{"id":2151,"date":"2026-08-17T07:48:29","date_gmt":"2026-08-17T05:48:29","guid":{"rendered":"https:\/\/etnahiker.it\/pit-crater-sulletna-i-crateri-che-nascono-sprofondando\/"},"modified":"2026-08-17T10:40:11","modified_gmt":"2026-08-17T08:40:11","slug":"pit-craters-etna","status":"publish","type":"post","link":"https:\/\/etnahiker.it\/en\/pit-craters-etna\/","title":{"rendered":"Pit Craters on Etna: the craters that form by collapsing"},"content":{"rendered":"\n\n\n

When we picture the crater of a volcano, the image is almost always the same: an explosion firing ash and lapilli into the sky, carving a hollow at the top of the mountain. On Etna, however, there are craters formed in exactly the opposite way \u2014 not because something was pushed out, but because the support beneath gave way and the ground sank. These are pit craters<\/strong>, or collapse craters<\/em>: shafts with vertical walls that open in silence and reveal what is happening inside the conduit, tens of metres below.<\/p>\n\n

It is neither a rare nor a distant phenomenon. In recent days, during the eruptive phase of August 2026<\/strong>, a pit crater has again become clearly visible at the base of the North-East Crater<\/strong>: a structure our guides watch closely, because it is quite literally a window onto the inside of the volcano.<\/p>\n\n

In this article we look at what a pit crater is, how and why it forms, how it differs from an explosive crater<\/strong> and how to recognise one while walking the high-altitude trails of Etna.<\/p>\n\n

\n \"A\n
The pit crater seen from the rim: the shaft sinks into the flank of the cone, with no raised rim at all around the opening.<\/figcaption>\n<\/figure>\n\n

What is a pit crater<\/h2>\n\n

A pit crater<\/strong> is a circular or elliptical depression with steep, vertical walls<\/strong>, formed on the surface of a volcano. The English name describes its shape well: a clean shaft, often sheer, that opens in the ground without building anything around itself.<\/p>\n\n

The difference from a classic volcanic crater lies entirely in its origin. An explosive crater is excavated from the inside out, and around the vent it piles up the pyroclastic material thrown into the air by the eruption: that is why it has a raised rim<\/strong>. A pit crater does not. It is born from a structural collapse<\/strong>, a downward failure. Its edges therefore stay flat, level with the surrounding ground.<\/p>\n\n

The distinction may sound technical, but it completely changes the meaning of what you are looking at. An explosive crater tells the story of an eruption that happened; a pit crater tells the story of a void<\/strong> that formed at depth.<\/p>\n\n

How and why a pit crater forms<\/h2>\n\n

A collapse crater forms in three stages.<\/p>\n\n

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  1. Emptying of the subsurface.<\/strong> A cavity forms beneath the surface of the volcano. This can happen when a lava tube drains at the end of an effusive eruption, when a magma chamber deflates after erupting, or when magma migrates sideways along fissures and dykes, abandoning the section of conduit it occupied.<\/li>\n
  2. Fracture propagation.<\/strong> With the support of the magma gone, the overlying rock \u2014 the “roof” of the cavity \u2014 has to bear its own weight alone. Gravitational stress generates vertical fractures that propagate progressively upwards, until they approach the surface.<\/li>\n
  3. Gravitational collapse.<\/strong> At that point the rock mass fails and collapses downwards into the void. What remains at the surface is a deep shaft, with almost perfectly vertical walls and, as noted, no raised rim.<\/li>\n<\/ol>\n\n

    The collapse may happen all at once or, more often, through successive failures<\/strong>: the pit widens over time, eating away at its own walls, and can change in diameter and depth within a few weeks.<\/p>\n\n

    How to recognise a pit crater on Etna<\/h2>\n\n

    If you are walking Etna’s high-altitude trails \u2014 or those of any other basaltic volcano, from Hawaii to R\u00e9union \u2014 three clues let you identify a pit crater at a glance.<\/p>\n\n