Deeper into Jeopardy! XXIV: Dinosaurs – $400

This week saw the end of the 2014 Teen Tournament, and congratulations to all its contestants, but extra congratulations to champion Jeff Xie! The end of this week also marks the end of Jeopardy!’s 30th season, which means the third thing it marks is the final official installment of Deeper into Jeopardy! for season 30 (but I’ll still be doing some things around here, so stay tuned). And I can honestly think of no better category to end on than the one I probably would have done best in as a Teen Tournament contestant – plus it has a nice evolutionary link with last week’s category on birds. So, we’ll wrap up the first 24 installments of this new blog series with none other than July 21’s Double Jeopardy! category, DINOSAURS!

Jeopardy! category: DINOSAURS (21-07-2014)

$400 clue: Iridium-rich sediment around the world led to the hypothesis that one of these caused dinosaur extinction

Correct response

The gist: At the north end of Mexico’s Yucatan Peninsula is the site of the impact that eventually killed off the (non-avian) dinosaurs.That’s where you’ll find the Chicxulub (pronounced “chick-shuh-lube”) crater, where a meteor (whether asteroid or comet – no one’s quite sure) exploded about 65 million years ago, causing catastrophic global climate changes and what is now known as the K-Pg or Cretaceous-Paleogene extinction.* The most important change that was caused by the meteor impact was the initiation of an impact winter, which occurs when a major catastrophe throws up a huge amount of dust and other particulate matter, such that light from the sun is unable to reach the Earth’s surface, or reaches it at only a severely reduced rate. Without sunlight, the photosynthesizing organisms that form the base of the food chain nearly everywhere in the world quickly died out, and the resulting cascade of extinctions crept up the food chain: algae, plants, fish, amphibians, small reptiles, all the way up to non-avian dinosaurs. Small bird-like dinosaurs, the descendants of which include all living birds today, were able to survive, because they needed much less food than their bigger cousins and could survive on what little there was. But it was the small rodent-like mammals that really came out on top after the impact – the pattern of mammalian megafauna that we see on Earth today is the direct result of evolutionary niches occupied by the giant dinosaurs having been vacated and refilled by mammals.

The impact was first proposed in the so-called Alvarez hypothesis, named for the father-and-son team of Luis and Walter Alvarez who came up with it. In the 1980’s, the two scientists and their team noticed that the layers of sedimentary rock that divided the age of the dinosaurs in the fossil record from the age that followed was characterized the world over by extremely high concentrations of iridium, an element that’s rare on Earth but abundant in asteroids.

Sedimentary rock showing the K-Pg boundary at the San Diego Natural History Museum – the lighter band in the middle contains about 1000 times more iridium than the darker colours above and below it

The clue: Most everyone knows that a meteor impact is what killed the dinosaurs, so this isn’t a very hard clue. Far fewer people know that iridium concentrations are what led scientists to conclude that it was a meteor impact, so this clue teaches something little-known while asking something well-known. I call that a good clue.

In Jeopardy!: “Meteor” appears in a full 129 regular and four FJ! clue in the J!Archive, which is too many for me to go through – plus, a lot of them are actually about meteorology (“meteor” actually comes from the Greek for “over the air,” i.e. in the sky). Unfortunately, searching for “meteor” and “dinosaur” together returns only three – this one, another one about iridium from 2002, and a category on words ending in “-rite” (for which the correct response was actually “meteorite.” A search for “asteroid” and “dinosaur” gives another six clues (asteroid would almost certainly have been an acceptable response to this clue) – it adds two clues about the Yucatan Peninsula and one where the correct response itself is iridium (it gives the atomic number, 77, as an additional hint). But all in all this isn’t a very hard clue, and I’d be surprised if more than a handful of Jeopardy! contestants don’t know it, so you probably shouldn’t concern yourself with it too much.

*Formerly the K-T or Cretaceous-Tertiary extinction.

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