GEOLOGICAL MYTHS AND LEGENDS OF THE MAGDALENA & CAUCA RIVER VALLEYS IN COLOMBIA

The author has been carrying out geological research field trips in groups and also, lonely field campaigns.

Objective, to continue presenting information about the Middle Magdalena River Valley (MMRV). At a GSA NC Sec GSA in Madison, WI, photographs of the Higher Terraces on the southern were presented.

Hypothesis on the Tectonic/geological/dynamic forces similarities of both channels and valleys

Methodology, comparing and contrasting some geomorphological, stratigraphic, tectonic features unnoticed by young geologists, although previously planted by earliest field geologists.

Considerations: The valley of the Magdalena River, is taken as the main course of the river with a huge tributary that could well be considered the main tributary river, whose name is Rio Cauca River Valley.

Rio Magdalena and Rio Cauca are born in the same ´Macizo de los Andes´ in Colombia. Both rives move along separate tectonic-structural lineaments and trenches, quasi-parallel from their source in a North to slightly NE direction, for many kilometers. The Cauca River runs parallel West to the Magdalena River, they meet many kilometers North and both become one, they head Northwest to the Caribbean Sea in the Atlantic Ocean.

The Cauca River separates the Western and Central Cordilleras of the Colombian Andes. The Magdalena River separates the Central and Eastern Cordilleras of the Colombian Andes. Both channels have been affected by large landslides since they were dammed; debris flows from the Cordillera Central for both, in different orientations and that geomorphologically produce very high terraces. Example, El Guásimo stopped the Cauca River, in municipalities of the Department of Antioquia, such as Peque´s area and others. The Ibagué Cone stopped the Magdalena River; also, other large landslides around the Tolima Department, such as Lagunilla, Lerida , Armero (where more than 23,000 people died, buried by an initial lahar in the Arenas Volcano covered by perpetual snow called El Ruiz in 1985.

Conclusion, it is necessary to continue establishing geological differences and similarities, since we could have been erroneous for many years about the continental margin during triassic Jurassic and geological importance of these two Valley Rivers.