Celebrating Hispanic Heritage: Walter Alvarez's Contributions to STEM

Eng. Eddier Ovando | Published  October 07, 2022

Walter Alvarez is known for having formulated the theory that the impact of an asteroid extinguished dinosaurs, an idea he developed in collaboration with his father, the physicist and Nobel Prize winner Luis Alvarez.

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Many students are crazy about dinosaurs, and even some of the youngest dinosaur enthusiasts can tell you about the meteorite that ended the reign of the enormous reptiles 66 million years ago. Many years ago, scientists were baffled by what killed off the dinosaurs. This story is widely known today, thanks to Walter Alvarez.

Walter Alvarez was born in Berkeley, California, USA, on October 3, 1940, the son of an immigrant, Luis Alvarez, from Asturias, Spain. His father's scientific career in one of the most prestigious universities in the country inspired young Walter to choose to study geology. He graduated from Carleton University in Minnesota and later earned a doctorate from Princeton.

Later, Walter married and went to work abroad for an oil company, where he lived through the revolution of Muammar Gaddafi. After what happened in Libya, Walter abandoned the oil business and devoted himself to another branch that was beginning to attract much attention, archaeological geology. He moved to Gubbio, Italy, where he started studying how volcanic soils had influenced the Romans' settlement patterns.

On the outskirts of town, Walter and his colleague Bill Lawrie focused their research on analyzing a rock formation composed of dozens of layers of limestone extending for about 400 meters, representing about 60 million years of Earth's geological record. Their analysis included the examination of fossil foraminifera, microscopic organisms. These tiny creatures are ubiquitous in sedimentary rock; however, what was strange about the samples was that, between the layers of limestone, they also found a strip of clay one-centimeter-thick, devoid of any fossils. In addition, they noticed that the foraminifera population in the layers varied considerably from one side of the clay layer to the other. Below the anomalous layer, the foraminifera was abundant; above it, they were scarce. This striking observation was a mystery that was irresistible for a scientific mind like Walter's.

Walter sought help from his father, Luis, with whom he visited sites around the world where they found the same strange rock layer without fossils, but also found that this layer had high concentrations of Iridium, hundreds of times higher than usual.

Iridium is a mineral that is quite rare on Earth but abundant in asteroids. Finding Iridium in large quantities in the same layer worldwide led them to an exciting, almost unbelievable conclusion; millions of years ago, an enormous meteor struck the Earth with catastrophic consequences!

Based on his observations, the Alvarezes postulated in 1980 that the impact of a giant asteroid had created the clay layer with high concentrations of Iridium and that this event of catastrophic proportions was the probable cause of the Cretaceous-Paleogene mass extinction, that event in which 75% of all living beings on the planet died, mainly dinosaurs.

There was only one small problem with Walter's theory, an asteroid of those proportions would have left a massive crater at least 200 km in diameter, and until then, no one had discovered such a crater. In the seventies, geophysicists Antonio Camargo and Glen Penfield, engineers of the parastatal company Petróleos Mexicanos (Pemex), detected a gravimetric anomaly in the Gulf of Mexico while looking for oil deposits. This anomaly had a depth of several kilometers and extended through the Gulf of Mexico and the state of Yucatan. Initially, the engineers did not know what it was, but its shape resembled that of a crater generated by the impact of a meteorite.

In collaboration with NASA, the National Autonomous University of Mexico (UNAM) analyzed the samples of the PEMEX wells to confirm this theory. They determined the dimensions of a crater more than 2.5 km deep and a diameter greater than 200 km, the most giant and best-preserved crater on the planet.

When the Alvarezes learned of this news, they immediately moved to the area to study the concentrations of isotopes of Iridium. They verified that this was the crater they were looking for because of these high levels. This discovery provided a great deal of support for the theory of Walter and Luis Alvarez and today is the theory most accepted by the scientific community.

In 2006 Alvarez began teaching a course at the University of Berkeley titled "Great History: Cosmos, Earth, Life, Humanity." Alvarez's class is open to all levels of academic degrees and seeks to provide a broad understanding of the past, present, and future. Alvarez continues to inspire students, not only because of his genius but also his adventurous spirit and perseverance.


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