CONSTRUCTIVE AND DESTRUCTIVE EPISODES IN THE BUILDING OF A YOUNG OCEANIC ISLAND, LA-PALMA, CANARY-ISLANDS, AND GENESIS OF THE CALDERA-DE-TABURIENTE

The results of new field observations, 23 new K-Ar determinations and sixteen previously published determinations provide the basis for the reconstruction of the subaerial volcanic history of the island of La Palma, after the seamount activity represented by the materials of the Basal Complex. An eruptive phase between 2.0 and 1.3 Ma formed a large shield. A period of volcanic quiescence followed, until around 1 Ma, during which a large lateral collapse partly destroyed the former edifice. Between 1.05 and 0.7 Ma, activity was renewed in the shield and a N-S ridge was built in the southern part of the island. Around 0.7 Ma, two new large lateral collapses affected the western part of both edifices, and they were followed by eruptions between 0.71 and 0.65 Ma which built a new edifice that partly filled the depressions thus created. The Caldera de Taburiente constitutes the eroded remnants of the depression formed in the northern shield. From 0.65 Ma to present, activity has been restricted to the N-S ridge, which has continued to grow southwards. There was a general N-S migration of volcanic activity with time, but in the shield the trend was northwest to southeast. Eruptive rates seem to have been fairly constant during the different eruptive phases considered, between 0.15 and 0.37 km3/ka. A very similar succession of constructive and destructive episodes has been obtained for the neighboring island of Hierro, but in this case the activity started around 0.8 Ma and eruptive rates were about 0.5 kM3/ka.