillions of tons of earth creaking back into place generated powerful earthquakes where previously none had been before, or would be ever again. Ice core data reveals that volcanic activity and post-glacial sea level rise near Iceland were concurrent!

All this geo-drama is enough to probably have spawned the Norse myth of Ragnarok, where the entire pantheon goes to war, spawning reams of volcanic activity, earthquakes, and ultimately the drowning of the world.

“On the day of doom, mighty quakes split the earth and cause the mountains to crumble.  Loki, securely bound since the death of Balder, breaks free from his fetters, and so does his son Fenrir, the monstrous wolf with gaping jaws, and Garm, the evil hound of hell. The world serpent named Jormungard, another of Loki’s sons, rises from his home in the sea, spitting poison into the sky and causing huge waves to wash upon the land.  ‘The ghostly ship Naglfar, made from the nail clippings taken from the dead, rides upon the waves with Loki at its helm.”

From Thematic Guide to World Mythology, Lorena Laura Stookey

Okay, maybe not the part about the nail clippings…but anyone living in the Scandinavia at the time would have had stories to tell for generations to come.  This is not idle speculation, for Scandinavia was quite populated 9,000 years ago.

Now, the final question is, with the melting of our glaciers from the most recent global warming, do we have to worry about similar crustal rebound?  Probably not so much, for we’re talking about a fraction of the mass of the glaciers from the last ice-age.  There are many other factors that seismologists usually weigh when considering this issue such as mantle viscosity.  However, if the ice from an entire continent melts – Antarctica of course- we’ll have one more concern on top of all the other consequences that come with the rise of sea levels.

To find out more, there are lots of scientific articles for those who have access or dare to pay the absurdly steep price-

http://jgs.geoscienceworld.org/cgi/content/abstract/149/2/285

http://www.scienceonline.org/cgi/content/summary/274/5288/735 – Arch C. Johnson, “A Wave in the Earth”.  If you can get access to this article, it’s one of the most informative.

http://adsabs.harvard.edu/abs/2006AGUFM.G33B0068P

http://www.springerlink.com/content/ng8276u453114154/ – on post-glacial volcanic activity

Some sources are a bit more open…though wikipedia stays silent on Parvie itself.

http://www.geo.ucalgary.ca/~wu/TUDelft/LatHetEQ.pdf (This one has 2 photos of the fault)

http://en.wikipedia.org/wiki/Post-glacial_rebound

And, by far the most thorough and reasonably accessible collection of information is in Underworld by Graham Hancock, pages 71-74.