Pico #3: Gruta das Torres

Grutas das Torres (tower caves) is a lava tube cave, or lava tunnel, on Pico Island. It is the longest lava tunnel in all the Azores.

What is a Lava Tunnel?

Here is how a lava tunnel is formed:

A volcano erupts and lava flows out of the volcano.
As the lava flows, the outer layer is exposed more to the air, which cools and hardens it, forming a top layer of crust.
Meanwhile, underneath the upper layer of solid crust, the lava continues to flow underneath.
Eventually, the lava supply diminishes and drains away, leaving behind an empty tube, or cave.
An entrance to the tunnel naturally opens when a piece of the surface above the tunnel collapses.

7,998,050 BCE: The formation of Santa Maria, the oldest island of the Azores
298,050 BCE: The emergence of Pico Island
450 AD / CE: The formation of Gruta das Torres
1460: The first settlement of Pico Island
1720: The last volcanic eruption on Pico Island
1990: The first scientific expedition of Gruta das Torres
2004: Gruta das Torres is classified as a Regional Monument
2005: Gruta das Torres opens to the public