Sunday, June 13, 2010

Why is there so much marble in Vermont, anyway?

The other day, I got a chance to use those credits in Geoscience. Never underestimate how useful any knowledge can be.

My sister-in-law was talking about buying marble countertops, purchased from Vermont. This should tell you something about my sister-in-law right there, a woman that prides herself on all the cliches of upper middle class McMansion ownership - you can take the girl out of Jersey, but...!

And she wistfully wondered, rhetorically if not expecting an answer, why there is so much marble in Vermont anyway.

Lucky for her I did a ton of projects on the stratigraphy and history of New England, so to her astonishment there actually is an answer.

Here it is in a nutshell:

Marble is a metamorphic carbonate rock, which means it was originally one type of rock that became another. Take some underwater sedimentary deposits, like limestone, which is mostly CaCO3, and is extremely water-soluble,. Now, as limestone was deposited by sedimentary action on the ancient continetal shelf, a range of volcanic mountains came close and the heat and pressure forced the limestone to crystallize. Because limestone contains various other materials inside it, these impurities form the distinctive coloring and swirls that add to marble's distinctive look.

This all happened during an event in the Cambrian, called the Taconic Mountain Building Event, around 500-470 million years ago, when New England formed because of the closing of a shallow sea lined with volcanic islands....the two ingredients to create marble deposits. There are even some limestone deposits that weren't sufficiently metamorphosed and didn't crystallize, and remain carbonate rocks.

By the way, the Taconic Mountains I'm describing here no longer exist anymore and have nothing to do with the modern-day Taconic Mountains; we only know of their former existence through geologic clues. The modern-day Taconic Mountains actually pushed up the tip of the old, worn-down ancient Taconics.

For a little bit of perspective on how huge a scale geologic time operates, 500-470 million years ago, there was absolutely zero land-life, mostly because the atmospheric composition of the atmosphere was such that anything that tried to live on land would have been cooked by ultraviolet rays. Likewise, at this point in history, there were no creatures with a backbone that would be the ancestors of vertebrates, except at the very end. The Ordovician, which comes at the tail end of this development, is also called "the Age of Fishes."

This is actually not that huge compared to some other mineral deposits. Heck, Minnesota's state gem, the Lake Superior Agate, on average formed about a billion years ago!

(The process of mountain-building is called Orogeny. If you want to do Geology, you gotta speak the lingo. For my fellow lovers of Greek myth and culture, Oreads are the rarely-seen Mountain Nymphs, which has the same root. It goes to show how a little Greek never hurt anybody!)

Usually, I try to have some moral here, something we can learn that's bigger than just the science, and I guess it's this: part of intellectual curiosity means never assuming a question is unanswerable. My sister-in-law probably didn't appreciate me being pushy and volunteering this information, but the point is an answer existed for the question that she had.

No comments:

Post a Comment