The cliffs were once underground channels of molten rock that fed widespread volcanic eruptions 200 million years ago as the supercontinent Pangaea pulled apart at the seams.
In the Midwest a widespread volcanic ash bed, the Pearlette Ash, is an important horizon marker; the Pearlette Ash was probably produced by volcanic eruption in the western Cordilleras.
At a meeting of the Geological Society of America last week, Dr. Keller reported marine fossil evidence that she said linked the mass extinction to widespread volcanic eruptions that swept India at the end of the Cretaceous.
The release of carbon dioxide from widespread volcanic activity associated with the rifting of the supercontinent Pangea, where eastern North America met northwestern Africa, is thought to have strengthened the global greenhouse effect, which raised average air temperatures around the globe and acidified the oceans.
Tephra fall is commonly the most widespread volcanic hazard (Jenkins et al. 2012).
This idea went head to head with another scenario, which argued that widespread volcanic eruptions could release enough gas to alter climate and cause widespread extinctions.
Geologists have long thought these rocks were remnants of lava from an extended period of widespread volcanic activity and that the ancient supercontinent split much later.
Another possible scenario to explain the widespread volcanic conduits is that the arc volcanoes themselves have been migrating trenchward over time.
Tephra falls, referred to colloquially, and throughout this paper, as ash falls, are one of the most widespread volcanic hazards (e.g. Magill and Blong, 2005).
The earliest, mid-Ordovician, records of plant spores coincide with these widespread volcanic deposits, suggesting the possibility of a genetic relationship.
