Tephra without Borders: Far-Reaching Clues into Past Explosive Eruptions Ponomareva, Vera ; Portnyagin, Maxim ; Davies, Siwan M. Abstract Publication: Frontiers in Earth Science Pub Date: December 2015 DOI: 10.3389/feart.2015.00083 Bibcode: 2015FrEaS...3...83P