text: Periodically the glacier advances over the L-shaped `` Lago Argentino '' ( `` Argentine Lake '' ) forming a natural dam which separates the two halves of the lake when it reaches the opposite shore .
simplified: Periodically the glacier advances over the L-shaped `` Lago Argentino '' ( `` Argentine Lake '' ) . when it reaches the opposite shore , it forms a natural dam which separates the two halves of the lake .