Chicxulub crater

The Chicxulub crater is a huge impact crater hidden under the Yucatán Peninsula in Mexico. It got its name from a small village called Chicxulub Pueblo, not the bigger coastal town Chicxulub Puerto. About 66 million years ago, a giant asteroid, roughly ten kilometers or six miles wide, crashed into Earth and created this crater. Today, the crater is about 200 kilometers or 120 miles wide but is covered by about a kilometer or 0.62 miles of rock.

Two scientists, Antonio Camargo and Glen Penfield, found the crater while they were searching for oil in the late 1970s. At first, they couldn’t prove it was a crater, but later, with help from Alan R. Hildebrand, they gathered evidence showing it was caused by an impact. They found special shocked quartz, changes in gravity, and small glass-like rocks called tektites around the area.

This impact happened right at the end of a time period called the Cretaceous–Paleogene boundary. Many scientists believe the huge explosion and changes in climate from this event caused a big mass extinction. About 75% of all plants and animals, including the non-avian dinosaurs, disappeared from Earth because of it.

Discovery

In the late 1970s, geologist Walter Alvarez and his father, a scientist who won a special prize, suggested that a big event caused many plants and animals to die out at the end of the time called the Cretaceous. They found a thin layer of clay with a lot of a special material called iridium, which is rare on Earth but common in space rocks. This made them think a space rock had hit Earth.

Later, geophysicists Glen Penfield and Antonio Camargo found signs of a big crater under the Yucatán Peninsula in Mexico while they were looking for oil. They shared their ideas, but many scientists did not pay attention at first. Years later, scientist Alan Hildebrand learned about Penfield’s work and, with others, confirmed the crater’s existence. They named it after a nearby town, Chicxulub Pueblo. Today, scientists agree that this huge space rock hit Earth and caused many species, including the dinosaurs, to go extinct.

Impact specifics

A study from 2013 found that the impact happened about 66 million years ago. They used different ways to measure the time, like looking at rocks from Haiti and Montana. Another study in 2015 checked rocks from Montana and got a similar answer. A third study in 2018 looked at rocks from Colombia and found a slightly different time.

At the time of the impact, the place where it hit was under the sea. The water was deep, and the ground had layers of different kinds of rocks. The object that hit Earth was about ten kilometers wide—bigger than Mount Everest!

The energy from the impact was huge, like setting off many, many bombs. It made very strong winds and huge waves in the ocean. These waves moved sand and dirt far away. The blast also threw up a lot of dust and hot air, which spread around the world. This caused fires and made it very dark for a long time. The change in climate affected plants and animals everywhere. Even far away, many living things died suddenly. The dust in the air blocked sunlight for years, making the Earth very cold and dark. This hurt the plants and the animals that depended on them. Over time, the place where it hit became a place where people could live, even though there wasn’t much water on the surface.

Post-discovery investigations

Geophysical data

Scientists have studied the area under the ocean near the crater using special sound waves. These waves help them see deep underground. They first collected data in 1996, and then again in 2005, using boats and land stations to record the sound. This helped them learn more about the shape and structure of the crater.

Borehole drilling

Researchers also took samples from deep holes drilled into the ground. Some of these holes were originally made to look for oil. In 1995, scientists drilled several holes on land. In 2001 and 2002, they drilled a deep hole near a place called Hacienda Yaxcopoil. In 2016, they even drilled a hole deep into the ocean floor, getting samples from the very center of the crater.

Morphology

The Chicxulub crater has a special ring-like shape. Scientists learned about its structure mainly through special imaging methods. The biggest ring is far from the center and marks where the Earth's surface was pushed down. This ring is one of the largest of its kind on our planet.

Closer to the center, there is another ring called the main crater rim. Between this rim and an inner ring called the peak ring is an area with tall rock blocks. The peak ring itself is quite large and stands above the rest of the crater in some places. These rings are clearest in some areas because of how deep the water was when the asteroid hit.

Geology

Before the asteroid hit Earth, the area of the Yucatán area was made up of layers of limestone, with older rocks called red beds underneath. These rocks are part of a larger land area known as the Maya Block, which was once near the edge of an ancient continent called Gondwana.

After the asteroid struck, special kinds of rocks formed from the impact, called suevites. These rocks were moved and reshaped by water flowing back into the crater. Deep inside the crater, there are also rocks formed from melted material, which came from the Earth's crust during the impact.

Over time, new layers of limestone and other rocks built up over the crater, and today, you can still see signs of the impact in the land and underground water systems of the Yucatán peninsula.

Astronomical origin and type of impactor

Scientists believe the object that created the Chicxulub crater was a type of asteroid called a C-type asteroid, made of materials found in carbonaceous chondrites. These asteroids usually form far from Earth, beyond the planet Jupiter.

In the past, some researchers thought the impactor might have been a comet from a distant area called the Oort cloud. However, studies show there was too much iridium — a rare element — spread around the world for it to have been a comet. The evidence points strongly to the impactor being an asteroid, not a comet.