What Is the Sima Humboldt Sinkhole in Venezuela?

What Is Sima Humboldt?

Sima Humboldt is a massive natural sinkhole in Venezuela, plunging 314 metres straight down into the quartzite plateau of Sarisariñama, with a completely isolated forest at the bottom that has evolved its own unique species found nowhere else on Earth.

Where Is Sima Humboldt Located?

Sima Humboldt sits atop the Sarisariñama tepui — a flat-topped sandstone and quartzite mesa deep in the Venezuelan jungle, in the Jaua-Sarisariñama National Park in Bolívar State. There are no roads or trails leading to it. Every scientific expedition has required a helicopter just to reach the rim. The tepui itself rises above the surrounding jungle like a lost island in the sky, and the sinkholes carved into its surface are among the most geologically unusual features on the planet.

How Deep Is the Sima Humboldt Pit?

The pit drops 314 metres — roughly the height of a 100-storey building — with walls that are essentially vertical. That sheer geometry is what makes Sima Humboldt so extraordinary. There is no slope, no scree, no gradual descent. The walls simply fall straight down, and they are smooth enough to make any natural entry or exit nearly impossible. This vertical isolation is the key to everything that makes the sinkhole scientifically remarkable.

The Secret Ecosystem at the Bottom

Because the walls are unclimbable and the pit is sealed from the surrounding jungle, the forest at the bottom has been cut off from the outside world for thousands of years. Plants, insects, and other organisms have been evolving in complete isolation inside this rocky chamber. When scientists were lowered in by helicopter, they discovered plant species that exist nowhere else on the planet — endemic flora that had quietly diverged from their ancestors across millennia of solitude. The ecosystem at the base of Sima Humboldt is, in the truest sense, a lost world.

The Second Sinkhole: Sima Martel

Just 700 metres away from Sima Humboldt sits a second enormous pit — Sima Martel, nearly 248 metres deep. This is not a coincidence of geography so much as a feature of the underlying geology; the quartzite cap of the Sarisariñama tepui has been dissolved from below over vast timescales by slightly acidic rainwater percolating through cracks, eventually collapsing to form these colossal chambers. What makes the proximity of Sima Martel so scientifically tantalising is the possibility that its isolated ecosystem evolved entirely independently from Sima Humboldt’s — two separate biological experiments running simultaneously, side by side, separated by less than a kilometre.

Why Sarisariñama Tepui Is So Rare

Tepuis are among the oldest geological formations on Earth, with some rock dating back nearly two billion years. They have long been recognised as biodiversity hotspots — their isolated summits act like biological islands, accumulating endemic species over millions of years. Sarisariñama is unusual even among tepuis for hosting these vertical sinkholes, which add yet another layer of isolation within an already isolated landscape. The sinkholes are carved into quartzite rather than limestone, which is the rock type associated with most sinkholes worldwide, making the Sarisariñama pits geologically distinctive as well as biologically extraordinary.

How Much of Sima Humboldt Has Been Explored?

Very little. The extreme remoteness of the site, the requirement for helicopter access, and the logistical difficulty of descending into a vertical 314-metre shaft mean that most of the sinkhole’s interior remains scientifically unstudied. The species inventories compiled from the few expeditions that have reached the bottom are almost certainly incomplete. Sima Humboldt is one of those rare places on Earth where genuine biological discovery remains not just possible but likely.