Stories tagged geology

Lilydale quarry: Located across the river from downtown St. Paul, Lilydale is probably the most famous fossil collecting site in the Twin Cities. Rock from the fossil-rich site was quarried by the now-defunct Twin Cities Brick Company and used for making bricks.
Courtesy Mark RyanEarlier this week a story appeared in the Minneapolis Star Tribune about fossil hunting in Lilydale Regional Park just across the river from the Science Museum. This has been a long-time favorite site to collect fossils from Minnesota’s ancient past. I’ve collected there often and at other sites around the region.

Fossil cephalopods: Specimen on the left was found at the Lilydale Quarry site. The slab on the right contains two small cephalopod fossils and was found near Shadow Falls in St. Paul, MN. Late Ordovician.
Courtesy Mark Ryan
Ordovician fossils: Typical fossil-filled shale slab found around the Twin Cities’ fossil collecting areas. Late Ordovician.
Courtesy Mark RyanAbout 450 million years ago, the North American continent was situated along the equator, and a warm shallow sea covered much of Minnesota. Sea life was abundant as confirmed by the tremendous amounts of marine fossils that be found around here. Rock formations of sandstone, limestone, and shale line the Mississippi River. The layers are flat and fairly undisturbed from when they were laid down during the Ordovician Period. Most of the fossils come out of the Decorah shale and Platteville limestone.

Shadow Falls: Marcus Kenney and sons Elijah and Benny hunting for fossils at Shadow Falls. The easily accessed site is located near the Mississippi at the west end of Summit Avenue in St. Paul, MN.
Courtesy Mark RyanI’ve been collecting fossils in this area for over three decades, and autumn has always been my favorite time to get outdoors, soak up some sun, and hunt for the elusive trilobite, or monstrous cephalopod (one of the largest found can be seen in the Science Museum’s Dinosaurs & Fossils gallery). You don’t really need much equipment, just a good eye, and maybe something to carry what you collect. Sometimes I like to have a mat or something to kneel on, but that’s me. I’ve been out quite a few times in the last six months and have found some very nice specimens.

Elusive trilobite: Molted trilobite tail. Trilobites are highly coveted by collectors. Late Ordovician
Courtesy Mark RyanThe Minnesota Geological Survey has plenty of information about Minnesota’s geology and prehistoric past. Click on the link to download their publication titled Fossil Collecting in the Twin Cities Area. It includes various collecting sites around southeastern Minnesota and illustrations of the fossils you’re likely to find there, such as bryozoans, brachiopods, gastropods, trilobites, horn coral, pelecypods, and cephalopods.

LINKS
Fossil collecting Lilydale Regional Park (pdf file)
Minnesota Fossils
More trilobite info
List of fossil sites and equipment
More about horn coral

Roadside attraction: Pat Ryan hunts for fossils in the Decorah shale outcropping in a highway ditch near Cannon Falls, MN. The highly fossiliferous site is located about 2 miles southeast of the town center.
Courtesy Mark Ryan
More than enough fossils: Close-up of fossils littering the ditch near Cannon Falls, MN. Fossils at this site are found mostly weathered out of the matrix allowing for the collection of some great individual specimens.
Courtesy Mark Ryan

Trapped in time: Fossil of a cephalopod (possibly baculites?) in situ, near Cannon Falls, MN. Late Ordovician.
Courtesy Mark Ryan
Fossil of Ordovician predator: Fossil cephalopod (possibly baculites?) collected near Cannon Falls, MN. Late Ordovician. Baculites were ammonites with a straight tusk-like shell. The cephalopods occupied the top of the food chain during the Ordovician.
Courtesy Mark Ryan
Fossil coral: Fossil coral (Favosites?) found near Cannon Falls, MN. Late Ordovician. Other than cephalopods, this is the largest single fossil I’ve ever found in the Decorah shale. I believe it’s some sort of striated coral.
Courtesy Mark Ryan
Lots of fossils: Bryozoa litter the ground at an exposure near Cannon Falls, MN. Bryozoa were microscopic animals that often formed coral-like colonies or fan structures and are the most common fossils found in the Decorah shale around southeast Minnesota.
Courtesy Mark Ryan
Down and dirty: Pat Ryan digs out a cephalopod fossils found on the flats of a Decorah shale exposure near Cannon Falls, MN.
Courtesy Mark Ryan
Close-up of cephalopod: Large cephalopod segment found by my brother Pat at Decorah shale exposure near Cannon Falls, MN. Another piece of the same specimen was found about 2 feet away.
Courtesy Mark Ryan
Rare find: Trilobite head in matrix, found near Cannon Falls, MN. Late Ordovician. Heads of the ancient arthropods are extremely rare. This is only the second trilobite head I’ve found in three decades collecting fossils around the Twin Cities
Courtesy Mark Ryan

Tags : paleontology, Ordovician Period, Minnesota fossils, geology, fossils

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Say you want to walk on the oldest rocks on the surface of the Earth. Well, it turns out that Canada is the place to go. Recently, Science magazine has reported that researchers have found rocks in Quebec that could be as old as 4.28 billion years old. Yes, billion. 4,280,000,000. Now, keep in mind that the Earth is estimated to be around 4.6 billion years old. There are at least three pretty neat points to make here:

1. It is harder than you think to find really old rocks, as most of the crust of the Earth is constantly recycling itself, courtesy of plate tectonics. Fortunately, there is not a great deal of tectonic activity happening in Canada, thus keeping these rocks at the surface.

2. 4.28 billion years old is pretty darn old. Think about it this way; this post is 2,129 characters long. That includes all of the letters and spaces. We will pretend that the very first characters of this post are the youngest, and the ones at the end are the oldest. Humans, which we will understand to be modern Homo sapiens, have only been around for approximately 40,000 years, which would be the very top of the "S" in "Say" that started this post. That is not even one full letter! These rocks have been around for all but the very last sentence of this post. That is a lot of characters/time.

3. They say that these could be the oldest rocks, as old as 4.28 billion years old, but... Dating of really, really old things like this use a technique known as radiometric dating. This type of dating does not give a specific date for the object in question, but rather, a range of dates. So these samples have dates ranging from 3.8 to 4.28 billion years old. The previously known oldest rock samples, also found in Canada, have dates that could be as old as 4.03 billion years old. So... these recently found rocks, if they are actually towards the younger end of their date range, could actually be younger than the potentially 4.03 billion years old rock that was already found.

No matter what, these rocks are still very exciting and can tell us some interesting things about the formation of the Earth's crust!

Tags : oldest rocks, geology, Canada, billion, dating, age

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Where will we get the energy we need for the future?: Some people would like to see more oil drilling in the US.
Courtesy L. Gnome

(With the Republican National Convention literally across the street, the Science Museum of Minnesota will be closed starting Friday, August 29. But Science Buzz marches on! To honor our convention guests, I’ll be posting entries focusing on issues where science and politics overlap. Hopefully this will spur some discussion. Or at least tick some people off. This is the last entry in this series. Previous entries here, here, here, here, here and here.)

Energy is one of the big issues in this election cycle. With gasoline at record high prices, and much of the world’s oil lying in politically unstable regions, there is a lot of pressure to do more drilling in the US, open up more areas to exploration, and build more refineries.

Meanwhile, many conservation groups oppose more drilling, especially offshore or in ecologically sensitive regions of the Arctic. Some call for conservation measures to help reduce oil consumption.

(While the Science Museum of Minnesota does not endorse any candidate or platform, I personally like this energy plan.)

The Bureau of Land Management has announced that a major source of oil is sitting right below our feet: oil shale. Shale is a fine-grained rock made of compressed clay or mud. In some place, oil seeps into the rock. This oil is much more difficult to extract than free-flowing liquid petroleum. But with gas at $4 a gallon, it is becoming feasible to squeeze oil from the rock.

The government estimates there could be up to 800 billion barrels of oil sitting beneath Colorado, Utah and Wyoming. This is equivalent to our current oil imports for, roughly, 219 years. So, tapping this resource would go a long way toward meeting our energy needs until other, greener sources (wind, cheap solar, non-food ethanol) come on-line.

The Bureau of Land Management has produced preliminary guidelines for regulating commercial oil shale production. They are prohibited by law from producing final guidelines. The President has asked Congress to lift the ban so that this effort may go forward.

Tags : politics, energy, oil, petroleum, shale, geology, kerogen

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Goodness, gracious, here they come!: No reason to panic. Just think of them as giant parakeets that could swallow you whole.
Courtesy Mark RyanNo, this isn’t about the herds of conventioneers descending upon the Saintly City for the Republican National Convention next fall. That would be disrespectful. I’m talking about the dinosaurs coming in June for five days at the Xcel Energy Center in a show called “Walking with Dinosaurs: The Live Experience“.

These aren't the same dinos that overran the Twin Cities last year during the Science Museum's 100th anniversary celebration. These latest dinosaurs are from Immersion Edutainment, an Australian company that uses a mix of computers, hydraulics, puppets, and actors to create a live show based on the highly acclaimed BBC television series by the same name.

And just in case you’re worried, these aren’t going to be cuddly and lame purple dinosaurs dancing about on ice, or jerky, hard-cased theme park animatronics, or even colorful plaster statues– no siree Bob – these are going to be scientifically accurate Mesozoic behemoths complete with life-like flexible skin, rippling muscles, swinging tails, snapping jaws, and heart-pounding sound-effects that will shake your popcorn right out of its box.

During the 90-minute show, a “paleontologist” serves as ringmaster and narrator, offering scientific insights into the world of these fantastic creatures. Geological concepts such as plate tectonics and continental drift help put things in perspective, as ten dinosaur species are presented in their proper order from the late Triassic to the late Cretaceous, including two enormous Brachiosaurs and everyone’s favorite, Tyrannosaurus rex. This is going to be one really BIG show!

Music and video projection will add to the dramatic content of the presentation and the program is deemed appropriate for all ages although some scenes could be a bit too intense for some very small kids.

Hoards of Australians evidently flocked to this thing when it toured sports arenas there. Performances here run June 11-15 at the Xcel Energy Center. And if 90 minutes of dinosaurs running amok aren’t enough for you, after the show, you can scoot across the street to the Science Museum and see the remains of some real dinosaurs. What could be better than that?

All the information you need about “Walking with Dinosaurs: The Live Experience” can be found at the Immersion Edutainment website.

Tags : prehistoric animals, paleontology, geology, dinosaurs, dinosaur show

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Go to learn more about rocks and minerals:
http://en.wikipedia.org/wiki/Rocks_and_minerals

Tags : rocks, minerals, geology

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Red Rock Canyon: The gray Paleozoic limestones of the Spring Mountains loom over the younger Mesozoic sandstones.
Courtesy Mark RyanEven when I’m on vacation my attention is often drawn to things of science. Last week after a couple rigorous days in Las Vegas observing the various aspects of the Law of Attraction (“please make the next card an eight”) and my personal experiments in slot-machine probability and statistics, my wife and I took a break from all the razzle-dazzle to investigate a geological feature situated in the Spring Mountains about 20 miles west of the city.

Another view of Red Rock Canyon: The sandstones dwarf visitors in the distance.
Courtesy Mark RyanRed Rock Canyon National Conservation Area covers 197,000 acres within the Mojave Desert and the namesake formation stands out colorfully against the stark grayness of the basin and range topography for which Nevada is so well known. The park offers plenty to do and see: hiking, rock-climbing, petroglyphs, petrified wood, desert flora and fauna, and a 13 mile highway loop for driving or biking. Wild burros run free in the park but we didn’t see any while we were there.

Half a billion years ago the region was under a vast ocean densely populated with Paleozoic Era marine life. More than 9,000 feet of limestone and other carbonate rocks formed out of this environment and remained buried deep beneath the Earth for millions of years. Later when the oceans receded due to the seabed rising, swamps appeared and disappeared, and for a while the area was heavily forested as evidenced by petrified wood found there. Ephemeral waters left behind gypsum and salt as they evaporated. At some point, oxidation of iron-bearing minerals in the sediments took place producing the reddish colors apparent in the canyon today. On top of all this (following the Law of Superposition), massive windblown sand dunes shifted over the region at a time when it resembled today’s Sahara Desert. The dunes themselves were eventually buried and hardened into layers of sandstone.

During the Laramide Orogeny tectonic forces deep within the Earth’s crust began to crumple the landscape as predecessors to the Pacific Plate collided and subducted with the North American Plate and caused the older Paleozoic limestone to heave above the younger Mesozoic sandstone.

Impressive example of cross-bedding: Red Rock Canyon sandstone shows the effects of wind on the sand dunes from which it was formed.
Courtesy Mark RyanKnown as the Keystone Thrust Fault, it’s one of the best visible examples of such a geological feature, due to the stark color difference between the rock units involved.

The canyon’s calico-colored cliffs and boulders also display some really fine examples of cross-bedding, which can form in environments where water or wind flows over sand or gravel beds. The sand dunes that existed at Red Rock during the Jurassic Period were such an environment. We hiked up the rocks for a spell, and although, it’s fairly steep in places, the rough sandstone surface provided a very secure footing.

So, if you’re out Vegas way, I recommend you take some time away from all the artificial glitz and glitter to drive out and blow some cash ($5 per private vehicle) to view some of the dazzling natural glitz abundant at Red Rock Canyon.

LINKS
Red Rock webcam
More on thrust faults
More on the Keystone Thrust Fault

Tags : thrust fault, tectonics, geology, fault

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