Gerta Keller

Last updated
Gerta Keller
Born7 March 1945
Schaan, Liechtenstein
CitizenshipSwitzerland, Liechtenstein, United States [1]
Alma mater San Francisco State University (B.S.)
Stanford University (Ph.D.)

Gerta Keller (born 7 March 1945) is a geologist and paleontologist whose work has focused on global catastrophes and mass extinctions. She has been a professor of geosciences at Princeton University since 1984 and received emeritus status in July 2020. [2] Keller contests the mainstream Alvarez hypothesis that the impact of the Chicxulub impactor, or another large celestial body, directly caused the Cretaceous–Paleogene extinction event. Keller maintains that such an impact predates the mass extinction and that Deccan volcanism and its environmental consequences were the most likely major cause, but possibly exacerbated by the impact. [3] [4] Considered a leading authority on catastrophes and mass extinctions, including the biotic and environmental effects of impacts and volcanism, Keller is one of few scientists whose work has consistently supported the contention, with nearly half of her 300 publications being articles which address the asteroid impact/volcano controversy [5]

Contents

Early life and education

Keller was raised in Switzerland on a dairy farm, the sixth of 12 children. She grew up in poverty. In the one-room schoolhouse where she was educated, boys were given training in math and science while girls were taught cooking and cleaning, the skills they would need to be proper housewives. Her hunger for knowledge led her to read the textbooks assigned to her elder siblings, and she would prepare summaries of the material for her brothers and sisters. [6]

She attended a vocational school starting at age 14 and learned sewing. There she organized a protest against rules that required female students to wear skirts, as she rode her bicycle three miles each way to school and wanted to be able to protect herself from the cold. The female students won the right to wear pants from then on.

After receiving her vocational certificate at age 17, she went to work for Pierre Cardin, where she was paid the equivalent of 25 cents per hour to sew luxury gowns that would sell for as much as $1,000 for which she was paid $12. She traveled around the world, learning English and working in England, followed by travel to North Africa, Spain and Australia. She survived being shot in a bank robbery in Australia in 1965, despite awakening in a hospital intensive care unit to find a priest pressing her to confess, telling her that she was going to die. [6] [7]

After ending up in San Francisco in 1968, Keller was "freaked out" by the shots and tear gas launched at student protests; she chose to focus on education and took a high school equivalency exam. She received her undergraduate degree at San Francisco State University and received a doctorate in geology and paleontology from Stanford University in 1978.

Paleontology

After earning her doctorate, Keller worked for the United States Geological Survey and Stanford. [6] She came to Princeton University in 1984 and after a few years started studying the Cretaceous–Paleogene boundary (K–T boundary), the geological signature of the Cretaceous–Paleogene extinction event. [8] Keller's research has led her to conclude that the Chicxulub asteroid impact, the leading hypothesized cause for the Cretaceous–Paleogene extinction event, [9] predates the event to the degree that it could not have been the sole cause. "I'm sure the day after, they had a headache," Keller states, further stating that "we vastly overestimate the damage to the environment and to life that this Chicxulub impact had". [10]

The main evidence for the Alvarez hypothesis that the Chicxulub impact resulted in the Cretaceous–Paleogene extinction event, supported by earth sciences consensus, [9] comes from the presence around the world of shocked quartz granules, glass spherules and tektites embedded in a layer of clay with extremely high levels of iridium, all signs of an asteroid impact. Keller's research found layers where the glass spherules and the iridium clay are separated by as much as 8 feet (2.4 m) of sandstone and other material. Supporters of the Alvarez hypothesis have concluded that the sandstone is the result of a massive tsunami caused by the Chicxulub impact that sandwiched the sand between the shocked quartz layer and the iridium clay. Keller's analysis of the strata between the spherules and iridium clay concludes that the material was laid down over as much as 300,000 years based on signs of plankton, worms and weathering found on the intervening material. [11]

Bestowed the title of Doctor Honoris by The University of Lausanne, Switzerland (2022) for her major contributions to the mass extinction controversy of the Cretaceous-Tertiary period, Keller has received countless recognitions in her field of scientific work. This includes the 2012 Radhakrishna Prize for research on Deccan volcanism linked to the end-Cretaceous mass extinction, among various other distinguished fellowships, honors and awards. [12]

Selected publications

Related Research Articles

<span class="mw-page-title-main">Deccan Traps</span> Large igneous province in India

The Deccan Traps are a large igneous province of west-central India. They are one of the largest volcanic features on Earth, taking the form of a large shield volcano. They consist of many layers of solidified flood basalt that together are more than about 2,000 metres (6,600 ft) thick, cover an area of about 500,000 square kilometres (200,000 sq mi), and have a volume of about 1,000,000 cubic kilometres (200,000 cu mi). Originally, the Deccan Traps may have covered about 1,500,000 square kilometres (600,000 sq mi), with a correspondingly larger original volume. This volume overlies the Archean age Indian Shield, which is likely the lithology the province passed through during eruption. The province is commonly divided into four subprovinces: the main Deccan, the Malwa Plateau, the Mandla Lobe, and the Saurashtran Plateau.

<span class="mw-page-title-main">Chicxulub crater</span> Prehistoric impact crater in Mexico

The Chicxulub crater is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is offshore, but the crater is named after the onshore community of Chicxulub Pueblo. It was formed slightly over 66 million years ago when an asteroid, about ten kilometers in diameter, struck Earth. The crater is estimated to be 200 kilometers in diameter and 1 kilometer in depth. It is believed to be the second largest impact structure on Earth, and the only one whose peak ring is intact and directly accessible for scientific research.

<span class="mw-page-title-main">Impact winter</span> Hypothesized climate effects due to an asteroid or comet impact on Earth

An impact winter is a hypothesized period of prolonged cold weather due to the impact of a large asteroid or comet on the Earth's surface. If an asteroid were to strike land or a shallow body of water, it would eject an enormous amount of dust, ash, and other material into the atmosphere, blocking the radiation from the Sun. This would cause the global temperature to decrease drastically. If an asteroid or comet with the diameter of about 5 km (3.1 mi) or more were to hit in a large deep body of water or explode before hitting the surface, there would still be an enormous amount of debris ejected into the atmosphere. It has been proposed that an impact winter could lead to mass extinction, wiping out many of the world's existing species. The Cretaceous–Paleogene extinction event probably involved an impact winter, and led to mass extinction of most tetrapods weighing more than 25 kilograms.

<span class="mw-page-title-main">Walter Alvarez</span> American geologist (born 1940)

Walter Alvarez is a professor in the Earth and Planetary Science department at the University of California, Berkeley. He and his father, Nobel Prize–winning physicist Luis Alvarez, developed the theory that dinosaurs were killed by an asteroid impact.

<span class="mw-page-title-main">Chicxulub Pueblo</span> Town in the Mexican state of Yucatán

Chicxulub Pueblo is a town, and surrounding municipality of the same name, in the Mexican state of Yucatán.

A verneshot is a hypothetical volcanic eruption event caused by the buildup of gas deep underneath a craton. Such an event may be forceful enough to launch an extreme amount of material from the crust and mantle into a sub-orbital trajectory, leading to significant further damage after the material crashes back down to the surface.

<span class="mw-page-title-main">Réunion hotspot</span> Volcanic hotspot in the Indian Ocean

The Réunion hotspot is a volcanic hotspot which currently lies under the island of Réunion in the Indian Ocean. The Chagos-Laccadive Ridge and the southern part of the Mascarene Plateau are volcanic traces of the Réunion hotspot.

The Shiva crater is the claim by paleontologist Sankar Chatterjee and colleagues that the Bombay High and Surat Depression on the Indian continental shelf west of Mumbai, India represent a 500-kilometre (310 mi) impact crater, that formed around the Cretaceous-Paleogene boundary. Chatterjee and colleagues have claimed that this could have contributed to the K-Pg extinction event. Other scholars have questioned the claims, finding that there is no evidence of an impact structure.

<span class="mw-page-title-main">Alvarez hypothesis</span> Asteroid impact hypothesis as cause of the Cretaceous–Paleogene extinction

The Alvarez hypothesis posits that the mass extinction of the non-avian dinosaurs and many other living things during the Cretaceous–Paleogene extinction event was caused by the impact of a large asteroid on the Earth. Prior to 2013, it was commonly cited as having happened about 65 million years ago, but Renne and colleagues (2013) gave an updated value of 66 million years. Evidence indicates that the asteroid fell in the Yucatán Peninsula, at Chicxulub, Mexico. The hypothesis is named after the father-and-son team of scientists Luis and Walter Alvarez, who first suggested it in 1980. Shortly afterwards, and independently, the same was suggested by Dutch paleontologist Jan Smit.

<span class="mw-page-title-main">Maastrichtian</span> Sixth and last age of the Late Cretaceous

The Maastrichtian is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from 72.1 to 66 million years ago. The Maastrichtian was preceded by the Campanian and succeeded by the Danian. It is named after the city of Maastricht, the capital and largest city of the Limburg province in the Netherlands.

The term iridium anomaly commonly refers to an unusual abundance of the chemical element iridium in a layer of rock strata at the Cretaceous–Paleogene (K–Pg) boundary. The unusually high concentration of a rare metal like iridium is often taken as evidence for an extraterrestrial impact event.

<span class="mw-page-title-main">Cretaceous–Paleogene boundary</span> Geological boundary between time periods

The Cretaceous–Paleogene (K–Pg) boundary, formerly known as the Cretaceous–Tertiary (K–T) boundary, is a geological signature, usually a thin band of rock containing much more iridium than other bands. The K–Pg boundary marks the end of the Cretaceous Period, the last period of the Mesozoic Era, and marks the beginning of the Paleogene Period, the first period of the Cenozoic Era. Its age is usually estimated at 66 million years, with radiometric dating yielding a more precise age of 66.043 ± 0.043 Ma.

The Lopez de Bertodano Formation is a geological formation in the James Ross archipelago of the Antarctic Peninsula. The strata date from the end of the Late Cretaceous to the Danian stage of the lower Paleocene, from about 70 to 65.5 million years ago, straddling the Cretaceous-Paleogene boundary.

The climate across the Cretaceous–Paleogene boundary is very important to geologic time as it marks a catastrophic global extinction event. Numerous theories have been proposed as to why this extinction event happened including an asteroid known as the Chicxulub asteroid, volcanism, or sea level changes. While the mass extinction is well documented, there is much debate about the immediate and long-term climatic and environmental changes caused by the event. The terrestrial climates at this time are poorly known, which limits the understanding of environmentally driven changes in biodiversity that occurred before the Chicxulub crater impact. Oxygen isotopes across the K–T boundary suggest that oceanic temperatures fluctuated in the Late Cretaceous and through the boundary itself. Carbon isotope measurements of benthic foraminifera at the K–T boundary suggest rapid, repeated fluctuations in oceanic productivity in the 3 million years before the final extinction, and that productivity and ocean circulation ended abruptly for at least tens of thousands of years just after the boundary, indicating devastation of terrestrial and marine ecosystems. Some researchers suggest that climate change is the main connection between the impact and the extinction. The impact perturbed the climate system with long-term effects that were much worse than the immediate, direct consequences of the impact.

<span class="mw-page-title-main">Cretaceous–Paleogene extinction event</span> Mass extinction event about 66 million years ago

The Cretaceous–Paleogene (K–Pg) extinction event, also known as the K–T extinction, was the mass extinction of three-quarters of the plant and animal species on Earth approximately 66 million years ago. The event caused the extinction of all non-avian dinosaurs. Most other tetrapods weighing more than 25 kg (55 lb) also became extinct, with the exception of some ectothermic species such as sea turtles and crocodilians. It marked the end of the Cretaceous period, and with it the Mesozoic era, while heralding the beginning of the current era, the Cenozoic. In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, Fatkito boundary or K–T boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows unusually high levels of the metal iridium, which is more common in asteroids than in the Earth's crust.

<span class="mw-page-title-main">Timeline of Cretaceous–Paleogene extinction event research</span> Research timeline

Since the 19th century, a significant amount of research has been conducted on the Cretaceous–Paleogene extinction event, the mass extinction that ended the dinosaur-dominated Mesozoic Era and set the stage for the Age of Mammals, or Cenozoic Era. A chronology of this research is presented here.

Vivi Vajda is a Swedish palaeontologist. She is Professor and head of palaeobiology at the Swedish Museum of Natural History.

Alan Russell Hildebrand is a Canadian planetary scientist and Associate Professor in the Department of Geoscience at the University of Calgary. He has specialized in the study of asteroid impact cratering, fireballs and meteorite recovery. His work has shed light on the extinction event caused by the Chicxulub asteroid at the end of the Cretaceous period. Hildebrand is one of the leaders of the Prairie Meteorite Network search project.

Dinosaurs: The Final Day with David Attenborough is a British documentary programme that aired on BBC One on 15 April 2022. Presented by David Attenborough, the documentary follows the final days of non-avian dinosaurs through the Cretaceous–Paleogene extinction event.

<span class="mw-page-title-main">Chicxulub Puerto</span> Coastal town in Progreso Municipality, Yucatán, Mexico

Chicxulub Puerto is a small coastal town in Progreso Municipality in the Mexican state of Yucatán. It is located on the Gulf of Mexico, in the northwestern region of the state about 8 km east of the city port of Progreso, the municipality seat, and 42 km north of the city of Mérida, the state capital. According to the INEGI census conducted in 2020, the port town had a population of 7,591 inhabitants.

References

  1. ↑ "Gerta Keller, Professor of Geosciences, Emeritus: Volcanism, Impacts and Mass Extinctions". Princeton University . Retrieved May 21, 2022.
  2. ↑ "Gerta Keller". Princeton.edu. The Trustees of Princeton University. Retrieved 5 February 2024.
  3. ↑ "The Dissenter". Archived from the original on 6 February 2016. Retrieved 5 December 2012.
  4. ↑ "Massive volcanoes, meteorite impacts delivered one-two death punch to dinosaurs" . Retrieved 5 December 2012.
  5. ↑ "Gerta Keller". Princeton.edu. The Trustees of Princeton University. Retrieved 5 February 2024.
  6. 1 2 3 Hedges, Chris (17 December 2003). "PUBLIC LIVES; Where Dinosaurs Roamed, She Throws Stones". The New York Times. Retrieved 5 December 2012.
  7. ↑ Stone, Richard (2014). "Back from the dead". Science. 346 (6215): 1281–1283. doi:10.1126/science.346.6215.1281. PMID   25504698.
  8. ↑ Schultz, Steven. "Dinosaur dust-up: Princeton paleontologist produces evidence for new theory on extinction", Princeton Weekly Bulletin , September 22, 2003. Accessed June 11, 2009.
  9. 1 2 Schulte, P.; et al. (2010). "The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary" (PDF). Science . 327 (5970): 1214–1218. Bibcode:2010Sci...327.1214S. doi:10.1126/science.1177265. PMID   20203042. S2CID   2659741.
  10. ↑ Velasquez-Manoff, Moises. "Did Asteroids Really Do in the Dinosaurs?: Scientists Challenge the Story of How the Dinosaurs' 160-Million-Year Reign Came to an End", ABC News , May 24, 2009. Accessed June 11, 2009.
  11. ↑ Lovett, Richard A. "'Dinosaur Killer' Asteroid Only One Part of New Quadruple-Whammy Theory", National Geographic , October 30, 2006. Accessed June 16, 2009.
  12. ↑ "Awards and Recognitions". Princeton.edu. © In 2022 the Trustees of Princeton University. Retrieved 5 February 2024.
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