Sunday Sciku | The Great Unconformity

Here’s something I’d never heard of: The Great Unconformity. The Grand Canyon is like a timeline of earth’s history, with each layer going back farther in time as you descend its walls, all the way back to rock that formed 1.8 billion years ago at the bottom.

The only problem is that a billion years worth of rock is missing. The timeline jumps from the Tonto group of 700 million years ago to the Vishnu basement layer 1.6 billion years ago. Geologist John Wesley Powell was first to discover this way back in 1869, but still no one really knows what happened to all that rock.

There are several competing theories, apparently, and they all likely played some role. For example, rock layers were weathered away by ice during the snowball earth period.

Geologists at the University of Colorado, though, published work this week providing thermochronological evidence for what seems to be the primary cause.

During the breakup of the first Pangea supercontinent, the western end of the Grand Canyon region was lifted so high that the basement layer came to the surface, but it was still miles underground at the eastern end.

The whole North American plate seems to have tipped like a saucer as Rodina split apart, and millions of years of rock slid into the sea.

 

basement rock
exposed at the surface
the great divorce

 

Sunday SciKu | AMOC

The Atlantic Meridional Overturning Circulation is the conveyor belt that transports warm water from the tropics northward and cold water south, balancing the heat distribution in the Northern Hemisphere and allowing for the relatively mild temperatures in Europe. New evidence has emerged this week from the Potsdam Institute providing further evidence that the AMOC is undergoing a loss of dynamic stability and may be on the verge of collapse.

The culprit is climate change, as lighter freshwater from melting land glaciers accumulates on the surface of the ocean, reducing the sinking action that drives this circulatory current.

The new report made headlines, but few seem to be providing the details about what this could mean for our future. The triggers of abrupt climate change in the paleo record remain a mystery, but the leading hypothesis is that these Dansgaard-Oeschger oscillations are related to changes in the AMOC. What seems to happen is that this fresh meltwater from a warm period sitting on the surfaces of the northern oceans causes this current to stall, which make temperatures in the Arctic plummet. Because freshwater freezes at higher temperatures than saltwater, this surface layer leads to an increase in sea ice, increasing the polar albedo, making the temperatures in the Arctic even colder, creating a feedback loop with cooling progressing southward toward the equator.

Another factor at play is the Beaufort Gyre, a clockwise-swirling current in the Arctic Ocean that traps cold freshwater. Historically, the gyre has reversed every 5-8 years or so, releasing that cold down into the North Atlantic, but the reversal is now a full 8 years overdue, and it’s holding more freshwater than all of the Great Lakes. When the reversal finally comes, it will release even more cold freshwater into the North Atlantic, sending Europe into a freeze and adding to the problem of the stalling AMOC. The effect is large enough that researchers have called the Beaufort Gyre a “ticking time bomb“—one that’s still ticking 4 years later.

The most extreme example of what an AMOC collapse can do may be the Younger Dryas, where temperatures rapidly fell 10 °C in Greenland and 5 °C Great Britain. With human-released CO2 tipping the scales in the opposite direction, no one really knows what’s going to happen. But it’s long been my opinion that it was this sudden climactic shift that drove the mammoths and mastodons to extinction, along with 70% of the rest of North American megafauna, and not human predation. The situation reminds me of this 19th century drawing of all the mammoth tusks from Siberia sitting on the trading docks in London. To me, it looks like Hokusai’s The Great Wave.

 

a frozen ocean
mammoth tusks
for sale

 

Sunday SciKu | Prenatal Oneironauts

This week, researchers at Yale monitored retinal waves in the brains of mice to show that they were dreaming visually before birth, practicing the use of sight so they would be prepared for possible predators the moment they open their eyes.

Newborn humans exhibit some of the same behaviors, so this is believed to imply that fetuses dream as well. What’s interesting, though, is the question of what the dreams would be. Some kind of ancestral, epigenetic memory of sight?

 

morning fog
an infant dreams
in the womb

 

Sunday Haiku | The Chicken or the Egg

One of several great things about the new mRNA vaccines is that they’re so simple. They’re basically just the lipid membrane, saltwater, and the mRNA, which is so easy to synthesize that I did it myself as an undergrad. Despite all the rumors, there are far fewer opportunities for side-effects and unknowns than with traditional vaccines.

Unknowns like this. For years, flu researchers at the Wilson Lab at the University of Chicago kept seeing antibodies that were reactive to every virus they tested, and they couldn’t figure out why. It turns out the antibodies were binding to glycan, a sugar molecule found in the chicken eggs that the vaccines were being produced in.

The early polio vaccines were grown in monkey kidney cells, and about a quarter of them turned out to be contaminated with Simian Virus 40, which may increase the risk of soft-tissue cancers (still a controversial claim to this day)—so we started growing vaccines in chicken eggs instead. Almost 50 years later, we just realized this process leads to the production of antibodies for glycan.

As this is a new discovery, we don’t know what it means, if it means anything, but it’s easy to imagine that this has been making all of our egg-grown vaccines less effective than they would be otherwise, as the immune system wastes resources making antibodies to these meaningless clumps of sugar.

The point is, biology is messy and traditional vaccines are a crude technology. That we’re advancing to mRNA vaccines, with much less junk and much greater precision, is something to celebrate.

.

 

light’s long journey
from the sun into the son
eggs over-easy

 

Sunday SciKu | Evaporative Stress

Photo by Cristina Anne Costello via Unsplash


Another old axiom proves true: Stress really does turn your hair gray—and a relaxation can reverse it.

In this study out of Columbia University, researchers used a new technique to make ultra-fine slices through strands of hair, looking back in time the same way climatologists study ice cores. Each slice, 1/20th of a millimeter thick, represents about an hour of hair growth. They then compared changes in pigmentation to psychological stress recorded in the subjects’ diaries.

Grayness increased on stressful days. Moreover, one of the subjects went on vacation during the study, and the gray growth completely reversed over that period.

The researchers investigated more closely and found that these differences corresponded to changes in proteins related to mitochondrial function—our cellular energy factories. Evidence that mitochondria respond to psychological stress has important implications for the study of aging, which we do a lot of this time of year in the western woods.

 

dry summer
all the fuel in the foothills
going gray