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David Webster

@davidjwebster.bsky.social

Geologist, Islay geology guide book author, Fossil Grove trustee, whisky lover. Secretary Geological Society of Glasgow.

18 Posts196 Follower163 Folgt
Oliver Strimpel@geologybites.bsky.social · last yr.

🧪⚒️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.
Oliver Strimpel@geologybites.bsky.social · last yr.

🧪⚒️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 CalTechPlot 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
Oliver Strimpel@geologybites.bsky.social · last yr.

🧪⚒️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.
The Geological Society of Glasgow@geolsocglasgow.bsky.social · last yr.

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

The Geological Society of Glasgow@geolsocglasgow.bsky.social · 2y ago

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

David Webster@davidjwebster.bsky.social · 3y ago

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!

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