<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (May 2009) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (May 2009) (Learn how and when to remove this template message) </Td> </Tr> <P> The Boundary Treaty of 1881 (Spanish: Tratado de Límites de 1881) between Argentina and Chile was signed on the 23 July 1881 in Buenos Aires by Bernardo de Irigoyen, on the part of Argentina, and Francisco de Borja Echeverría, on the part of Chile, with the aim to establish a precise and exact borderline between the two countries based on the uti possidetis juris principle . Despite dividing largely unexplored lands this treaty laid the groundwork for nearly all of Chile's and Argentina's current 5600 km of shared borders . </P> <P> Argentina declared its independence in 1816 and Chile did the same in 1818 . Once the Spaniards had been expelled, relations between the two nations soured primarily due to a border dispute: both claimed to have inherited overlapping parts of Patagonia . </P>

What kind of boundary is offshore the andes mountains