One of the most significant early events of the early Excessions was the Athabasca Incident. The exact causes are now lost, although the suggestion of Durst that supernatural events were involved seems highly unlikely, given the technological nature of pre-Excession Canadian civilization.
What is known is that quite rapidly, a large area of what was then the northern Great Plains became completely uninhabitable. At distances greater than 100 miles from the then city of Athabasca, Alberta the disasters were of a normal nature-widespread plagues, firestorms, massive earthquakes. Inside of that circle, however, considerably stranger events occurred. Invisible forces wracked the very fabric of reality, objects disappeared or became utterly strange, most humans went swiftly insane. 
Within 25 miles, the effects are unknown. To this day, a black churning cloud surrounds the area, penetrating deep below the surface of the earth, and extending in a dome several miles overhead. No technological means have been able to penetrate this force, no human has ever entered it and returned. A primary goal of the Sagittarius Initiative has been to find ways to enter the zone. The theories of this group, and in particular Malachi Kawasaki's ideas of transdimensional rifts, are ridiculous.
- Mystic Influences in Pre-Disaster Cultures
- Evidence for effects on non-humans is less clear. See Aykroyd and Ramis for further detail.