The Perito Moreno Glacier is one of the few active glaciers in the world and the only one advancing in Patagonia. This advance is generating another  phenomenon of shocking beauty: the breaking of the dam that forms in the Rico arm channel of Lake Argentino. The glacier touches the shore and forms a dam that stops the passage of water. Then the water seeps under the glacier and begins to undermine its base. The National Park Los Glaciares (where Perito Moreno Glacier stands) was declared heritage of mankind by the UNESCO, 30 years ago.