Iguazu Foz- Geologic Formation

For who may be interested...

 

The visual, natural wonder that is Iguaçu Foz was created by a river flowing over multi-tiered ancient lava flows.  The rocks that form the walls of the falls and the riverbed above and below are basaltic rocks.  The reason the falls are so wide (over a mile) is because the river widens out significantly about 18 km upstream of the falls.  It has cut many smaller channels in the basaltic rock much like a river delta.  Each individual channel creates its own waterfall of which there are over 280 in the official count.  Of course the number of waterfalls at any one time is dependent on the volume of water in the river at the moment.  More water would tend to flood the individual channels and create more massive but more consolidated waterfalls.  Lower water volumes would tend to highlight the number of individual water falls up to a point where the lack of water would dry up the falls.  In the hostel, there was a very neat picture showing the falls when the water level was at a 10-year low (a mere 185 m^3/s)  and when the water level was at a 10-year high (a massive 22,200 m^3/s).  The difference was very dramatic.

 

We intend on visiting Victoria Falls in Africa later in our trip.  We have Wikipedia'd information on waterfalls and learned that Victoria Falls lie on top of ancient basaltic lava flows

also.  The Wikipedia article has a good comparison of the characteristics of the various waterfalls around the world like Niagara, Iguaçu, and Victoria.

 

Next is Sao Paulo...

 

Sean