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A
memorable experience and a spectacle of nature they are considered a wonder of
the world. These falls originated 200 thousands years ago in the place that
today is known as “the 3 frontiers” marked with stone pillars, where the Iguazú
river and the Paraná river meet.
A geological fault produced on the Paraná riverbed made the outlet of the Iguazú
river become an abrupt cascade approximately 80 meters high.
From that point, where the falls originate to where the Devil’s Throat is
located today, covers 23 kilometers. This is due to the slow process of erosion,
however the steep drop which defines them as waterfalls remains.
This original cascade, has become the most impressive falls of the group, The
Devil’s Throat. Eighty meters high, it is located on the principal river course.
Depending on the water level, you can see anywhere between 160 a 260 falls, that
on average flow at a rate of 1500 cubic meters of water per second.
The violence of the falls produce a permanent fog, where sunbeams form multiple
rainbows of incredible beauty.
Three Borders Milestone -
Puerto Iguazú - Argentina
Garganta del Diablo (Devil's Throat) - Parque Nacional Iguazú - Argentina
How
the Iguassu Falls formed?
By Antonio Margalot. From “Geografía de Misiones”.
The regional geology is characterized by the presence of a series of flows.
The term “flows” is the name used to designate volcanic rock that originally
flowed in liquid state under the surface of a solid layer and then cooled
becoming solid.
In the region many of these “flows” have been discovered, 11 distinct ones in
Misiones alone. These flows have successively formed on top of each other
resulting in successive “mantles.” (It is important to note that the term
“mantle” is used incorrectly here. “Mantle” actually refers to something else,
however it will help one not versed in the subject form a mental image).
These “mantles” have very similar physical and chemical properties, but can vary
minutely in composition depending on the cooling process. Consequently, the
erosive action of the falls upon these “mantles” varies as well and some are
eroded faster than others. This is one of the factors responsible for the
formation of Iguazú Falls as it is today.
Another factor is the presence of faults along the course of the river. Faults
are when there is a fracture in in the earth's crust in which the rock on one
side of the fracture has measurable movement in relation to the rock on the
other side.
To visualize the phenomenon imagine a flat, horizontal plane. When a fault takes
place, it creates a “step”, like a stair, that could be a few millimeters to
some meters in size, depending on the intensity of the phenomenon that caused it.
The river slope, in its early phase was quite pronounced and the water “fell”
off of these these steps (faults), having a much more erosive effect than in the
areas without fractures. As a consequence, a depression starts to form
immediately after the fracture.
The Iguassu river runs, at least in some sections, over a flow very resistant to
the erosive action of the water. The layer beneath it, however, is appreciably
more vulnerable to that action. With the passing time the water erodes the lower
layer. With its support removed, the upper layer starts to crumble progressively.
Huge blocks can be observed at the foot of some falls – especially from the
Argentinean side of the Falls – those are the remains of the upper defile. The
previous description explains that the water screen serves as a shelter for
birds and amphibians.
As the erosion process “backwards” continues, over future millenniums the falls
will keep moving, as they have been moving since time immemorial.
Iguaçu Falls - Parque Nacional do Iguaçu - Brazil
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