Iguazu Falls EarthCache
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Iguazu Falls, in Iguazu River, are one of the world's largest waterfalls. They extend over 2.7 km (1.67 miles) in a semi-circular shape. The tallest of the falls is “Devil's Throat” at 82 m (269 ft) in height. Iguazu Falls are on the border between the Brazilian state of Paraná and the Argentine province of Misiones. Two thirds of the falls are within Argentine territory.
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 Iguassu 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 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 millimetres 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 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.
To log this cache you have to complete two tasks.
Task #1: Take a picture of you with your GPS at the given coordinates which point the Devil's Throat (Garganta del Diablo) observation deck at the Argentine side. Make sure that Devil's Throat and GPS are clearly visible in the picture.
Alternatively you can take a picture from the Brazilian side at the coordinates of S 25° 41.461 W 054° 26.216. Take the elevator to observation deck (highest floor where you can go with the elevator) and take a picture of you with your GPS. Make sure that Devil's Throat and GPS are clearly visible in the picture.
Add the picture into your log. Notice that a log without a proper picture will be removed.
Task #2: Answer the two questions presented below.
The Iguazu waterfall system consists of 275 falls (in average). However their number varies depending on the amount of water. When the water is high the number of the falls will be decreased when two or more waterfalls unite as one. This number will also be decreased when the water is so low that there isn’t enough water for all of the falls.
Question 1: Evaluate how many falls there are at the time you visited Iguazu.
Iguazu Falls are surrounded by two National Parks: Iguazú National Park (in Argentina) and Iguaçu National Park (in Brazil). These parks were designated UNESCO World Heritage Sites in 1984 and 1986, respectively. Both are subtropical rainforests that are host to hundreds of rare and endangered species of flora and fauna.
Question 2: What is the total surface area of these two parks?
Please do not answer the questions in your log but send them to cache owner through our profile page. If you don’t send the answers your log will be removed.
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