Friday fold: blueschist & eclogite at Jenner, California
A pre-Fall Meeting field trip to the coast of northern California yields rare sights of garnet-bearing blueschist, plus eclogite, some pillow basalts, birds, waves, wind, and a lot of rain.
basalt
Geology of the Galapagos Islands
Dozens of delectable geological images from the Galapagos Islands, showing fluid basalt flows and violent pyroclastic deposits along with many primary volcanic features (and a bit of sedimentology thrown in for good measure).
Mafic volcanics atop felsic instrusives: Sonora Pass, California
Sonora Pass, California, is a lovely place to examine a volcanic-on-plutonic nonconformity that spans about 80 million years of missing time. Let’s check it out on a photo-rich virtual field trip!
Friday fold: bend in a vesicular lava flow, Etna
It’s the First Friday of Fall! Here’s a sort of fold to help you celebrate: a section through a ∧ shaped bend in a vesicular basalt flow from the eastern flanks of Mount Etna in Sicily. It’s due to volcanic lava flowing rather than ductile deformation of a pre-existing solid rock (our usual habit with … Read more
Basaltic strata, faulting, and glaciation in western Iceland
Today, let’s journey to Iceland, to a bit northwest of Reykjavík. This is a view from the top of the Grábrók cinder cone, across the valley to the east. With very few exceptions, Iceland is a big pile of basalt, and that shows through in the walls of this valley, which display a stack of … Read more
Y-shaped joints on a basalt flow, Lake Mývatn, Iceland
A basalt flow in Iceland shows both enticing pahoehoe and fractures with a Y-shaped intersection pattern. Comparisons to bread loaves and east Africa suggest a reason why.
New digital media of Shenandoah National Park feeder dikes
In Shenandoah National Park, astride Virginia’s Blue Ridge, feeder dikes of Catoctin Formation (meta-)basalt cut across the Grenvillian-aged granitoid basement. Due to their mafic composition and columnar jointing, these feeder dikes generally weather more rapidly than their host rocks. I led a field trip in the park on Thursday for my son’s school, and my … Read more
Oddball Icelandic rocks, part I: A green ignimbrite
Iceland does basalt really, really well. But there are a few non-basaltic igneous rocks to be found there, too. One of them is a green ignimbrite (pyroclastic conglomerate) that crops out in coastal Berufjörður, eastern Iceland. Check it out!
A virtual field trip to Rathlin Island, Northern Ireland
Rathlin Island lies north of mainland Northern Ireland, a few miles offshore. I spent three lovely days there this past summer, investigating the geology and appreciating the wildlife (puffins and other sea birds, and seals). The geology is pretty straightforward: Paleogene basalt overlying Cretaceous “chalk” (really not so chalky here – technically, it’s the Ulster … Read more
Stađarbjargavík
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
Pillow basalts from eastern Washington: a 3D model
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:
Pillows in Icelandic basalts
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
A virtual field trip to the Giant’s Causeway, Northern Ireland
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.
3D model of onion-skin weathering
I collected a photo set at the Giant’s Causeway to show the “textbook” examples of spheroidal (“onion skin”) weathering exposed on the road down to the causeway. My student Marissa Dudek used the photo set and Agisoft Photoscan to make a great 3D model of the site. She posted it on Sketchfab yesterday evening. Check … Read more
Two virtual weathered-out dikes in a fjord in eastern Iceland
Two 3D models for you today, both produced by my student Marissa Dudek, using photo sets I gathered in Iceland: Photoscan model by Marissa Dudek (That one has paleomag holes drilled into it!) Photoscan model by Marissa Dudek (That one I’m particularly pleased with. Given the circumstances of image acquisition, this is a very good … Read more
Friday fold: isoclinal flow structures in Icelandic lava
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
Dimmuborgir, Lake Mývatn, Iceland
Last week, I was in Iceland, driving around the country’s Ring Road and checking out its amazing geology with my family. We had a great time in particular exploring in the Lake Mývatn region, on the country’s subaerial expression of the Mid-Atlantic Ridge. Lake Mývatn itself is in a rift basin, peppered with a great … Read more
Flood deposits of Glacial Lake Missoula outburst floods
Two weeks ago, I went on an awesome, informal field trip to eastern Washington State to visit the Channeled Scablands for the first time. My collegue Bill Richards of North Idaho College picked me up in Spokane and drove me halfway across Washington and back to Moscow, Idaho, over the course of a day. This … Read more
A baked horizon in the Columbia River flood basalts
How did this bold orange layer develop? It’s seen in an outcrop near Wilson Creek, Washington, in the Columbia River basalts.
Pillow basalt exposures in the Columbia River basalts
Pillow basalts form when mafic lava erupts underwater. Here are several examples from the Miocene Columbia River flood basalts, a large igneous province in eastern Washington state.