Sunday, March 3, 2024

Giant Beavers!

Did you know there were once giant beavers roaming the Hudson Valley region?

Bear-sized giant beavers (Castoroides ohioensis) lived during the Pleistocene Epoch (the time of the most recent ice age) and grew to over 7 feet in length with a weight of over 200 pounds. As their scientific name implies, they were first discovered in Ohio (1837) but extended from the upper Midwest and Canada over to the east coast (another species - Castoroides dilophidus - existed in the southeastern U.S.).

Giant beavers did exist in the Hudson Valley. One, for example, was discovered (along with caribou and flat-headed peccary fossils) at the Dutchess Quarry Cave site near Middletown in Orange County (near where a lot of mastodons have also been discovered). At this site, the beaver radiocarbon dated to 11,670 +/-70 years before present.

Castoroides ohioensis skeleton in the Field Museum, Chicago

Here's an artist's conception by the famous early 20th century illustrator Charles R. Knight.


The giant beaver differed from modern beavers in that they probably had rounded tails and not the flattened ones seen today and also in their teeth. Their teeth were much longer (up to 6 inches) and were ridged unlike the smooth teeth of modern beavers. These ridges would have strengthened their teeth and their jaw structure suggests that they would have had a strong biting force. It's hard to say if they constructed dams and lodges as beavers do today and stable isotope evidence from their bones indicates a mostly aquatic plant diet. Their large teeth were likely better adapted to digging in pond muck than in cutting trees.

Giant beavers first appear in the fossil record near the start of the Pleistocene ice age almost 2 million years ago and died out around 11,000 years ago as the North American climate was warming and glaciers had retreated north. The end of their time also overlapped with the migration of paleo-Indians into eastern North America. Did they die off due to climate change or did humans kill them off? This is the perennial question of all the Pleistocene megafauna which vanished around the same time.

While there is no direct evidence these early Native Americans hunted giant beavers (although it seems unlikely they would not have utilized all food source animals) some of the tribes have stories and legends that seem to be about them (it's amazing to think about oral traditions lasting thousands of years). They feature in an eastern Cree creation story and in tales by the Chippewa, Seneca, and other tribes (see, for example, https://www.jstor.org/stable/481746).

The Hudson Valley was a very different place just a few thousand years ago!

Monday, February 26, 2024

Learning from the past

There was a recent paper in Science Advances that’s gotten a lot of press lately. It discusses the possible collapse of the Atlantic meridional overturning circulation (AMOC) due to warming from climate change. This is not a new idea, here’s a July 2023 paper in Nature Communications saying the same thing (and forecasting a timeline between 2025 and the end of the century).

Basically, colder and more saline ocean water is more dense than warmer and less saline ocean water and these density differences lead to the development of areas of sinking water which drive deep currents (called thermohaline currents). These thermohaline currents are effectively mixing oceanic waters around the globe and hugely important in global climate.

In the AMOC, the Gulf Stream and North Atlantic Current bring warmer waters from the equatorial regions northward. At higher latitudes, this now colder water sinks down to drive deep thermohaline currents circulating water back south. If global temperatures continue to warm, the melting Greenland ice cap will dump enough freshwater into the North Atlantic to potentially disrupt the AMOC. This will have profound climatic implications for all of us.

Geologists, who have a longer view of things, know that the AMOC hasn’t always existed and there have been times during the last ice age when it has repeatedly collapsed and restarted. One of those times it collapsed may be tied to events right here in the Hudson Valley.

Some papers have suggested that a time known as the Intra-Allerød cold period that began around 13,360 years before present (B.P.) was due to temporary collapse of the AMOC. As the mighty continental glaciers melted back into Canada around 13,400 B.P., large amounts of meltwater were flowing south down through the Hudson Valley. Glacial moraines (ridges of glacial sediment called till) formed dams down by the Hudson Highlands formed a large freshwater lake called Lake Albany. Lake Albany was over 150 miles long and over 200 feet deep in places.

 

Also dammed up was what’s now Lake Ontario. It was much larger at this time and called Lake Iroquois (misspelled in the diagram below). Eventually Lake Iroquois broke through the dam and massive amounts of meltwater raced down the Hudson Valley and into the Atlantic Ocean (the whole story is a bit more complicated but you get the picture). There is evidence for this event both in the sediments of the Hudson Valley as well as features on the continental shelf seafloor out from the mouth of the Hudson River.

 The hypothesis is that this massive influx of freshwater disrupted the AMOC and led to a cooling period known in paleoclimatology as the Intra-Allerød cold period. It’s not fully accepted due to difficulties in getting exact dates and correlations for events occurring thousands of year ago, but certainly an intriguing hypothesis and perhaps indicative of events going on in the present day with the Greenland ice cap.

 It also shows how the study of geology can help us understand events occurring in the modern day.

Sunday, February 18, 2024

New Plates

 Just a short post today...

The Hudson Valley Geologist's wife bought me new customized license plates for Valentine's Day. I love them!



Sunday, February 11, 2024

Obsidian

If you frequent certain areas of social media, or visit new age mineral shops, you may have seen stuff touted as obsidian that is nothing but colored glass.

Real obsidian is volcanic glass. It's formed from volcanic eruptions when lava (molten rock) cools so quickly minerals don't have time to nucleate and grow. Most obsidian is black and glassy with distinctive conchoidal fracture.


Conchoidal fracture can be seen in the sample above and is the curved, shell-like way obsidian (and other glass) breaks leaving sharp edges. Native people around the world took advantage of this fracture pattern to use obsidian to make knives and spear tips.

Some obsidian has inclusions of a white mineral called cristobalite (a form of quartz) leading it to be called snowflake obsidian which is very pretty when tumbled or carved.


Mahogany obsidian has a brown coloration from some trapped iron oxide in the rock.


There are also some rare varieties of obsidian (sheen, rainbow, or fire obsidian) that show a metallic sheen or colorful iridescence. This is usually from microscopic gas bubbles or different mineral inclusions that reflect various wavelengths of light.


When visiting metaphysical shops that sell crystals, as I'm wont to do out of curiosity (I usually don't buy from them because I can go to rock and mineral shows and buy genuine samples at a fraction of the price), I have started seeing a lot of colored glass being sold as "obsidian". Here are some examples from Etsy.


While marketed as obsidian, and sometimes priced at hundreds of dollars, these are really just hunks of colored glass. They're usually formed as a by-product of steel manufacturing and found in industrial dumps. One variety that I know of is artificially manufactured from Mt St Helens ash (Helenite) and sold as natural. It about as natural as your kitchen window.

These are often marketed as Andara crystal, blue, green, or red obsidian, Gaia obsidian, Aqua Lemuria, and other made-up names with sometimes outrageous magical claims associated. Break a green beer bottle if you want some green glass - it will have about the same healing energy as these "crystals" and you can drink the beer beforehand.