Final answer:
The largest lake in Chile and the 4th largest in Argentina that lies on their shared border is Lake General Carrera/Lake Buenos Aires, well-known for its scenic Patagonian landscapes and importance to biodiversity and tourism.
Step-by-step explanation:
The largest lake in Chile and the 4th largest in Argentina, which is situated on their border, is Lake General Carrera in Chile and Lake Buenos Aires in Argentina.
This is a binational lake, as it is known by different names depending on the country. This region is characterized by the Patagonian landscapes and its large glaciers, providing scenic beauty and essential water resources that feed into various streams and rivers in the surrounding areas.
Lake General Carrera/Buenos Aires is an important natural asset for both countries, boasting not only significant size but also contributing to the biodiversity and economic activities such as tourism. The region's varied topography, including areas like the Atacama Desert, the Andes Mountains, and the unique Patagonia, displays the environmental diversity shared between Chile and Argentina.