The Chicxulub crater and cenotes

Quick facts

• Age: about 66 million years old, the same time as the dinosaur extinction.
• Size: about 180 km (some estimates up to 200 km) wide.
• Centre: near the coastal town of Chicxulub Puerto, north of Mérida.
• Depth: buried under about 1 km of younger limestone (reported).
• Asteroid: about 10 km wide (reported).

How it was discovered

Geophysicists working for the Mexican oil company Pemex noticed a huge buried arc in 1978. In 1980 Luis and Walter Alvarez proposed that an asteroid caused the mass extinction, based on iridium in rock layers. In 1991 scientists linked the buried Yucatán structure to that impact. In 1996 researchers reported that the semicircle of cenotes matched the crater's buried rim (reported).

Did the impact create the cenotes?

No. Cenotes form when rainwater dissolves limestone, and they exist all over the peninsula and around the world. The impact created the Chicxulub structure, which shaped where the densest band of cenotes sits.

How the crater shaped the Ring of Cenotes

• The impact fractured the rock along the crater rim.
• Younger limestone settled over it, leaving weak zones above the rim.
• Groundwater flows faster along these fractures, dissolving more rock.
• The result is an arc of cenotes about 180 km wide, from near Celestún through Homún to near Dzilam.

Why it matters for water

The ring behaves like a big underground channel that steers groundwater toward the coast. That makes it important for Mérida's water supply. Yucatán state protects it as a Geohydrological Reserve of the Ring of Cenotes, and Mexico submitted it to UNESCO's tentative World Heritage list (UNESCO).

Can you visit the crater?

• There is nothing visible to see at Chicxulub Puerto itself, only a small sign and plaque.
• The Museo del Meteorito (Science Museum of the Chicxulub crater) near Mérida explains the impact (reported).
• The best way to 'see' it is to swim in cenotes on the ring, such as those in Homún, Cuzamá and Sacalum.

Cenotes on the ring

• Homún: Santa Bárbara, Hool Kosom and many family cenotes.
• Cuzamá: Chelentún, Chacsinicché and Bolonchoojol by horse cart.
• Sacalum: Sabak-Há and others to the south.
• See our Ring of Cenotes guide.

The impact, in numbers

About 66 million years ago an asteroid around 10 km wide struck what is now the northern Yucatán. It left a crater about 180 to 200 km across, now buried under roughly 1 km of younger limestone. The impact is linked to the mass extinction that ended the non-avian dinosaurs.

Did the asteroid create the cenotes?

Not directly. The cenotes formed much later, as rainwater dissolved the limestone that settled over the crater. The buried crater rim changed the rock and groundwater flow, which is why so many cenotes line up in an arc above it.

The Ring of Cenotes today

The semicircle of cenotes is clearly visible on maps and runs through towns such as Homún, Cuzamá and Dzilam. The area has been proposed for UNESCO recognition, and its cenotes are a protected groundwater reserve for Mérida and nearby towns.

Where to see it

There is no visible crater on the surface. Swim in ring cenotes in Homún or Cuzamá to see the trace of the impact for yourself.