Of Mosses and Mountains II and AW #60

The Apennines -- home to momentous discoveries in geology.

As mentioned earlier, my summer reading included two outstanding books about natural history.  The first, Gathering Moss by Robin Kimmerer (reviewed here), is about the miniature fairy-tale world of mosses.  The second concerns the other extreme -- a world at an almost-incomprehensible scale where landscapes are as ephemeral as patches of moss.  This is The Mountains of Saint Francis, by Walter Alvarez (W.W. Norton, 2008; also recommended by Rapid Uplift and About.com Geology).

As hinted at in the subtitle -- Discovering the geologic events that shaped our earth -- Alvarez uses the Apennines of Italy as a venue for describing great discoveries in geology.  He tells of the brilliance of the discoverers, the far-reaching effects of their discoveries, and the generally reluctant acceptance by colleagues.

How nice that the topic for this month’s Accretionary Wedge happens to be Momentous Discoveries in Geology!  Thanks to Matt at Geosphere for his timely choice :-)

“The discovery you choose does not have to be universally recognized as momentous but should be in your opinion. It could be something that we take for granted every day, but is in actuality part of the underpinnings of our science.”

After reading The Mountains of Saint Francis, my choice is the very basic realization that the Earth changes at a scale well beyond that of our lifetimes.  We might see a volcano pour out massive amounts of ash, or suffer through a destructive earthquake, but these are just minor events.  Consider that mountain ranges are uplifted and then worn away, and that continents move around, collide, split and even sink, coming apart in the process. Humans can only experience these kinds of changes with their imaginations, and even that wasn't always possible.

Who was it that “discovered” that the Earth has a history well beyond what is witnessed by humans?  Alvarez credits Nicolas Steno (1638-1686), often considered the founder of geology.  So the Earth changes ... I certainly take this for granted, it seems so obvious! But in Steno’s day it wasn’t easy to convince people that seemingly abiding landscapes are ephemeral.

Source.

Fossils were the key to Steno’s “discovery”, allowing him to argue convincingly that the hills around Tuscany once were sediments on the ocean floor, even though no human had seen nor recorded such a spectacular change.  At the time, fossils were considered growths within rocks in spite of obvious similarities to living organisms.  Steno was not the first to propose that fossils were once alive, but his careful studies and convincing arguments led to general acceptance.  He saw the problem as one of explaining “a solid body naturally contained within a solid” (De solido intra solidum naturaliter contento), and noted that:

If a fossil had grown within a rock it would distort or crack the rock, which was never the case.

Many fossils appeared to be falling apart rather than growing; in fact discrete fossils sometimes fit together perfectly.

Fossils were never distorted in shape, contrary to what would happen if growing in hard rock (like tree roots).

Fossil shells were sometimes found in clusters, arranged just as they are in the ocean.

Steno reasoned that rocks containing fossils and other solids had once been fluid, and had hardened around those solid objects.  Thus seashells fossilized in the mountains had once lived in the ocean, i.e. the mountains had not always been there.  The Earth has undergone huge changes; it has a history, which geologists have been working to unravel ever since.

"One sins against the majesty of God by being unwilling to look into nature's own works and contenting oneself with reading others" said Bishop Steno.

Steno’s mind in action must have been awesome to behold.  From his study of fossils, he went on to explain layered rocks (principle of original horizontality) and how they can provide powerful insight into the history of the Earth (law of superposition).  No wonder Steno is considered the Father of Stratigraphy.

Obviously Steno was an open-minded and visionary thinker.  And I suspect he wasn't afraid of the unknown ... that he did not feel obligated to fit everything into existing stories, which of course would have limited his amazing thinking.

“Fair is what we see, Fairer what we have perceived, Fairest what is still in veil.”

Modified from source.