Today’s Wonder of the Day was inspired by Adela from Hamilton. Adela Wonders, “Why did dinosaurs become extinct?” Thanks for WONDERing with us, Adela!

Have you ever seen the movie Jurassic Park? Wouldn't it be cool if you could visit a theme park to see real dinosaurs today? Better yet, how awesome would it be if you could travel to certain areas of the world to see real dinosaurs still living in the wild?

We can't do any of these things, of course, because all the dinosaurs are gone. (Well, some scientists believe that modern birds are the living ancestors of dinosaurs, but that's for another Wonder of the Day!)

Based upon the fossils of dinosaurs found around the world, scientists believe that all the dinosaurs — along with thousands of other plant and animal species — died off in a mass extinction event around 65 million years ago.

What could have caused such a catastrophic destruction of species? That's the question that many scientists have been searching for an answer to for many years. Today, there are two main hypotheses that scientists believe might explain what occurred.

The most popular theory is that Earth was hit by a giant asteroid, comet, or meteorite about 65 million years ago. Scientists developed this theory because they found a layer of the element Iridium, which is rare on Earth but plentiful in space, that dates back to when the dinosaurs went extinct.

For years, though, they were unable to find evidence of such an impact on Earth. Then, in 1991, scientists discovered the Chicxulub crater, which is a massive 110-mile wide crater that sits along the edge of Mexico's Yucatán Peninsula and extends out into the Gulf of Mexico.

To form such a crater, scientists believe the asteroid, comet, or meteorite would've had to have been at least six miles wide and hit Earth at a speed of about 40,000 miles per hour. Such an impact would've released about two million times more energy than the most powerful nuclear bomb.

The heat from the impact would have scorched Earth's surface, starting fires worldwide while at the same time blotting out the Sun as debris filled the atmosphere. Humongous tsunamis would have flooded large parts of the world. Shock waves could have triggered massive earthquakes and volcanic eruptions.

The darkness could have lasted for months and even years, interrupting the process of photosynthesis and plunging the Earth into a deep freeze. Eventually, greenhouse gases trapped in the atmosphere could've then caused another wild swing in worldwide climate, leading to the mass extinctions that occurred.

The other popular theory is similar to the asteroid theory. It holds that a huge increase in volcanic activity in what is now India led to similar clouding of the atmosphere with similar effects on photosynthesis and weather.

Some scientists believe that it's possible that both theories are partially correct and may have occurred simultaneously or that an asteroid impact could've set off the volcanic activity that made the worldwide impact even worse.

Of course, it's impossible to test such theories…and who would want to trigger another mass extinction anyway? Some scientists still hold other views and prefer other theories. As long as there remains an interest in dinosaurs, scientists will continue to search for fossils that may shed light on what exactly happened 65 million years ago!

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