Allen J. Dennis
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ad3nnis.bsky.social
Allen J. Dennis
@ad3nnis.bsky.social
450 followers 410 following 210 posts
Geologist, Professor
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Gift 🎁 article
Earth Is Being Cooked at a Quickening Pace
www.nytimes.com/2025/06/26/c...
by
@sachimulkey.bsky.social @rjnskl.bsky.social
& Claire Brown
June 29, 2025 at 10:09 PM
ad3nnis.bsky.social
Driving south on 75 towards Atlanta, on the phone with @drbruceherbert.bsky.social I missed the north Georgia bolide, Th 6/26/2025.

Ivan Ehlers, The New Yorker, April 17, 2025
June 28, 2025 at 7:30 PM
ad3nnis.bsky.social
The GENIUS Act. Privatize the profits, socialize the risks for stablecoin speculators
May 22, 2025 at 10:49 AM
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This is from the old bird site. I captured it before I left. How many times it has applied in the past 5-6 years. Thank you for writing it, Dr. Freeman. I have shared it with many friends and colleagues. I have had some great mentors. Every day I give thanks for them.
May 4, 2025 at 11:37 PM
ad3nnis.bsky.social
From Reuters article
Mandalay, Myanmar M7.7 Mar 28, 2025 quake
April 29, 2025 at 9:58 AM
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There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy.

Hamlet, Act I, Sc 5.

Happy Birthday Wills.

Understood people and had a way with words.

Celebrate responsibly!
April 23, 2025 at 2:37 PM
ad3nnis.bsky.social
On the left is Darwin's first written conception of the "tree of life," on the right Carl Woese's tree that is the basis for all modern trees. I have often wondered whether Woese drew his to look like Darwin's concept.
April 23, 2025 at 1:14 PM
ad3nnis.bsky.social
Let's try and do this this week.
Gift article 🎁

A Parade of Planets Is Marching Through the Night Sky
www.nytimes.com/2025/02/24/s...
Schematic of the night sky last week in Feb 2025 showing the view looking West at sunset. Going up from the horizon: Saturn, Mercury, Neptune (may require binocs or telescope), Venus, Uranus (may also require binocs) Jupiter (to the right of Orion), and Mars.
February 25, 2025 at 2:03 AM
ad3nnis.bsky.social
Today is Charles Lyell's death date (1875), 150 years ago. Lyell was the great popularizer of Uniformitarianism: if we know the circumstances under which particular rocks form, when we see those rocks in the geologic record, we can interpret the processes active in the past.
Charles Lyell's tombstone in Westminster Cathedral, a slab of fossiliferous Carboniferous limestone, Wicksworth, Derbyshire, inlaid in brass on the stone is following: CHARLES LYELL BARONET F.R.S. AUTHOR OF THE PRINCIPLES OF GEOLOGY BORN AT KINNORDY IN FORFARSH NOVEMBER 14, 1797 DIED IN LONDON FEBRUARY 22,1875 THROUGHOUT A LONG AND LABORIOUS LIFE HE SOUGHT THE MEANS OF DECIPHERING THE FRAGMENTARY RECORDS OF THE EARTH'S HISTORY IN THE PATIENT INVESTIGATION OF THE PRESENT ORDER OF NATURE, ENLARGING THE BOUNDARIES OF KNOWLEDGE, AND LEAVING ON SCIENTIFIC THOUGHT AN ENDURING INFLUENCE O LORD HOW GREAT ARE THY WORKS, AND THY THOUGHTS ARE VERY DEEP. PSALM XCII. 5.
February 23, 2025 at 2:09 AM
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Today is one of my favorite days: the shared birthday of Darwin and Lincoln, February 12, 1809. In 2018 we visited Darwin's home Down House, and a highlight was walking the Sandwalk where he walked daily considering the problem he was working on.
Photo © Allen Dennis, 2018 View down Charles Darwin's Sandwalk, Down House. On a sunny day, tall trees on the right completely shade a brown gravel path. To the left a (barbed?) wire fence with wooden fence posts separates the path from a sunlit hayfield. About 50m away, the shade from the trees gives out, and a small sunlit view looks like the light at the end of a tunnel. The row of trees on the side of the photo is called a shaw, and was planted at D's instruction. The pebbles on the sandwalk are of a local chert. As Darwin walked up and down this path, he would make a pile of pebbles to mark the number of laps he had walked. His children would add/take away from the pile when he headed the other direction. Photo © Allen Dennis, 2018 View down Charles Darwin's Sandwalk, Down House. On a sunny day, tall trees on the left shade a tan gravel path. To the right hedges separate the path from a sunlit tallgrass field. At the end of the path, about 40m away, a small wooden shed open on one side contains a bench. The row of trees on the L side of the photo is called a shaw, and was planted at D's instruction. Barely visible at the end of the Sandwalk is a small shed with a small bench, almost like a shelter at a bus-stop; this is a reproduction of a structure D had built. The pebbles on the sandwalk are of a local chert. As Darwin walked up and down this path, he would make a pile of pebbles to mark the number of laps he had walked. His children would add/take away from the pile when he headed the other direction.
February 12, 2025 at 10:52 AM
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I missed posting yday on Intl Day of Women & Girls in Science. The word Scientist was coined in 1834 to describe Mary Somerville by William Whewell reviewing her book On the Connexion of the Physical Sciences.

Her portrait on the 2017 Scottish 10£ note

#internationaldayofwomenandgirlsinscience
2017 Scottish polymer 10£ note with portrait of mathematician, polymath and author, Mary Somerville. Includes quote from her book On the Connexion of the Physical Sciences: “Anyone who has observed the reflection of the waves from a wall on the side of a river after the passage of a steam-boat, will have a perfect idea of the reflection of sound and light”.
February 12, 2025 at 10:26 AM
ad3nnis.bsky.social
Testing AMOC collapse models with a millennial-scale composite growth ring-oxygen isotope-carbon isotope chronology compiled from Artica islandica clam shells collected offshore Iceland.
Outstanding reporting by @sarahkaplan48.bsky.social

www.washingtonpost.com/climate-envi...
The global ocean circulation system, shown in part here, transports water, heat and nutrients between the equator and the poles. The Atlantic Meridional Overturning Circulation is part of this complex system of ocean currents. (NOAA)
January 6, 2025 at 1:05 AM
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Best News & Views-style overview of implications of Speidel et al's Twigstats-based European migration study from Francis Crick Institute. Beautifully illustrated.
www.crick.ac.uk/news-and-rep...
Image inspired by the serpentine carvings found on Viking Age runestones, featuring the runes for DNA bases A, G and C. Credit: Oliver Uberti.
January 4, 2025 at 9:38 AM
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Casting a light on the Triassic.
An unusual essay from the Economist. I didn't have a problem entering my email and getting a one-time # code for access.
Photo: Cotylosaur jaws from core DRB-10 recovered from the Tr Dunbarton basin, Savannah River Site, SC. ≈5cm.
www.economist.com/christmas-sp...
Cotylosaur jaw/ teeth recovered from DRB-10 core by Tim Chowns (WGC&SU) from Triassic core recovered from the Dunbarton basin, Savannah River Site, SC. This view is about the length of two joints on my pinky. Cotylosaurs went extinct at the mass extinction in late Triassic time, about the time of the eruption of the Central Atlantic Magmatic Province (CAMP), and the opening of the present day Atlantic. This extinction was the advent of the "true" dinosaurs.
December 22, 2024 at 1:40 PM
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How many epiphanies have we had in the past 7 years? Near the top of the list for me were reading the Human Planet by @simonlewis.bsky.social & @profmarkmaslin.bsky.social w a chaser of @georgemonbiot.bsky.social essay linked here.
#Anthropocene
www.monbiot.com/2021/10/11/f...
December 11, 2024 at 11:53 PM
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December 2, 2024 at 5:04 AM
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Figure 10.1 Dinosaurs: A concise natural history, Fastovsky & Weishampel, Cambridge Univ Press, p. 215.

Skeleton of pigeon, a) feather structure; b) carpometacarpus; c) tarsometatarsus; d) synsacrum w pygostyle; e) hollow bone w pneumatic foramina; (f) sternum w keel; (g) furcula (wishbone)
December 1, 2024 at 6:47 PM
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Tastes like eumaniraptoran theropod.

My students are fascinated by comparative anatomy of theropod dinosaurs (like T rex, and Deinonychus) & ancestry of birds, the sole remaining theropods.

Figure 10.5 Dinosaurs: A concise natural history, Fastovsky & Weishampel, Cambridge Univ Press, p. 210-221.
December 1, 2024 at 6:39 PM
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This time of year I look forward to sketching alpine glacial retreat in introductory labs; students use the drawing suppl by text to identify alpine glacial features on the Chief Mtn, MT topo. I also show students how to adjust contrast, black point, saturation to make my chalk drawings pop.
Four alpine glacial valleys on a single mountain show progressive glacial retreat, read from right to left in a chalkboard drawing. Alpine glacial features are labeled on the photo. Colors have been adjusted in the photo to make the drawing "pop."
November 29, 2024 at 11:53 AM
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Sand volcanoes formed during the Charleston Earthquake Aug 31, 1886. South of Summerville. Clarence Dutton prepared the USGS report on the earthquake. Novelist Wallace Stegner wrote his Ph.D. thesis as a biography of Dutton.
September 1, 2024 at 6:55 AM
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Charleston (SC) earthquake anniversary (1886).
This train derailment occurred just a few km from my home, 160 km from the epicenter.
September 1, 2024 at 6:53 AM
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Cicadas: Dual emergence of Brood XIII (blue 17 year cycle) and Brood XIX (red, 13 year cycle) begins near the end of April, last seen in 1803.
by @aimee-ortiz.bsky.social
www.nytimes.com/2024/01/19/s...
January 21, 2024 at 8:51 AM