Ribbon Falls is a beautiful waterfall within the The Grand Canyon that’s roughly an 8 mile hike from the North Rim. After walking a short distance off the North Kaibab Trail through a narrow side canyon with towering walls of quartzite on both sides of you, the falls make a dramatic appearance:
This splendid pool and shower of cool water was truly an oasis in the dry hot canyon that easily reaches over 100ºF in temperatures; and for or us it was the perfect place to take a siesta during the heat of the day.
What makes Ribbon Falls visually and geologically interested is that huge 30 ft tall moss covered mound of rock that sits directly underneath the falls. In this high energy location where the water hits the ground you might expect erosional forces to dominate but instead deposition reigns here. This is a massive travertine deposit. Travertine is essentially limestone (aka calcium carbonate) that’s deposited by fresh water instead of sea water. As Ribbon Falls Creek passes over one of the many limestone units upstream it dissolves calcium carbonate and then deposits them at Ribbon Falls.
Our rivers and creeks are by no means pure H2O but a mixture containing a multitude of different ions floating around just waiting to bond with one another. In solution calcium, carbon, and hydrogen atoms often bond to form the soluble compound calcium bicarbonate, Ca(HCO3)2 , but given the right pressure and temperature conditions a precipitation reaction occurs and calcium bicarbonate reacts to form the insoluble compound calcium carbonate.
Ca(HCO3)2(aq) → CO2(g) + H2O(l) + CaCO3(s)
In our case the right conditions occur once the water flowing out of Bright Angel Falls comes into contact with the ground thus precipitating it’s calcium and carbon ions. Over time this accumulation has simply built up to for form the mound that we see today
How long did it take for this dome to build up? That’s a great question! As far as I can tell no one has calculated this. I would take an interval of time (such as a year), measure the accumulation rate for that period, determine the size of the dome, and then do the math. Would anyone reading this like to pay for me to go back to The Grand Canyon in the name of science?