 That night , two herdsmen near the site heard a continuous roar , punctuated by loud bangs and crackling sounds " like that of great rockslides " . Lightning and thunder accompanied the spectacle . They saw many blue flames , and were choked by sulfurous gas . Observers in Talca 85 kilometers ( 53 mi ) away heard the eruption noises , and the sulfurous odors reached them the day after the eruption . None of the reports mention earthquakes or ash fall , though the crackling and banging sounds could be from block lavas ( ʻaʻā ) . 
