EXPLORETY

Why Dinosaurs and Ammonites Vanished – and Why It’s Important Today

About 65.5 million years ago, the Cretaceous-Tertiary extinction event, called the K-T event, took place, killing dinosaurs and other animals that roamed the Earth at the time.

The idea that a catastrophic event drastically changed Earth’s climate and geology was first proposed by a Russian scientist, Joseph Shklovsky, in 1956, who thought it had been a supernova with a resulting radiation shower. But why did some animals survive? A father-and-son team, Luis and Walter Alvarez, proposed in 1981 that an asteroid or meteor hit the planet. They discovered iridium deposits in Italy; a crater located later in the Chicxulub Crater in Mexico also seemed to support the theory.

Disrupted food supply

Working backwards, scientists determined that the crater was formed by a collision with an object that was approximately 6 miles in diameter and traveling 40,000 mph at the time it collided with Earth. The heat it likely released would have sent shockwaves throughout the planet in the form of wildfires, tsunamis, volcanic eruptions and earthquakes.

What’s more, debris from a blast of this magnitude would have blocked Earth’s atmosphere. Without sunlight and with dropping temperatures, the food supply – plants eaten by the herbivores – would have been severely disrupted. Herbivore dinosaurs would have died first, followed by the carnivores, whose food supply was predominantly the herbivore animals and other carnivores.

Other theories are still abundant. Some propose that a plague wiped out the dinosaur population; others that dinosaurs became too big for their brains to handle. The climate change theory was prevalent for years, claiming that the lower temperatures from the North and South poles would have caused the temperatures to drop too significantly for the dinosaurs to survive. And while there is some evidence for the theory – such as 65-million-year-old lava flows found in India, the abrupt disappearance of so many species makes the theory less likely.

Fit for survival?

Smaller mammals – those that lived in aquatic environments and underground burrows -- were better equipped to escape the temperature spike caused by the meteor strike, as well as the subsequent food shortages, “nuclear winter” with its cold temperatures and debris-filled atmosphere, and a reduction of oxygen in the water.

Mosasaurus: lizard of the Meuse River

Since they didn’t require nearly as much food as dinosaurs, many were able to survive on the minimal plant and animal life that remained. Among them are crocodiles and alligators, lizards and turtles, snakes and mammals and, of course, birds.

The demise of the prehistoric sea creatures

Not all sea creatures survived the K-T event: along with dinosaurs, ammonites, coil-shelled sea monsters that are most closely related to cephalopods such as squid and octopuses, vanished forever.

More than 10,000 ammonite species once existed in every part of the planet, including Antarctica. The fossilized helix-shaped shells are particularly important for archeologists, as they contain clues about climate conditions millions of years ago.

Ranging from a few inches to nine feet in size, ammonites glided through every sea on Earth, hunting for food. Unfortunately, the biggest source of their food was marine plankton, which became scarce in the immediate aftermath of the K-T event. According to another theory, ocean acidification dissolved the shelves of the young ammonites early in their lifecycle.

There is no meteor that currently poses a threat to Earth, but many of our actions are directly responsible for climate change and the subsequent ice melt, rising sea levels, and ocean acidification. As a result, the delicate balance of ecosystems around the globe gets disrupted and species become extinct: in fact, there are almost 2,500 animal species currently categorized as critically endangered by the International Union for Conservation of Nature. Responsible travel and volunteer trips may not be the total solution, but it is most definitely a part of it.

Did you know?

  • When the Alvarez team first published their findings about the cause of dinosaur extinction, they were ridiculed by many in the scientific community for a theory that seemed too far-fetched. Today, it is the predominant theory of dinosaur extinction.

  • In medieval Europe, ammonites were known as snakestones or serpent stones because they were believed to have been left behind by snakes. Alleged to have healing powers, they were believed to provide evidence for the existence of saints such as Saint Patrick. Similarly, in Nepal, they were called shaligrams, icons representing the existence of the Hindu god Vishnu.

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