Geology and Volcanology of Pico Island (Azores, Portugal): A Field Guide

Pico is the biggest island of the Central Group, the second-largest (445 km²) of the Azores archipelago and exhibits the highest point of Portugal (2351 m), the Pico Mountain volcano, which is the 3rd highest volcano of the North Atlantic Ocean. In relation to the surrounding sea-floor Pico Mountain is a 3500 m high polygenetic volcano, characterized by dominant effusive basaltic volcanism episodes of Hawaiian-type eruptions and extensive pahoehoe lava fields. The main geological features of the island are related to the fact that Pico is the youngest island of the archipelago (about 300,000 years old) and its volcanism is almost exclusively of basaltic nature, evident either in the Pico Mountain volcano, the Topo shield volcano or in the volcanic ridge of the Planalto da Achada. This volcanic ridge (e.g., São Roque-Piedade Volcanic Complex) has a length of 30 km and is composed of about 190 scoriae and spatter cones and eruptive fissures. This work outlines the field trip on the Pico Island volcanoes and eruptive history, with emphasis on its main morphotectonics features and geological hazards.