Category Archives: Musings & News

The Eye Of The Sahara

The Eye of the Sahara as seen from the International Space Station (photo from Wikimedia Commons)

While looking for something else I found … this beautiful eye of stone. It’s so large that it’s best seen from outer space, as shown in a photo from the International Space Station.

The Eye of the Sahara or the Richat Structure is embedded in the Adrar Plateau near Ouadane, Mauritania. It’s 25 miles across — the distance from Pittsburgh to Greensburg — so people couldn’t see its unusual shape until we could fly above it.

When photos came back from the Gemini space missions in the 1960s, the geologists went to work. At first they thought it was a meteor impact crater but meteors leave evidence behind and “the critical rock types failed to reveal a single feature attributable to shock processes. We, therefore, dismiss an impact origin for this structure. It must, instead, be endogenic.

Endogenic means “formed below the earth’s surface.” Indeed the Richat structure is a geologic dome, a magma bubble that hardened before it broke the surface then eroded away to expose the bubble’s onion-like layers. The youngest rock is on the outer edge, the oldest — 600 million years old — is in the center. The rust, blue, and white colors are the different kinds of rock.

Diagram from video showing how the Richat Structure formed (click here to see the video by Jeffrey Sonders)

This topographic reconstruction from satellite photos shows how the Eye is a bullseye bowl in the desert plateau.

Topographic reconstruction of Richat Structure using satellite photos, false coloring to show geology (image from Wikimedia Commons)

In the end, it’s visible because it’s in the Sahara. No vegetation covers it and the wind has blown all the sand away.

(images from Wikimedia Commons and a video by Jeffrey Sonders; click on the captions to see the originals)

The Mole Will Change in 2019

Drawing of hairy-tailed mole (image from Wikimedia Commons)

The definition of a mole will change on 20 May 2019. However, the mammal won’t change, the measure will.

Most of us don’t need to measure the number of atoms, ions, or other tiny entities in a sample of a substance so we’re not aware that the mole (mol) is the unit that does it. Its definition used to be based on 0.012 kilogram of carbon-12 but physical properties can change, so its size could change minutely and throw off precise scientific measurements. This troubled chemical engineers who use the mole extensively.

To fix the problem, the General Conference on Weights and Measures (CGPM) voted at their 16 November 2018 meeting to unlink the mole from its physical definition, redefining it using a mathematical constant. The new definition will be:

One mole of a substance will have exactly 6.02214076×1023 specified “elementary entities” of that substance.

Wikipedia entry for mole (unit)

Three other measuring units had the same problem so the meeting redefined four:

  • Mole: the unit for amount of substance.
  • Ampere: a unit of electric current equal to a flow of one coulomb per second.
  • Kelvin: a temperature scale similar to Celsius but 0 degrees K is absolute zero.
  • Kilogram: the base unit of mass

Perhaps you’ve already heard that the kilogram will change on 20 May 2019. Originally defined as the mass of a litre of water, the kilogram (kg) was redefined in 1799 to be the mass of a block of platinum that’s stored in a vault in Paris. Even the platinum’s mass can change so now the kilogram will be defined by the Planck constant which was defined to be exactly 6.62607015×10-34 kg.m2.s-1. As Wikipedia points out, “This approach effectively defines the kilogram in terms of the second and the metre.”

Notice that the second is raised to minus one, s-1. Is your head spinning? There’s a simpler explanation here in Popular Mechanics.

Meanwhile, why is a hairy-tailed mole (Parascalops breweri) illustrating this article if the message has nothing to do with him? Well, there’s no illustration for the ‘measure’ mole so I’m showing you the ‘mammal’ mole.

(image from Wikimedia Commons; click on the caption to see the original)

How The Mighty Monongahela Lost Its Crown

This used to be the Monongahela River (photo by Kate St. John)

Two million years ago the Monongahela was a mighty river.  Instead of being a short tributary of the Ohio and draining to the Gulf of Mexico, it flowed north to where Lake Erie is today and then to the Atlantic.  This stretch of the Ohio River in Pittsburgh was not the Ohio at all. It was the Monongahela.

Here’s how the mighty Mon River lost its crown and the reason why the Ohio turns south at Beaver, Pennsylvania.

Before the Pleistocene era, the Monongahela River drained 75% of today’s Ohio, Allegheny and Monongahela watersheds as it flowed north from West Virginia to the Lake Erie area (roughly the red arrow path below). 

Back in those days the Ohio River was just a tributary whose northernmost point was in Pennsylvania where it joined the Mon.  The Beaver and Shenango Rivers did not exist as they do today.  Their valleys carried the Monongahela north. 

Approximate flow of historic Monongahela River (derived from river maps at

But then the climate changed. The Great Ice Age began.

Glaciers blocked the Monongahela’s northward flow so the river backed up and formed Lake Monongahela.  The pale dashed lines show the paths of our rivers today bending away from the prehistoric glacier.  

Lake Monongahela (image from Wikimedia Commons)

Eventually Lake Monongahela rose so high that it breached the lowest barrier in the Ohio valley near present day New Martinsville, WV (see orange arrow).

The Ohio started flowing “backwards.” It cut the Ohio River valley deeper, orphaned the northern Monongahela and reversed its flow, creating the Shenango and Beaver Rivers.

All of this was helped by the huge volume of water joining the Mon from the re-formulated Allegheny River watershed.  The Upper and Middle Allegheny river systems used to flow north too, but were also blocked by glaciers. Their proglacial lakes overflowed and joined the Lower Allegheny River flowing into the Ohio watershed.

And so the Monongahela River became a lowly tributary of the Ohio.

Climate change is big stuff.  When it gets cold it changes major rivers.  When it gets hot … Well, we’ll find out.

UPDATE: See the comments!  And here’s a map of the ancient Erigan River drainage from Ohio DNR.

(photo by Kate St. John. Red-arrow map derived from OH & PA river maps at, map of Lake Monongahela from Wikimedia Commons, annotated map of Erigan River via CVNP; click on the captions to see the originals)

Harlequins Warn of Mercury

Male harlequin duck (photo from Wikimedia Commons)

Some birds are canaries in the coal mine, telling us that something’s gone wrong long before we notice it.  Harlequin ducks (Histrionicus histrionicus) are performing that service in Alaska.

A 2017 study by the Biodiversity Research Institute looked for mercury in Alaska’s coastal waters by testing blood samples and molted feathers from harlequin ducks at Kodiak and Unalaska Islands. Blood samples were used because they indicate recently consumed mercury. Molted feathers show mercury when the feathers were formed a year before. 

The study found mercury in harlequins from both locations but those at Unalaska, midway in the Aleutian chain, had eight times more than those at Kodiak, nestled in the Gulf of Alaska. The study then tested the ducks’ main food at Unalaska — blue mussels — and found it there, too.

This is important news for Aleutian residents because they eat lots of seafood.  It also matters to the rest of us since Unalaska’s main port, Dutch Harbor, is the largest fisheries port in the U.S. by volume caught.  

Mercury apparently increases westward in the Aleutian chain. A 2014 study found mercury in fish above the human consumption limit at the western island of Agattu.

Where is the mercury coming from?  In the continental U.S. airborne mercury comes from coal-fired power plants and is regulated and reduced by the EPA.  It can also come from active volcanoes, obviously out of our control.

At this point scientists don’t know where the mercury is coming from, but China’s coal-fired industries are a good bet.  The prevailing wind in the Aleutian Islands originates in Asia more than six months of the year.

Winds over water in the Pacific and Bering Sea, 10 Dec 2018 (screenshot from earth “visualization of global weather conditions, forecast updated every three hours.” )

Unfortunately Alaskans can’t prevent mercury pollution that reaches them from Asia.  Meanwhile the harlequins warn of danger.

(photo of harlequin duck from Wikimedia Commons, screenshot of global winds from earth visualization website; click on the caption links to see the originals)

The Trees Are Still Standing

Camp Fire damage in a Paradise, California, neighborhood, Nov. 17, 2018 (photo by Senior Airman Crystal Housman, California Army National Guard)

In all the smoke-filled photos of the Camp Fire devastation in Paradise, California one thing stands out to me:  The buildings are gone but the trees are still standing.

The town of Paradise, California (population 26,000) was destroyed on 8 November 2018 by the Camp Fire, the deadliest and most destructive fire in California history.  As soon as it ignited at 6:30am, the fire raced westward on 50-70 mph winds. By 8am it reached the Paradise Town Limit six miles away. Seven towns were forced to evacuate but not everyone made it out. As of 26 November, 88 are confirmed dead, 203 are still missing and tens of thousands are left homeless.

But the trees survived.  You can see them in all the photos and videos including these taken on 17 Nov by the California National Guard as they searched the rubble and marked the damage. 

Soldiers from the California Army National Guard’s 649th Engineer Company, Chico, conduct search and debris clearing operations, Nov. 17, 2018, in Paradise, CA (photo by Senior Airman Crystal Housman)

Because the trees are still standing, the damage assessment has to be done by hand. This Washington Post article shows how the satellites can’t see through standing trees. 

So why are the trees OK in this incinerated landscape? I’m sure it has to do with moisture.

U.S. Army Sgt. Rodrigo Estrada of the California Army National Guard’s 649th Engineer Company, Chico, leads a team conducting search and debris clearing operations, Nov. 17, 2018, in Paradise, CA (photo by Senior Airman Crystal Housman)

Living trees contain more moisture than the dry wood in buildings. When blowing embers hit houses, they catch fire immediately. The trees’ moisture resisted. The fire moved on.

This video by Mike West shows how quickly fire consumes dry wood compared to living trees.

The scene is spooky now. Nearly everything is gone but the trees are still standing.

Soldiers from the California Army National Guard’s 649th Engineer Company, Chico, conduct search and debris clearing operations, Nov. 17, 2018, in Paradise, CA (photo by Senior Airman Crystal Housman)

p.s.  Some trees are damaged and will fall sooner or later.  Here’s an NPR story about trees in the fire zone.

p.p.s. See the damage extent on Cal-Fire’s Camp Fire Structure Status map.  See satellite images here in the Washington Post

(photos by Chico California National Guard, YouTube video by Mike West)

Why Don’t Birds Get Electrocuted?

European starlings on wires in Germany (photo from Wikimedia Commons)

In the winter huge flocks of starlings line up on the electric wires.  They even perch on un-insulated wires like those shown above. Why don’t they get electrocuted?

Here’s some helpful background: Electricity is the flow of electrons in a complete circle — called a “circuit” — that moves out from the power source, into our appliances, and all the way back to the power station.  The electrons flow in the path of least resistance.

If a bird steps in and connects the inbound and outbound electron paths it conducts the electricity through its body on a short(er) circuit.  Click here for a video that shows how circuits work.

Birds are safe as long as they don’t short circuit.  The video below explains the electrical reason why birds have to…

  • Touch only one wire. (videomark 0:28 to 0:47)  … and …
  • Not touch a wire and the pole simultaneously. (videomark 0:58 to 1:13)

Birds with long wingspans, like cranes and eagles, can accidentally touch two wires. Smaller birds that mess with the insulators (wire-to-pole connections) can also get electrocuted.

Electric companies prevent bird deaths and worker accidents by placing the wires far apart and increasing the gap between the insulators and the pole (wire-to-pole connections).

No one wants to be a short circuit!

(photo from Wikimedia Commons; click on the caption to see the original)

Fun With Spirals

Nautilus shell cut in half (photo from Wikimedia Commons)

Spirals in nature have a lot in common: Most of them are shaped like this nautilus shell.

Pine cones, flowers and hurricanes follow this same spiral pattern. Did you know they’re described by Fibonacci numbers?

On Throw Back Thursday have fun with spirals in this vintage article: Fibonacci.

Spirals on a pine cone (photo by Kate St. John)
Spirals in a sunflower (photo by Kate St. John)
Satellite image of Hurricane Katia, 31 Aug 2011 (image from NASA, MODIS Rapid Response System on Wikimedia Commons)
Satellite image of Hurricane Katia, 31 Aug 2011 (image from NASA, MODIS Rapid Response System on Wikimedia Commons)

(photo credits: flower and pine cone by Kate St. John, shell and hurricane from Wikimedia Commons; click on the captions to see the originals)

When White Water Is Bad

Waterfall stained white by abandoned mine drainage, Allegheny County along Yough River Trail (photo by Kate St. John)
Waterfall stained white by abandoned mine drainage, Allegheny County along Yough River Trail (photo by Kate St. John)

The Youghiogheny River is famous for whitewater rafting near Ohiopyle but there’s a tributary downstream where white water is bad.

On the GAP Trail north of Buena Vista — near marker 121 — you can hear a rushing waterfall before you see it.  When you reach its location it’s not a pretty sight. The waterfall stains everything white.

Early this month I looked at the water and its outflow in the Youghiogheny River and discovered that the water is clear and colorless, though it leaves a white residue on everything it touches.

Here are some closer looks.

Closeup of dripping white residue, Allegheny County along Yough River Trail (photo by Kate St. John)
Closeup of dripping white residue in a tributary of the Youghigheny River, Allegheny County (photo by Kate St. John)
Rocks stained white by abandoned mine drainage, at Yough River Trail (photo by Kate St. John)
Rocks stained white by abandoned mine drainage, at Yough River Trail (photo by Kate St. John)

The water is clear because it’s acidic. The residue is from abandoned mine drainage (AMD), a problem that pollutes more than 2,500 miles of Pennsylvania rivers and streams.

Most AMD in western Pennsylvania is orange like this outfall into Chartiers Creek at Wingfield Pines Conservation Area. The rust color comes from dissolved iron.

Orange ferrihydrite water pollution from abandoned mine drainage, Chartiers Creek, April 2016 (photo by Kate St. John)
Ferrihydrite: orange water pollution from abandoned mine drainage, Chartiers Creek, April 2016 (photo by Kate St. John)

The white waterfall is caused by dissolved aluminum sulfate from an old coal mine in the hill above the waterfall. 

Aluminum sulfate crystals (photo from Wikimedia Commons)

As water from the abandoned mine travels downhill it blends with clean water that raises the pH (i.e. lowers the acidity). At some point the diluted mine water isn’t acidic enough to dissolve aluminum sulfate so the aluminum precipitates out as white residue.

This color is somewhat unusual but there are other white streams in Allegheny County including Milk Run in North Fayette Township along Mahoney Road.  This year the Allegheny County Conservation District is reclaiming Milk Run at the cost of nearly a million dollars.

I can’t imagine the price tag for fixing the White Waterfall.

(photo credits: waterfall by Kate St. John. Aluminum sulfate crystals from Wikimedia Commons; click on the caption to see the original)

Forbidden Food

Amaranth in bloom (photo from Wikimedia Commons)
Amaranth in bloom (photo from Wikimedia Commons)

On a recent trip past Exit 163 on Interstate 70, I was intrigued by the name Amaranth.    Two towns in Canada, one in Portugal, and one in Fulton County, Pennsylvania have that name.  What does it mean?

“Amaranth” is a flower that never fades, a reddish dye, or — primarily — a grain-like food native to the tropical Americas.  It was a staple of the Central American diet until the Spanish Conquistadors outlawed it when they conquered the Aztecs in 1521.

Back then the grain played a supporting role in religious human sacrifice. Eerily similar to the Eucharist in which Jesus told his disciplines to consume bread and wine symbolizing his body and blood, the Aztecs performed human sacrifices and ate cakes of amaranth mixed with real human blood.

The Spanish abolished all of that.  The penalty for growing amaranth was death. But the plant survived. It became a weed.

One of the weediest in the Amaranthus genus is red-rooted pigweed or green amaranth (Amaranthus retroflexus), a 1-6 foot annual whose flowers bloom in bristly spikes in August (photo at top).  This patch is in a German asparagus field.

Amaranth found as a weed in an asparagus field (photo from Wikimedia Commons)
Amaranth in a field near Reilingen (photo from Wikimedia Commons)

I think pigweed is ugly. However you can eat it, though it probably doesn’t taste as good as the cultivated species

Each tiny flower produces a seed topped by a tiny cap.  Pop the seed and eat the grain or grind it into flour for bread and cereal.

Fruit with seed; amaranth grain (photos from Wikimedia Commons: fruit, grain)
Fruit with seed; amaranth grain (photos from Wikimedia Commons: fruit, grain)

You can eat the leaves, too, but they contain a small amount of oxalic acid so they must be boiled and drained. In India, the leaves are the main ingredient in Kerala-style thoran.

Today many people plant amaranth varieties for their red flowers, the color of amaranth dye.

Red amaranth flowers (photo from Wikimedia Commons)
Red amaranth flowers (photo from Wikimedia Commons)

Most of us don’t realize it was a forbidden food.

Read more about amaranth as food in the New York Times, Grain of the Future, October 1984 and Public Radio International, Return of an Ancient Grain, July 2013.

p.s. Did you know that quinoa is in the amaranth family?

(photos from Wikimedia Commons; click on the captions to see the originals)

Sinks And Traps

Sink hole in Wales (photo from Wikimedia Commons)
Sink hole in a limestone region of Wales (photo from Wikimedia Commons)

Today’s blog about sinks and traps is not about plumbing …

bathroom sink (photo from Wikimedia Commons)

Last week Michelle Kienholz noticed that the mockingbird family near her office was under predation pressure again. In June half the family was eaten by a red-tailed hawk. On Friday two flightless young were frightened to the ground.  Michelle put them in a thick bush and hoped for the best.  I thought to myself, “That place is a biological sink for mockingbirds.”

Like a sink hole, shown at top, a biological sink is where a species breeds but the habitat works against them so they always fail to produce enough young to replace themselves. The population sinks at that site.

A sink can be offset by a high quality habitat called a biological source where the population more than replaces itself.  If the sources equal the sinks the population remains stable.  If the sources outweigh the sinks the population grows.  This balancing act is called source-sink dynamics.

Sometimes a sink is so attractive to breeders that they’re drawn to it in large numbers even though they always fail.  These ecological traps cause localized population crashes.

A good example of an ecological trap is the effect that outdoor lights have on mayflies.

Mayflies lay their eggs on water, often at night.  To find water in the dark they look for the polarized light reflection of the moon on water. Unfortunately, our outdoor electric lights are like thousands of moons that reflect off artificial polarizing surfaces — asphalt, cars, windows, etc.  The mayflies mistake these false surfaces for huge bodies of water and land there to lay eggs.  The locations are both sinks and traps.  All the mayfly eggs are wasted.

Mayflies on a car at Catawba Island, Ohio (photo by Rona Proudfoot on Flickr, Creative Commons license)
Mayflies on a car at Catawba Island, Ohio (photo by Rona Proudfoot on Flickr, Creative Commons license)

The number of mayflies that fall for these traps can be astonishing.  In June 2015 in Wrightsville, PA on the Susquehanna River, there were so many mayflies on the Route 462 bridge that the surface became slippery with dead mayfly bodies.  They had to close the bridge.

I suspect that if they’d turned off the streetlights while the bridge was closed, the trap would have disappeared, the mayflies would have gone elsewhere, and there would have been less to clean up.

(credits: video from WGAL-TV via YouTube.  photo of car with mayflies by Rona Proudfoot on Flickr Creative Commons license. All other photos from Wikimedia Commons. Click on the images to see the originals)