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davidjwebster.bsky.social
David Webster
@davidjwebster.bsky.social
190 followers 160 following 17 posts
Geologist, Islay geology guide book author, Fossil Grove trustee, whisky lover. Secretary Geological Society of Glasgow.
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davidjwebster.bsky.social
Come to the Fossil Grove this Sunday (15th) - anytime 12-4. Come and hear about what's going on with the renovation programme. Tours of the quarry area. Children's activities. Displays and fossils. (Note: The building itself is closed).
www.fossilgroveglasgow.org
June 11, 2025 at 9:57 PM
davidjwebster.bsky.social
Good turn out today for a geology walk on the Rhinns of Islay. 1.8 Ga Metagabbro and syenitic gneiss. Triassic faulting, Paleocene dykes and late glacial raised beaches... www.islaygeology.org
June 1, 2025 at 8:25 PM
Reposted by David Webster
🧪⚒️I just posted an episode on megafloods with Vic Baker, a pioneer in the field. Megafloods are cataclysmic events that devastate the landscape. The Mediterranean Basin was filled by two successive megafloods. And a Black Sea megaflood might be the basis for the Biblical account of Noah's flood.
Until about 425,000 years ago, Great Britain was joined to Europe by a narrow isthmus along the Weald-Artois anticline, a fold consisting of the Cretaceous chalk that is today cut at the cliffs of Dover in England and the Cap Blanc Nez near Calais in France. As Baker discusses in the podcast, a large glacial lake formed south of an ice cap spanning northern Britain and Scandinavia. This lake eventually breached the isthmus, resulting in a megaflood that eroded what is now the seafloor below the English Channel into a steep-sided inner channel and plunge pools. Map view (right) and topography (below right) of the Kasei Vallis megaflood channel. Kasei Vallis is the largest of the Martian outflow channels, about 3,000 km long and up to as much as 400 km wide in the areas shown at right. Rock basins eroded into Columbia River Basalt at Lenore canyon, Lower Grand Coulee in the Channeled Scabland of Eastern Washington. Note the roads for scale. Giant current ripples at West Bar, near Trinidad, Washington.
April 13, 2025 at 2:54 PM
Reposted by David Webster
🧪⚒️New episode - Lindy Elkins-Tanton on the origin of Earth's water. Only about 0.02% of the Earth is water, but even that's been a puzzle as Earth formed within the snow line where no liquid water would have been present. Isotopic analysis provides the clues to resolve this apparent paradox.
Microwave image of a protoplanetary disk surrounding the young star HL Tauri. The disk includes gaps possibly cleared by amalgamation onto newly-forming planets. This image was taken by the Atacama Large Millimeter/submillimeter Array interferometer, consisting of 66 radio telescopes in the Atacama Desert of northern Chile. ALMA (ESO/NAOJ/NRAO) Artist’s impression of a region of a giant molecular cloud that is collapsing to form a protoplanetary disk of gas and dust. A star forms at the center of the disk, and planets form out of the disk. NASA/JPL CalTech Plot of various solar system materials. The plot shows that the isotope ratios of hydrogen (D/H) and nitrogen (15N/14N) on Earth are very different from those of comets but quite similar to those of a certain class of meteorites called enstatite chondrites. If comets had delivered Earth’s water, they would have changed its nitrogen isotopic ratios as well as its hydrogen isotopic ratios. Isotopic fingerprinting strongly suggests that Earth’s water has come from the enstatite chondrites. Marty, B. (2012), Earth and Planetary Science Letters 313, 56
March 27, 2025 at 7:46 PM
Reposted by David Webster
geologyglasgow.bsky.social
Change to lecture programme tonight. David Webster will talk about the geology of the island of Colonsay. Palaeoproterozoic basement, the overlying Colonsay Group and spectacular igneous intrusions plus the earliest radiometric dating and 'granitisation'.
geologyglasgow.org.uk/event/colons...
The Geology of Colonsay | Geological Society of Glasgow
by David Webster
geologyglasgow.org.uk
March 13, 2025 at 7:07 AM
Reposted by David Webster
🧪⚒️I just posted an episode about using the late Paleozoic ice age as an analog to climate conditions today. It was similar in that there was low but rising CO2 and continental ice sheets. Her models suggest possible major ocean anoxia and dramatically increased runoff as CO2 climbs.
Results of the Earth-System Model for atmospheric CO2 levels of 280 parts per million (ppm) and 560 ppm for the late Paleozoic. Top row: sea ice forms at 280 ppm but not at 560 ppm. Bottom row: at 280 ppm, the late-winter mixed layer of the ocean is moderately deep but becomes much shallower at 560 ppm. Simulations show the response of seawater density & temperature by depth for a doubling of CO2. Sea surface salinity (i.e., density) increases at low CO2 due to sea ice formation, which excludes salt, thus creating briny water, whereas at high CO2 less sea ice formation leads to decreased density overall. Plots of oceanic depth vs. latitude of the time since a water mass has been in contact with the surface. Younger ages in shades of purple indicate well-ventilated waters, whereas older ages in orange and yellow indicate poorly ventilated waters that typically correlate with low dissolved O2 in the deep ocean. Together with the sea ice and mixing depth results, this suggests the onset of widespread seafloor anoxia during the CO2-forced warming despite being under deep glacial conditions.
March 8, 2025 at 6:56 PM
Reposted by David Webster
geologyglasgow.bsky.social
Next Lecture at the Geological Society of Glasgow. Dr Simon Cuthbert on eclogites in NW Scotland. Thursday 13th March at 7pm Boyd Orr Building, Room 407 - All welcome.
geologyglasgow.org.uk/event/eclogi...
Eclogite Shangri-La: Vestiges of the Grenville orogen in the northwest Scottish Highlands (and some heroes of Scottish geology) | Geological Society of Glasgow
Dr. Simon Cuthbert, Retiring Presidential Address
geologyglasgow.org.uk
March 6, 2025 at 7:59 AM
Reposted by David Webster
geologyglasgow.bsky.social
Our next lecture is on Thursday 6th February at 7pm in Room 407 of the Boyd Orr Building, University of Glasgow. Dr Alex Dunhill will talk on "Species loss, community collapse and ecosystem recovery during times of mass extinction" geologyglasgow.org.uk/.../species-...
All welcome.
Species loss, community collapse and ecosystem recovery during times of mass extinction | Geological Society of Glasgow
Dr Alex Dunhill, University of Leeds
geologyglasgow.org.uk
January 31, 2025 at 8:03 PM
davidjwebster.bsky.social
@bobgooday.bsky.social bob, any idea about this rock? i was sent a photo and would like to get back to the sender. its from lamlash on arran so immediately thought of you! i think some form of explosion breccia with a carbonate infill? thanks
December 28, 2024 at 9:52 PM
Reposted by David Webster
geologyglasgow.bsky.social
Here is a link to a recording of last Thursday's lecture given by Paige dePolo on pantodonts (weird early mammals) from New Mexico. Its well worth a view, she was very entertaining and knowledgeable! youtu.be/RWamAw6uo10
The taphonomy of a pantodont-rich assemblage from the San Juan Basin, New Mexico, USA
YouTube video by Geological Society of Glasgow
youtu.be
December 14, 2024 at 6:37 PM
Reposted by David Webster
geologyglasgow.bsky.social
Next Lecture at the Geological Society of Glasgow. Thursday 12th December at 7pm. Room 407 Boyd Orr Building. ALL WELCOME!
Dr. Paige dePolo, Liverpool John Moores University
“The taphonomy of a pantodont-rich assemblage from the San Juan Basin, New Mexico, USA”
geologyglasgow.org.uk/event/the-ta...
November 30, 2024 at 11:57 AM
davidjwebster.bsky.social
Nice anticline in metagreywackes at Saligo Bay, Islay. The area is known as The Arches' after the fold. Colonsay Group (earliest Dalradian, c. 800 Ma) #fridayfold
November 22, 2024 at 7:34 PM
davidjwebster.bsky.social
Good to see a bit of Scottish rock from Islay in your collection! Look out for new Geol Soc memoir on the Port Askaig Fm next year
callanbentley.bsky.social Callan Bentley @callanbentley.bsky.social · Nov 20
Sample set for my Snowball Earth lab exercise in Historical Geology. ⚒️
Eleven trays on a tabletop, each holding one or more rock samples. Visible labels include Gaskets, Kinston Peak, Fauquier, Mechums River, Port Askaig, Gowganda, and Konnarock.
November 20, 2024 at 11:49 AM
Reposted by David Webster
geologyglasgow.bsky.social
Geological Society of Glasgow's YouTube channel for previous lecture recordings etc.
www.youtube.com/channel/UCfN...
Geological Society of Glasgow
www.youtube.com
November 19, 2024 at 2:20 PM
Reposted by David Webster
geologyglasgow.bsky.social
A link to the November 2024 Lecture by Heather Stewart on "The abyss gazes also into you: exploring the deepest oceans"
youtu.be/-6b9bi-AehM
The abyss gazes also into you: exploring the deepest oceans
YouTube video by Geological Society of Glasgow
youtu.be
November 19, 2024 at 2:07 PM
davidjwebster.bsky.social
New paper helps tie down the start, age and duration of the Cryogenian 'Sturtian' glaciation. Zircons in the Port Askaig Formation from the Garvellach Islands show YSG younging-upwards and help the case for a 'Golden Spike' there. For now we make do with a golden carrot! doi.org/10.1144/jgs2...
August 23, 2024 at 10:11 AM
davidjwebster.bsky.social
Geological Society of Glasgow Monthly Lecture - Thursday 14th March 2024
Dr. Murray Reid,
“What lies beneath: the geology of Strathkelvin”
Boyd Orr Building 7.00 pm
March 5, 2024 at 8:05 PM
davidjwebster.bsky.social
Email sec@gsocg.org for zoom link
davidjwebster.bsky.social David Webster @davidjwebster.bsky.social · Feb 2
Geological society of glasgow - Next lecture Biogeochemical cycling of essential elements within Mars analogue sites by Toni Galloway (St Andrews). Thursday 8th Feb 19:00 by zoom.
us02web.zoom.us/j/87137408991?…
February 2, 2024 at 8:04 PM
davidjwebster.bsky.social
Geological society of glasgow - Next lecture Biogeochemical cycling of essential elements within Mars analogue sites by Toni Galloway (St Andrews). Thursday 8th Feb 19:00 by zoom.
us02web.zoom.us/j/87137408991?…
February 2, 2024 at 8:02 PM
davidjwebster.bsky.social
TV camera at the fossil grove today. Much excitement! Glasgow City Council has agreed to fund £450,000 worth of repairs to the building to help conserve the fossils for future generations to enjoy.. a big result for geoconservation!
November 30, 2023 at 1:45 PM
davidjwebster.bsky.social
I've listened to every episode, some many times. They get me up and down mountains. Essential listening for any earth scientist. Thanks oliver.
melaniefinch.bsky.social Melanie Finch @melaniefinch.bsky.social · Nov 26
I love this podcast, I’ve listened to every episode 🤩 Thanks for making it. I find it useful for my teaching too.
November 27, 2023 at 9:05 AM
davidjwebster.bsky.social
The 'billion-year gap' at Kilchiaran Bay, Islay. 1.8 Ga gneiss on right, 800 Ma meta-arkoses on left. Sinistral shear sense.
November 25, 2023 at 9:33 PM