I collected only a single rock on my summer travels in France and Italy. (Those of you who know me will realize how extraordinary this low number is!) It’s a flow-banded rhyolite from Vulcano, in the Aeolian Islands north of Sicily a few weeks ago. It contains porphyritic vesicular basalt xenoliths. I featured a similar … Read more
Can soft sediment deformation “loading structures” (ball & pillow) occur when the two strata are identical in composition? Grok on these field photos and chime in with your best hypothesis.
I’ve been busy making 3D models lately. Here are three ones united by a theme of being sand that was deposited relative to mud. In one case we have scouring to make flutes, in another case we have have localized sagging to make “ball & pillow” structures, and in the third case we have an … Read more
Deep in the Archean, things suddenly got violent in the deep water of the Mapepe Formation’s oceanic setting. What was a quiet precipitation of chert suddenly was torn apart and tumbled downslope. Was an earthquake to blame? A bolide impact? This is the result.
Journey to the Silurian period in what is today the Valley & Ridge province of eastern West Virginia to see some exquisite sedimentary rocks that represent deposition in a very arid, very shallow setting.
The Foreknobs Formation is a Devonian unit in the Valley & Ridge province of the Mid-Atlantic Region. It was deposited in relatively shallow near-shore conditions during the Acadian Orogeny. On a field trip to Corridor H, a new highway transecting the West Virginian Valley & Ridge province on Monday, I stopped to document a couple … Read more
Volcanic “hailstones” called accretionary lapilli rained down on South Africa 3 billion years ago, and have survived to be seen in the present day, along the R40 road through Barberton Mountain Land, near the Bulembu border crossing into Swaziland.
On the western coast of Islay, Saligo Bay showcases turbidites of the Neoproterozoic Colonsay Group. The Smaull Graywacke shows Caledonian (late Ordovician) folding and cleavage superimposed on world-class graded bedding. There’s also a nice dolerite dike to examine.
Remember the diamictite I featured here a few weeks ago, from Islay? It was the one that might be a Snowball Earth diamictite. Well, if you follow Snowball Earth science at all, you’ll doubtless be aware that the glaciogenic sediments are characteristically overlain by “cap” carbonates. There’s a stratigraphic successor to the Port Askaig Tillite, … Read more
What does the sedimentary record of a giant meteorite impact look like? Turns out it is full of tsunami breccia, fine ash, hail-like spherules, and a barium-rich ocean’s crystal precipitates. Join us in the Barberton Greenstone Belt of South Africa to learn more.
At the Volcano Museum in Stykkishólmur, I learned that Iceland has fossils. Specifically, they have a display of bivalve (clam) fossils there, and when I asked where to find them, I was directed to a point further east on the Snæfellsnes Peninsula. The next day, I set off to find them. Here was what I … Read more
Based on this photo, what do you think Stađarbjargavík might have to offer? If you guessed columnar jointing in basalt, you’d be right! Looking down the fjord, south of Hofsós (in Iceland): The place is basically a series of miniature Giant’s Causeways, full of unpopulated exemplars of cooling columns! Little coves separate the small peninsulas, … Read more
Since I showed off some Icelandic pillow basalts yesterday, today I thought I would showcase a new 3D model of big pillows in Columbia River basalt of eastern Washington, taken from a photo set I made when I was out there in May:
Time is short these days, but I know you hanker for amazing geology. How about some pillow basalts from the Snæfellsnes* Peninsula, far western Iceland? Note the cm-demarcated pencil for scale. See if you can find it in the GigaPan version below: Link Handheld GigaPan by Callan Bentley, stitched with Microsoft ICE _________________________ * “Snay … Read more
The news yesterday of 3.7 Ga stromatolites in Greenland prompts a closer look at 3.22 Ga microbially-induced sedimentary structures in the Barberton Greenstone Belt’s Moodies group sandstones.
In Cape Town for the International Geological Congress, Callan hikes up Table Mountain and finds some superb primary sedimentary structures in sands and shales of the Graafwater Formation.
This is the Split Rock at Clachtoll, on the shore of the North-West Highlands of Scotland. You’re looking out to sea, over the Minch. It’s the site that graces the cover of the excellent book A Geological Excursion Guide to the North-West Highlands of Scotland, by Kathryn Goodenough and Marten Krabbendam. “Clach toll” apparently means … Read more
Time for another virtual field trip on the Geologist’s Grand Tour of the United Kingdom: the most famous outcrop in the world. Today, we visit Siccar Point, Scotland. You’ve probably already seen photos of this place – they usually look something like this: To those who aren’t familiar, here’s what going on: There are two … Read more
Some of planet Earth’s best examples of basaltic cooling columns are found at the Giant’s Causeway in Northern Ireland. In this post, explore four different kinds of interactive digital media as a way of experiencing the Causeway virtually, from the comfort of your computer.
While soaking at some fine outdoor hot springs in southern Iceland (near Höfn) last week, I spied a Friday fold on the rock wall above the hot pots: Iceland is not a place where we would expect to find ductile folds in already-lithified rocks, so I’m guessing that these are folds related to flow in … Read more