Each week, I devote part of my Sunday to reading. I tend to accumulate a lot of saved links on Facebook during the week, and I like to try to keep up with what fellow writers are posting here on WordPress. At the end of my reading day, I like to put up a post to draw my readers’ attention to a few articles I found to be of particular interest.
Here’s what I enjoyed this week:
by Laurel Hamers, Science News
Normally, I try to vary the subject matter of articles I share on Reading Day, but this week I’ve chosen a theme. Over the past few weeks, science news has been inundated with new research regarding the Cretaceous extinction event. The first of these articles I’m sharing this week concerns, as Science News’s Laurel Hamers puts it, the climate “roller coaster ride” our planet went through in the aftermath of the event.
As most everyone knows, the Cretaceous period, and indeed the age of the dinosaurs, came to a thrilling end 66 million years ago when an asteroid 10-15 kilometers in diameter hit the Yucatán, leaving a 200 kilometer wide crater. The impact set off massive tsunamis and triggered global wildfires that decimated Earth’s forests, while subsequent out-gassing pumped vast quantities of sulfur dioxide into the atmosphere. The resulting impact winter deprived Earth’s surface of sunlight for decades, killing off most life on the planet.
While the initial destruction has been well-understood for years, a new research project headed by paleogeologist Ken McLeod of the University of Missouri in Columbia has shed new light on the more long-term effects of the impact. In the lab, McLeod and his colleagues analyzed a jumble of crushed fish remains, including bones, teeth, and scales, left behind in the wake of the catastrophe. The oxygen ratios in the remains show that, following the impact winter, Earth experienced a period of intense global warming due to massive amounts of carbon dioxide being released into the atmosphere. This raised global temperatures by up to five degrees Celsius (a staggering spike), producing a warming trend that persisted for roughly 100,000 years.
by Katherine Kornei, Science Magazine
In this second article, Science Magazine’s Katherine Kornei details the findings of a recent study showing, as one researcher put it, “how resilient life can be”.
In an effort to understand how life returns to impact craters, in 2016 a research team drilled down into the Chixulub impact crater, retrieving hundreds of sediment cores. Chris Lowery, a paleoceanographer at the University of Texas Institute for Geophysics, led an analysis of the cores, focusing on the fine grains of sediment that made up the limestone samples. Amazingly, the researchers discovered fossils, as well as burrows left by worms, deep in the sediment.
Thus, it would appear that life returned to the crater in a matter of years. The researchers speculate that the key to this sudden resurgence of life may have been the crater’s structure. Unlike craters like the Chesapeake Crater, left in Virginia by an impact roughly 35 million years ago, the Chixulub Crater was partially open to the Gulf of Mexico. This would have allowed a flow of nutrient-rich seawater into the crater, likely flushing out toxic minerals and allowing life to return.
by John Pickrell, National Geographic
As part of their “Year of the Bird”, National Geographic produced an article asking how some birds of the Cretaceous period managed to survive the devastation of the Chixulub impact. As Nat Geo’s John Pickrell writes, the answer rewrites our understanding of the evolution of modern birds.
Among the most well-known elements of the impact’s aftermath is a series of global firestorms that decimated Earth’s forests. According to research led by Daniel Field at the University of Bath, however, the damage might have been far more complete than previously believed. Field’s team suggests that in the wake of the impact, primitive avian birds were completely wiped out, while most modern birds are descended from smaller, ground-dwelling species (the ancestors of modern chickens, geese, and ostriches).
The almost complete disappearance of avian species suggests that Earth’s forests may have been completely, or almost completely destroyed. This suggestion is supported by fossil spore records, which suggest that ferns experienced a boom following the impact event. Researchers believe this “fern spike” is an example of so-called Disaster Flora: adaptable species that quickly recolonize ruined areas following a natural disaster.
The researchers say that it may have been thousands of years before mature forests returned to Earth, and even after they did, their composition was forever changed.
Knowledge is power. Take time out to read a bit every day. It’s your window into the world around you. – MK