AMD and Mining Environments: Earth’s Early History
Holiday Wishes And A Note Of Thanks
As 2007 draws to a close, Andy and I take this opportunity to thank you, our growing number of subscribers of Abandoned Mine Posts, for your patronage. We both very much enjoy sharing our take on things having to do with abandoned mine reclamation and have been gratified by your positive feedback. We will strive to continue presenting information that is useful in your reclamation efforts in 2008.
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To you and yours, we wish you health and happiness for this holiday season and the coming year.
Bruce Golden and Andy McAllister
AMD and Mining Environments: Earth’s Early History
By Bruce Golden, Regional Coordinator
In this installment of AMD and Mining Environments, we’re going to take a side trip. The chemistry responsible for the formation of abandoned mine drainage is hardly unique to AMD. That same basic chemistry was responsible for transforming our planet’s environment into one friendly to higher life forms, us included, as we’ll see in a very brief account of earth’s early history.
Billions of years ago, the newly formed earth was transformed by a massive infusion of water. One theory has hoards of water-rich comets bombarding a barren, lifeless earth as the origin of the water which ultimately covered the entire planet. Simple single celled life is thought to have had its origins in the depths of this proto ocean.
At that time, the earth’s atmosphere had no oxygen and high levels of carbon dioxide courtesy of volcanism. Undersea volcanic activity was also responsible for creating very high concentrations of iron in an acidic ocean. The water would have been a deep olive green because the iron was in the form of dissolved ferrous ions. And without oxygen, the iron simply remained dissolved. Viewed from our perspective today, the oceans would have been AMD on steroids, and indeed an environment that would have been very hostile to beings such as ourselves.
Over hundreds of millions of years, the first early continents formed. Yeah, volcanoes were involved with this too. In the shallow shore areas blue-green algae appeared in colonies known as stromatolites. Blue-green algae were pioneers of photosynthesis, a process which consumes carbon dioxide and uses sunlight as its source of energy. The waste product of photosynthesis is oxygen. The geologic record shows vast numbers of stromatolites populated these shallows worldwide. Stromatolites produced tremendous quantities of oxygen over vast time periods, eventually and amazingly transforming the earth’s atmosphere into one rich in oxygen, similar to today’s.
As the atmosphere became rich in oxygen, the transfer of oxygen to ocean waters also occurred. Oxygen in turn reacted with the dissolved ferrous iron to form solid iron oxides that settled to the ocean floor. Vast layers of iron rich ores found worldwide are the legacy of this crucial period in the planet’s development. Also, a legacy of that time is blue skies and blue ocean waters, all thanks to oxygen, a product of life.
What the primordial Earth may have looked like.
Illustration courtesy of Case Western Reserve University, Center for Molecular Biology
Note: The History Channel occasionally runs a documentary called “How the Earth Was Formed”. It’s a wonderful introduction for the layman. Watch for it.
December 6th, 2009 at 2:58 pm
Is there any information about this subject in other languages?
December 6th, 2009 at 7:02 pm
My article is a simpified account of what I believe to be a currently held view by many geologists and others who study the origins of eary earth. I’m sure there has to be many sources of such information in other languages. However, I don’t have any specific knowledge of any. Good luck.