Faial's geosites: the Caldeira, the Pedro Miguel graben, the Capelo ridge and Costado da Nau

Faial is a small island, 21 kilometres long, and most of its geology is on show. The Azores Geopark names six geosites on the island, numbered FAI 1 to FAI 6, and all of them can be seen from a road, a viewpoint or a short path. In order, they show how the island was built: an old volcano in the east, broken by faults, a big central volcano with a crater at the top, and a line of young cones running west to the newest land in the Azores.

This guide goes through them one by one: what each one is, and where to stand to see it. You do not need any geology. Three words help. A tuff cone is a volcano built by an eruption in shallow sea water, when the steam blasts the lava into ash. A graben is a strip of land that has dropped between two faults. A scoria cone is the ordinary small cinder volcano you see all over the Azores.

The Geopark's own list, with its numbers:

• FAI 1: the Caldeira
• FAI 2: the Graben de Pedro Miguel
• FAI 3: Monte da Guia
• FAI 4: Morro do Castelo Branco
• FAI 5: the Capelo peninsula
• FAI 6: Capelinhos volcano and Costado da Nau

The list on the Geopark website also has three empty slots, FAI 7 to FAI 9, marked "in development" with no names yet. None of the six charges entry. The only ticket on the way is the Capelinhos interpretation centre, which is optional.

The Caldeira is the collapsed summit of the central volcano that makes up most of Faial. It is about 2 kilometres across and about 400 metres deep, and it is a nature reserve. Inside it, the Geopark points out a small pyroclastic cone, a lava dome and a lake. The lake has come and gone since 1958, when the Capelinhos eruption at the other end of the island set off steam explosions inside the crater too.

Where to look: drive to the end of the road and walk through the short tunnel to the viewpoint. The rim trail PRC04FAI starts there, 6.8 kilometres round, about two and a half hours, between 840 and 1,040 metres, and it passes close to Cabeço Gordo, the island's high point at 1,043 metres. The crater is often in cloud, and cloud up there can clear in minutes or not at all, so go early and be ready to wait or turn back. The crater floor is closed to walkers on their own: you can go down only with a Faial Nature Park guide, and the park allows 40 visitors a day. Our guide to Capelinhos and the Caldeira covers the rim walk.

East of the Caldeira the land drops in steps towards the sea. This is the Pedro Miguel graben, which the Geopark calls the island's main volcano-tectonic structure and the most impressive one in the Azores. The faults run west-north-west to east-south-east, the same line as the Capelo ridge, and they have broken the old shield volcano of eastern Faial into a staircase. The Ribeirinha area at the far end is the oldest part of the island, about 800,000 years old.

This end of the island still shakes. The earthquake of 9 July 1998 hit it hardest. It put out the Ribeirinha lighthouse, opened in 1919, for good, and wrecked the parish church of São Mateus.

Where to look: the Ribeiro Seco viewpoint on the regional road in Ribeirinha looks over the headland and the lighthouse ruin, with Pico, São Jorge and Graciosa across the water. To see the steps themselves, walk them: the trail PR07FAI, Caminhos Velhos, climbs 17.5 kilometres from Ribeirinha up the graben to the Caldeira. It is graded hard and takes about seven hours. Our Faial coast-to-coast guide covers it as the first of two days.

The headland that closes Horta's Porto Pim bay to the south is a tuff cone, from an eruption under the sea. It has two craters, both open to the sea on the south side and flooded. A strip of dunes with the Porto Pim beach on it joins it to the island, together with Monte Queimado, a small scoria cone at the Horta end. It is about 145 metres high and is classified as a special protection area.

Where to look: walk up. The Entre Montes circuit, PRC08FAI, is 3.4 kilometres from the Porto Pim beach car park, easy, and passes the chapel of Nossa Senhora da Guia, finished in 1943, at the top. From there you look down into the flooded craters on one side and over Horta on the other. The opening of the craters, the Boca das Caldeirinhas, is a dive site; the inside of the crater is protected and access is restricted. Our diving guide has the details.

On the south coast near the airport, a rounded block of pale rock sticks out into the sea on a narrow neck of land. It is a trachyte dome: thick, sticky lava that piled up instead of flowing. Pumice from the Caldeira volcano covers it, and the sea has cut its sides into high cliffs. The top has weathered to white clay, which is where the name comes from, "white castle".

It is a nature reserve of about 16 hectares, 149 metres at the highest point, and Cory's shearwaters nest in the cliffs from March to October. They fly in from the sea at dusk.

Where to look: the trail PRC05FAI starts at Lombega on the regional road, 3.7 kilometres, about an hour and a half. The Castelo Branco harbour and bathing area below gives the side view of the cliffs from sea level.

West of the Caldeira, Faial narrows into a ridge 8 kilometres long, running west-north-west like the faults at the other end. About 20 young scoria cones line it up, with their lava flows, all from the Holocene, the last 12,000 years or so. Two of them have names you will see on signs. Cabeço do Fogo is the vent of the 1672-73 eruption, which did its worst damage in Praia do Norte. Cabeço Verde has the Furna Ruim beside it, a pit 55 metres deep.

Where to look: Cabeço Verde has a road to the top, and from there the cones run away from you east to west in a line, ending at Capelinhos, with Praia do Norte, Cabeço do Fogo and Morro do Castelo Branco around you. The short trail PRC01FAI, Cabeço do Canto, starts near the access road: 2.5 kilometres, about two hours, past the edge of the Furna Ruim and the Algar do Caldeirão. Keep back from the edge of the pit, and take care crossing the red and black lapilli road. Down on the north coast, at the beach and harbour of the Fajã da Praia do Norte, the black lava from the 1672 eruption is studded with green olivine. These are pieces of the Earth's mantle the magma carried up. The Ribeira das Cabras viewpoint above the fajã looks along the coast to Capelinhos.

The full ridge is a walk of its own: PR06FAI, the Ten Volcanoes trail, runs 19.3 kilometres from the Caldeira viewpoint down to Capelinhos, graded hard, about five hours.

Capelinhos is the last cone on the ridge and the youngest. The eruption started in the sea off the old Capelinhos islets on 27 September 1957 and went on for 13 months, to 24 October 1958. It began under the sea, like Monte da Guia, and turned into a land eruption as the new cone grew. It added about 2.4 square kilometres to Faial.

The reason the Geopark pairs it with Costado da Nau is that the cliff next to the new land shows the same sequence in an older eruption. Costado da Nau is a fossil sea cliff, deeply eroded, and its layers record a volcano that also started under water and finished on land. From the foot of the new cone you can look across at the old cliff and compare the two.

Where to look: the interpretation centre is built underground next to the half-buried lighthouse. In 2026 it opens daily from 10:00 to 18:00 from April to October, and Tuesday to Saturday from 09:00 to 17:00 from November to March; adults pay €10, juniors aged 7 to 14 and seniors €5, a family €20. Check the Nature Park site before you go. You do not need a ticket to walk onto the ash slopes or look at Costado da Nau from the road. The old whale lookout on the cliff is a ruin; stay out of it and off the cliff edge.

By car, all six fit into one day if the weather is kind. Two ways to order it:

• Clear morning: the Caldeira first, while the summit is free of cloud, then west along the Capelo ridge with a stop at Cabeço Verde, Capelinhos and Costado da Nau around midday, back along the south coast past Morro do Castelo Branco, and Monte da Guia from Horta in the evening light.
• Cloudy morning: start at the coast, with Monte da Guia and Castelo Branco, and drive up to the Caldeira only if the cloud lifts. Finish in the east at the Ribeiro Seco viewpoint over the graben.

Our round-island drive covers the roads, viewpoints and villages in between.

How many geosites does Faial have? Six with names, FAI 1 to FAI 6. The Geopark website lists FAI 7 to FAI 9 as well, still in development and unnamed.

Do the geosites cost anything? No. They are open landscapes and viewpoints. The only charge is the optional Capelinhos interpretation centre, €10 for an adult in 2026.

Can you walk into the Caldeira? Only with a Faial Nature Park guide, and only 40 people a day may go down. The rim walk needs no guide or permit.

Which geosite is best if I have only two hours? From Horta, Monte da Guia: the Entre Montes circuit is 3.4 kilometres from Porto Pim and shows a tuff cone from the inside and the outside.