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Charles Carrigan
14,773 followers -
Husband, Father, Geoscientist, Educator
Husband, Father, Geoscientist, Educator

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Fossil Meteorite with Cephalopod at the Field Museum

Meteorites that are found have generally fallen out of the sky in the not to distant past. That doesn't mean that they haven't fallen throughout Earth's history, of course, and old meteorite impact sites are well known in the rock record. But the meteorites themselves that fell millions of years ago are pretty rare, because they weather away fairly easily at Earth's surface. A few, however, have been preserved in the ancient rock record as "fossil" meteorites. This one on display at the Field Museum is preserved in a Devonian limestone. The weathering rind is pretty thick, even being encased in the limestone. Some minerals in meteorites, like the spinels, are much less susceptible to weathering and last longer than the olivine, iron, and pyroxenes that dominate chondrites. This one is also special in that it also preserves a beautiful, large cephalopod.

#Geology #Paleontology #Meteorites #FieldMuseum #Science #Nature 
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#FridayFold today is from the Black Hills of SD

The Black Hills expose an old Precambrian area of metamorphic rocks that are complexly deformed. They were brought to the surface relatively recently during the same mountain building event that uplifted the Rocky Mountains much farther to the West. These thin layers are bent back on themselves so much that if you didn't see the hinge you'd have a hard time knowing they were even folded. Since both limbs of the fold would measure at the same angle, this kind of fold is called isoclinal.

#GeologicStructure #Science #Nature #OptOutside #PostMoreRocks #Geology 
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Feb. 2017 was the 2nd warmest Feb ever directly measured, in 137 years.

This wouldn't be news IF the number of cold records being broken were anywhere close to the number of warm records. But warm records just keep getting broken, year after year, month after month, region after region. The pattern of warming is undeniable.

https://data.giss.nasa.gov/gistemp/news/20170315/

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New Sm-Nd isotope data from really old Canadian rocks (~2.7 Ga) suggest that they formed from a precursor rock that would have been extremely old >~4.3 Ga basaltic crust. If so, that basaltic crust would have sat around on the Earth's surface for an extremely long time, suggesting therefore that plate tectonics did not exist in the early history of the Earth.

https://www.sciencenews.org/article/remnants-earths-original-crust-preserve-time-plate-tectonics

If you want the Science article, it is here: http://science.sciencemag.org/content/355/6330/1199
Abstract: "Geologic processing of Earth’s surface has removed most of the evidence concerning the nature of Earth’s first crust. One region of ancient crust is the Hudson Bay terrane of northeastern Canada, which is mainly composed of Neoarchean felsic crust and forms the nucleus of the Northeastern Superior Province. New data show these ~2.7-billion-year-old rocks to be the youngest to yield variability in neodymium-142 (142Nd), the decay product of short-lived samarium-146 (146Sm). Combined 146-147Sm-142-143Nd data reveal that this large block of Archean crust formed by reworking of much older (>4.2 billion-year-old) mafic crust over a 1.5-billion-year interval of early Earth history. Thus, unlike on modern Earth, mafic crust apparently could survive for more than 1 billion years to form an important source rock for Archean crustal genesis."

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Remnants of the Ice Age

The Grand Tetons are currently home to a single remaining glacier, but in the past there were quite a few. Here the upper bowl (called a cirque) between the high peaks, where ice would have accumulated, is still visible, with snow covering it and the glacial valley below. However, by summer's end, this one will not retain enough ice to accumulate mass on an annual basis, and so the yearly snows temporarily fill what was once a continually flowing mass of ice.

#Geology #Nature #IceAge #Science #ScienceEducation #Glacier #GrandTetons 
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TouchTerrain is a new web app that is a super easy way to find an area of the world and get a file created that can be used in a 3D printer in order to replicate topography. 

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Fossil Octopus at Dice Museum

Earlier this week I mentioned that I had a chance to visit the Dice Museum at Calvin College last week. They have an exceptional mineral collection, but they also have a few incredible fossils, like this one. Soft-bodied organisms are rarely preserved in the fossil record, but a few do manage to get preserved. Octopi fossils are so rare that there are only about half a dozen in the world!

#FossilFriday #Paleontology #Geology #Science #Nature 
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Fellow Geos-

What do you use to take trip stops/points of interest with you into the field? What device do you use? Have a favorite app or apps? How intuitive is it? Paper maps or electronic?

Personally I'd really like to go full electronic. But it needs to be easily accessible and easy for students to pick up quickly. I've tried a lot of different apps and I don't feel like I've found the right solution yet. I really like Google's MyMaps for easy and intuitive creation of maps of POIs, but it has no offline support for the times when I'm out in the field and data connections are limited. And it has no iOS app, which makes it more difficult to share a map with students and have them open it on their phones or tablets.

Thoughts? What do you use to get out and get there? 

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En Echelon Tension Gashes in the Van Hise Rock

This structure is a classic one that all geoscience students work to understand. The structure consists of a series of ~parallel veins, in this case white quartz. The parallel veins each pinch out on their ends, and they are staggered along a diagonal line in an en echelon pattern. From this structure one can work out the orientation of the 3-D stress field that produced it. The veins are formed when cracks open up in the rock and fluids precipitate new mineral matter. The direction of greatest stress was oriented parallel to the veins, while the direction of least stress was oriented perpendicular to the veins. The diagonal along which the veins are staggered is a zone of shearing, with the material above it moving down to the left relative to the material below moving up and to the right. There is not much offset in these types of shear zones; most of it is taken up by the small amount of extension in each individual vein. One might think of these as "proto-faults"; continued shearing might eventually tear a fault surface through the rock and sliding along it could begin. So, geostudents, if this process were to continue and form a fault, what kind of fault would it become?

#Geology #Nature #Science #GeologicStructure #Tectonics #VanHiseRock 
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An excellent summary of the challenges of water pollution in the Mississippi River system. 
The Challenge of Tracking Nutrient Pollution 2,300 Miles: In the “Land of 10,000 Lakes,” Minnesota relies on clean water for recreation, drinking water, abundant fish and wildlife habitat, and productive agriculture. “Fishable and swimmable waters are an important part of our economy, yet high levels of nutrients in our waters can impact these activities,” said David Wall, a researcher at the Minnesota Pollution Control Agency. “We have over 500 lakes and quite a few rivers impaired due to phosphorus. When we have nutrient problems here, they can leave Minnesota's borders and flow downstream to people in other cities that need clean water, too.” Each spring, water flows approximately 2,300 miles down the Mississippi River, beginning its journey at Lake Itasca in northern Minnesota and emptying into the Gulf of Mexico. Along the way, streams and rivers accumulate nutrients that run off the land and into the waterways, and eventually these nutrients enter the Gulf of Mexico. Spring pulses of nutrients to the Gulf contribute to the second largest hypoxic—or low oxygen—zone in the world. In 2016, the estimated size of the hypoxic zone in the Gulf of Mexico was 5,898 square miles, approximately the size of Connecticut. The Gulf is an important commercial and recreational fishery, providing over a billion pounds of commercial fishery landings each year, which yield an estimated value of $662 million. Hypoxia can affect this aquatic life by reducing growth and reproduction. Streams in the Midwest Corn Belt region in Iowa, Illinois, and Indiana contribute high amounts of nitrogen to local streams and ultimately to the Gulf of Mexico. Photograph credit: Pete Van Metre, USGS To prioritize mitigation actions, it is critical to better understand nutrient sources. Identifying these sources is a complicated task because, at more than 1.2 million square miles, the Mississippi River Basin is the fourth largest basin in the world. It covers close to 40 percent of the lower 48 States. There are 31 States that drain, via the Mississippi River Basin, into the Gulf of Mexico, and nutrient sources are found throughout the basin. “Fertilizers used on crops, air pollution, and manure are some of the major sources of nitrogen transported from the Mississippi River Basin to the Gulf of Mexico,” said Michael Woodside, a hydrologist with the U.S. Geological Survey (USGS). One of the tools Minnesota officials use to compare watershed nutrient loads is the Spatially Referenced Regression on Watershed Attributes model, or SPARROW model, developed by the USGS. “Minnesota used USGS SPARROW model results, along with other data, to inform our State-level nutrient reduction strategy and to prioritize watersheds,” said Wall. “Additionally, we used the model in combination with other modeling tools to help set goals and targets for nutrient reductions and to evaluate load reductions expected at the State borders.” “There are two web-based applications for exploring SPARROW results,” said Woodside. “First is a mapper that helps identify nutrient hotspots, the largest sources of nutrients, and how they move downstream. Second is a decision support tool that allows users to zoom into any stream or reservoir to learn about nutrient sources. The tool can be used to provide science-based information for questions like, ‘How much will nutrients be reduced to my reservoir if fertilizer inputs in the watershed are reduced by 20 percent?’” Maps tracking the sources and quantities of nutrients to all of the Nation’s estuaries and Great Lakes are available online. Information gathered using SPARROW is a critical piece of the puzzle, but only one piece. SPARROW helped Minnesota make great strides by identifying priority watersheds and beginning nutrient reduction actions, but moving forward requires a collaborative effort from numerous partners. The Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, comprising States and Federal agencies such as the USGS, works collaboratively to minimize the nutrients entering the Mississippi River and reduce the size of the hypoxic zone in the Gulf. The task force is reaching out to new partners, such as universities, agricultural organizations, and communities, to address science, social science, and outreach needs. The SPARROW model relates information on nutrients from agricultural, urban, and atmospheric sources to water quality data at monitoring stations to describe how nutrients move from the land to streams, reservoirs, and estuaries. Credit: USGS (Public domain.)   #usgs #news
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