Chicxulub crater

The Chicxulub crater is a giant impact crater buried under the Yucatán Peninsula in Mexico. It was made a little over 66 million years ago when an asteroid about ten kilometres wide hit Earth.

The crater is roughly 200 kilometres across and lies about a kilometre below younger rocks. Scientists now widely accept that the impact and its climate effects were the main cause of the mass extinction that ended the age of the non-bird dinosaurs. Because the crater is buried, you cannot see it from a window; it was found by studying gravity and rocks. It is one of the largest impact structures on Earth.

How was it discovered?

In the late 1970s, geologist Walter Alvarez and his father, physicist Luis Alvarez, found a thin clay layer rich in iridium, an element rare on Earth but common in asteroids. They argued it was dust from a huge impact.

Around the same time, geophysicists Antonio Camargo and Glen Penfield, searching for oil in Yucatán, noticed a strange circular structure. In 1990 Penfield received rock samples that showed it was an impact crater, matching the Alvarez idea.

What did the impact do?

The impact date matches the end of the Cretaceous period, when about 75 per cent of plant and animal species disappeared, including all dinosaurs except birds.

Evidence includes shocked quartz, a gravity anomaly and glassy droplets called tektites in surrounding areas. The crater is also special because its peak ring, a ring of hills made during the impact, is intact and can be studied.

On the globe

Find it on the globe on Mexico's Yucatán Peninsula and zoom in to open its card.