Orogeny - Taconic and Berkshire Hills

Our relatively small mountains, shallow valleys, and rolling hills at times dotted with sheep on a sunny fall day show little evidence of the violence of their creation. Almost a half billion years ago mountain rivers deposited sand along the shores of a large, shallow sea at the same time as shell-making animals lived and died by the billions in that sea, their shells soon accumulating in deep carbonate sediments.
As over millions of years the North American continent drifted eastward, it swept up volcanic island arcs that depressed the sand and sediments far beneath rising Taconic mountains that once rivaled the height of Asia's Mt. Everest as our continent collided with the Euro-African continental plate, creating a super continent named Pangaea.
The sand and carbonates of the earlier period were crumpled, folded, and buried to great depths beneath the accumulating continental crust. The heat and pressure soon turned the sand into quartzite and the carbonate sediments into great sheets of limestones of varying thickness and purity. In the early sea's depths, the carbonate sediments were thick and almost unlayered, but near river inflows and coastal erosions into the sea, the resulting limestones alternated between coastal and carbonate sediments, creating many alternating silicon and calcium layers.
Perhaps 275 million years ago, Pangaea cracked, over millions of years widening into the Atlantic Ocean, which continues to widen about two inches a year. With the crack came much erosion followed by several scouring glaciations that carried off much of the Taconics. When the last 5,000-foot-thick glacier melted away some 12,000 years ago, those glaciers had worn most of the Taconics away right down to the ancient carbonate layers commonly found under our silted valleys and grassy knolls.
Today, in western Massachusetts we find remnant beach sand as quartzite and folded limestones in close association, such as this layered limestone bent vertical by ancient geologic forces. As we photographed the pastoral scene above this mute outcrop at our feet spoke volumes.