Apologies in advance - this "article" is going to be quite heavy with quotations from other sources.
Since I am not a Geologist, I need to refer to those who are. I've provided links to all sources, and would encourage you to check them out. I've referred to several articles that are well worth reading in full, if you're interested in getting to the heart of what scientists know about the Grand Canyon and how they reached those conclusions.
Let's dive in...