 The volcano, whose most recent activity dates to 1943 and last major eruption around 3600 years ago, overlies the Eocene El Bosque Batholith, dated at 49.1 ± 1.7 Ma.The steep-sided, glacier-clad Nevado del Tolima volcano contrasts with the broad profile of Nevado del Ruiz to the north.The andesitic-dacitic younger Tolima formed during the past 40,000 years, rising above and largely obscuring a wide Late Pleistocene caldera.