Literally dig deeper into the earth surface and discover what is lying right under your feet.
Courtesy Kate HintzThe picturesque Tettegouche arch on Lake Superior's North Shore has finally collapsed. The oft-photographed rock-bridge was located in Tettegouche State Park near Illgen City, MN. Featured in the Science Buzz's Geology Safari, the arch withstood thousands of years of erosion, not to mention the constant tug of gravity since its formation. But sometime this past weekend it finally submitted to the elements.
Minneapolis Star Tribune
Courtesy Mark RyanAs Thor posted below, there’s been a whole lot of geological activity going on around the world lately what with all the large earthquakes and the volcano in Iceland spewing hot ash into the friendly skies. Luckily, Minnesota is situated on the very stable and essentially cold and dead North American craton. Devastating earthquakes and volcanoes are in our distant past, but that doesn't mean we don't get our share of geological action. Just last weekend I stumbled across evidence of a recent catastrophic event in one of St. Paul's parks.
I was out fossil hunting, scouring the sedimentary layers on the east banks of the Mississippi River. The strata there are the well-known record of the deposits of the Ordovician seas that once covered this part of Minnesota some 450 million years ago.
Courtesy Mark RyanIn the Twin Cities area, the base of the rock sequence is comprised of St. Peter sandstone, a soft and easily eroded rock that grades into a very thin layer of equally soft Glenwood shale. Immediately above those soft layers is the much more resistant Platteville limestone. The sandstone base has a habit of eroding away in the elements, often leaving a limestone overhang. Sooner or later, gravity wins out and the Platteville shelf collapses. This is what apparently happened in Hidden Falls Park in St. Paul recently. A whole lot of the limestone came crashing down, taking out some good-sized trees and blocking entry into the park. This gradual (and sometimes catastrophic) natural process has been going on for tens of thousands of years, ever since the glaciers exposed the layers. Usually, on our puny human timescale, it goes unnoticed. But it’s all part of the on-going rock cycle. Our famous Minnehaha Falls and its present location are the result of this relentless erosion process. As is St. Anthony Falls near downtown Minneapolis, which used to be located much farther down river from where it is today. In the process, the sandstone gets broken down into sand again, and the limestone blocks are eventually reduced to rubble. All of it will someday end up in the Gulf of Mexico unless some other forces intervene.
Courtesy Mark RyanI said earlier the scope of the rock slide impressed me, but maybe "unnerved" is a better word. I often scale the river bluffs looking for fossils, and I sure wouldn't want to be underneath something like this when the forces of nature decide to have it collapse. Across the river at Lilydale Regional Park there was an unfortunate incident several years ago when an overhanging shelf of limestone (in this case the Cummingsville member) fell and killed a fossil hunter. Luckily, no one was injured in the Hidden Falls event (at least as far as I know) but as you can see in the photos, there’s still quite a lot of the Platteville still up there, jutting out, and ready to come down at anytime. I wonder if the city of St. Paul plans to help it along? Whatever the case be careful when exploring along the river bluffs.
Courtesy WikipediaGeology may not be the "sexiest" of sciences, but when it gets cranked up, it can really make its presence known. And we've had a very interesting run of geological news in the past few months. The recent focus on earthquake matters is really summed up well in this commentary piece by Craig Childs of the Los Angeles Times.
Just in case you don't click the link, here are a few important notes from the piece to keep in mind while you're trying to figure out if the world is indeed coming to an end:
• With population increasing across the globe, more people are living in more hazardous regions.
• With our explosion of communications, we're hearing about earthquakes more often and in more depth.
• Since records have been kept on seismic activity, we know that about 50 earthquakes are recorded every day. Annually, the Earth averages 17 major earthquakes (7.0 to 7.9 on the Richter scale) and one doozy (8.0 or higher). The activity we've been seeing this year fits into those numbers so far.
Here are a few more items to points to take home regarding the recent geological frenzy:
As of Friday midday, the death toll in the China earthquake had climbed to over 1,100. While the devastation is much like the quakes in Haiti and Chile, the quake's cause, we're learning, was different.
Not all earthquakes start the same way. While most at the result of interactions between Earth's tectonic plates, this week's earthquake in China was different. It was an "intraplate" quake contained within an individual tectonic plate. Here's a full explanation. Basically, a quake occurs along a smaller fault that forms inside the plate, which is caused by other plates pushing on that plate's edges.
The New Madrid Seismic Zone in the central U.S., stretching from Arkansas to southern Illinois, is another example where "intraplate" earthquakes occur. On average, there's about an earthquake every-other-day in that zone, but they're very mild. But a large quake in the zone can spread damage over a much larger area.
Iceland's Eyjafjallajokull volcano continues to erupt and its ash continues to interrupt airline travel. Geologists have no idea how long the eruption might last. Back in 1821, the volcano erupted for several months. And the larger neighboring volcano, Katla, has not erupted yet. Typically it follows after Eyjafjallajokull's initial eruptions, and geologists say if that happens again, Katla could send out even greater amounts of volcanic ash.
A large earthquake occurred Sunday at 3:40 local time near the California-Mexico border. The powerful 7.2 magnitude quake was centered on Baja California about 110 miles east-southeast of Tijuana, Mexico. It was felt in Los Angeles and as far away as Las Vegas and Arizona. Dozens of injuries have been reported mainly in the town of Mexicali, Mexico (38 miles from the epicenter) where damage has been heaviest, but so far only two deaths are attributed to the quake. Several aftershocks have followed, and are expected to continue for days.
Courtesy Public domain via WikipediaBorn June 3, 1726 in Edinburgh, Scotland, Hutton was a physician, chemist, naturalist, and amateur geologist. He is considered the "father of modern geology" having formulated the theory of uniformitarianism, and its related notion of deep time. Hutton passed away on this day in 1797.
Iceland may be the Rodney Dangerfield of Europe – it just doesn't get no respect – but geologically it's at the epicenter of world attention these days. Iceland is in a volcano hot zone and an eruption Sunday of the volcano Eyjafjallajokull has garnered a lot of attention. Historically, every time Eyjafjallajokull erupts, the larger volcano Katla erupts soon after.
Below is aerial video shot by the Iceland Coast Guard showing Sunday's eruption. Stay tuned to see if there are more eruptions to come. Past eruptions of Katla, with lava and gases passing through Iceland's ice sheets, have created toxic smog that have damaged crops and sickened people in the British Isles. Here's the full AP report.
Courtesy Public domain via WikipediaToday marks the 163rd anniversary of the death of Mary Anning, early British fossilist who discovered the first complete remains of the marine reptiles ichthysaurus and plesiosaurus. Mary sold fossils she collected around Lyme Regis, England, to support her severely impoverished family after her father had died. She had no formal education, other than what her parents had taught her about collecting, but her fossils and knowledge of them were sought out by many of the top geologists of her time. Local folks viewed her activities with suspicion and apprehension since the biblical view of creation was still widely held, and the very idea that the fossils she collected were of creatures that went extinct was disturbing to many. Anning was made an honorary member of the Geological Society of England just prior to her death in 1847. Her portrait and some of the fossils she found are displayed in the British Museum in London.
Courtesy Wikimedia CommonsA massive earthquake occurred early this morning (1:34 EST) off the west coast of Chile some 70 miles NNE of the city of Concepcion. The powerful 8.8 magnitude tremor released about 500 times the energy generated by the recent 7.0 earthquake in Haiti. At least 78 people are reported killed, a number which will no doubt rise as information trickles in. Tsunami warnings have been raised across the entire Pacific Basin, including in Hawaii, Australia, and Japan.
Earthquakes are frequent in this area of Chile because it sets on a subduction zone where the Nazca Plate is pushing beneath the South American Plate. The region is also the location of the most powerful earthquake ever recorded on Earth, a 9.5 tremor that struck in 1960.