left|thumb|Algar do Carvão volcanic cave on Terceira Island The islands have many examples of volcano-built geomorphology including caves and lava tubes (such as the Gruta das Torres, Algar do Carvão, Gruta do Natal, Gruta das Cinco Ribeiras), the coastal lava fields (like the coast of Feteiras, Faial, the Mistério of Prainha or São João on Pico Island) in addition to the inactive cones in central São Miguel Island, the aforementioned Capelinhos on Faial, the volcanic complexes of Terceira or Plinian caldeira of Corvo Island. The islands of the archipelago were formed through volcanic and seismic activity during the Neogene Period; the first embryonic surfaces started to appear in the waters of Santa Maria during the Miocene epoch (from circa 8 million years ago).
left|thumb|Algar do Carvão volcanic cave on Terceira Island The islands have many examples of volcano-built geomorphology including caves and lava tubes (such as the Gruta das Torres, Algar do Carvão, Gruta do Natal Gruta das Cinco Ribeiras), the coastal lava fields (like the coast of Feteiras, Faial, the Mistério of Prainha or São João on Pico Island) in addition to the inactive cones in central São Miguel Island, the aforementioned Capelinhos on Faial, the volcanic complexes of Terceira or Plinian caldeira of Corvo Island. The islands of the archipelago were formed through volcanic and seismic activity during the Neogene Period; the first embryonic surfaces started to appear in the waters of Santa Maria during the Miocene epoch (from circa 8 million years ago).