Evidence of historic infilling of valleys in Lanzarote after the Timanfaya eruption ( ad 1730–1736,Canary Islands,Spain)

Abstract

The Timanfaya eruption (1730–1736) was the most important volcanic event on the Canary Islands during historical times (after the 15th century ad). It produced lava flows and pyroclastic layers that buried around 23% of Lanzarote’s surface. Throughout the island, artificial cross-sections such as soil quarries and road trenches reveal an ash layer covering palaeosoils (argids) or interbedded with alluvial sediment, infilling the bottoms of U-shaped valleys. Five cross-sections located in different parts of the island (Puerto Calero, Femés, Tiagua, Guatiza and Valle de San José) were subjected to sedimentological analyses of colour, texture, carbonate-content and grain-sizes; sand fractions were also studied and finally, mineralogy using x-ray diffraction, and geochemistry (total oxides and trace elements) were applied. These data, along with radiocarbon ages, archaeological remains (pottery) and historical documents, identify the ash layer as part of the Timanfaya eruption. The alluvial sediments covering this layer could have been produced by runoff from heavy rain events, probably the famous Huracán de 1826, also known as the Tormenta de San Florencio.