Geology Reference
In-Depth Information
million years represents an infinitesimal portion of eternity. Theologians were starting to
waver on a six-thousand-year-old Earth.
As the idea that geologic time involved more than a few thousand years became reas-
onable, Abraham Werner, a charismatic professor at the Freiberg Mining Academy, began
popularizing the idea that the rocks revealed that earth history consisted of four periods.
Werner's father, a Saxon foundry inspector, had passed on to his son a keen interest in min-
erals, and at the age of twenty-five Werner published an influential field guide that landed
him a professorship at the Freiburg School of Mines. Five years later he offered the first
course in historical geology. A gifted lecturer, Werner's influence grew as his students du-
tifully spread his ideas about geologic history across Europe.
A lab man who wanted to understand earth history from the study of minerals and rocks
without all the bother of fieldwork, Werner adopted Buffon's view that our planet formed
when a stray comet smashed into the Sun, spinning off a fireball that slowly cooled to be-
come covered by a universal ocean. He proposed that the primary (crystalline) rocks pre-
cipitated from this global sea, accounting for marine fossils found high in mountains. Nep-
tunists, as Werner's disciples were known, attributed deposition of the secondary (layered)
rocks to material settling slowly to the bottom of the drying sea. They saw the signature of
Noah's Flood in the sculpting of topography, and the deposition of the tertiary rocks that
were made of gravel, sand, and clay derived from erosion and redeposition of the primary
and secondary rocks. On top of all this was a fourth, or quaternary, level of unconsolidated
sand and gravel eroded off uplands by running water, like the deposits of modern rivers.
In short order, these four divisions were found to adequately describe the rocks of other
mountain ranges, like the Apennines and Caucasus.
As this crude geological system began to formalize the basis for evaluating the thickness,
lateral extent, and relative age of rock formations, it became apparent that irregular bound-
aries (unconformities) separated geological eras. And yet individual layers within the sec-
ondary rocks could be traced across Europe. Delicate layers just a few centimeters thick
could be traced across tens of kilometers, something impossible to attribute to a chaotic de-
luge that ripped apart and mixed up the world's surface in the way that Burnet and Wood-
ward had imagined. Werner's dominant influence on geological thinking meant that layered
