Complex sentence: One of the largest volcanic eruptions of the Holocene epoch is thought to have occurred circa January 1258, with ice cores pointing to a tropical location such as El Chichón, Mexico or possibly Quilotoa, Ecuador.
Split into simpler sentences: One of the largest volcanic eruptions of the Holocene epoch is thought to have occurred ca. January, 1258, with ice cores pointing to a tropical location such as El Chichón, Mexico or possibly Quilotoa, Ecuador.