Callan Bentley A new week, a new nonfiction geology book by John Dvorak! This one is a biography of Thomas Jaggar, who founded the Hawaiian Volcano Observatory. It was a really interesting portrait of a man driven to spend time with erupting mountains. The book begins with the eruption of Mt. Pelee in Martinique, a harrowing pyroclastic … Read more
So many books have been written about dinosaurs, but this one looks at a deeper history of another important group: our own. Beasts Before Us is “the untold story of mammal origins and evolution.” The Cenozoic is often dubbed “the age of mammals,” but the story of our hairy, milk-guzzling brethren goes much deeper into … Read more
Reader Nancy Weidman (who supplied the Wind River boudinaged basaltic dike images from earlier in the week) sent me this interesting note: Your ichnoanalogue post reminds me of the insect or pillbug tracks I found in Mt. St. Helens ash deposited in Missoula, Montana. At least some of the tracks, if I recall correctly, ended … Read more
Callan documents a geological stroll along the coast of Esterillos Oeste, in central southern Costa Rica, investigating the sequence of sediment in the Punta Judas Formation (Mid-Miocene) exposed there. Fossils, sedimentary structure, diagenetic features, structural deformation, and modern weathering all make prominent appearances.
Got these photos from a reader, showing outcrops in the northern Wind River range (ESE of Island Lake). The question, inevitably, is are these MMEs (microgranular mafic enclaves) or xenoliths? They’re fine grained and mafic… but some lithologies of xenolith could be too! This next set shows what appear to be a bunch of blocks … Read more
Two weeks ago was the annual Virginia Geological Field Conference, which was centered this year on the Goochland Terrane, an interesting block of crust in the Piedmont which shows some similarities to the Blue Ridge geologic province, but also shows some differences that suggest it’s not just a mini-Blue-Ridge. One of the best exposures was … Read more
Inspired by How The Mountains Grew, I ordered the rest of John Dvorak’s oeuvre recently. I read the first over Thanksgiving break – a great nonfiction look at eclipses. The basics of lunar and solar eclipses are dispensed with early on, and Dvorak then spends his time on understanding of eclipses in antiquity, the gradual … Read more
Another glimpse of sand on the beach at Esterillos Oeste, Costa Rica… This time, I offer you a trace of an organism moving through the wet sediment: Note the two parallel lines of tracks laid down by little feet, and the central groove that overprints them. It reminded me very much of this similar arrangement, … Read more
Callan offers reviews of a suite of good reads – some old and some new, some geology and some general science, and some social justice/history.
