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#MinCup
Zircon is a Zr-silicate mineral that's exceptional as a tool for dating rocks. It incorporates lots of radioactive elements U & Th, and excludes the daughter product, Pb, allowing vary accurate measurements of the ages of samples. It is found in nearly all types of igneous rocks, as well as many metamorphic and sedimentary ones. It is extremely durable during geologic events - it can survive intense chemical weathering, long journeys as grains of sand bouncing down a river system, extreme temperatures, and even melting events where other minerals turn to magma. Those complex histories are often recorded within a single grain, as new events produce overgrowths of new zircon on the outside of older grains. For years, this was a problem for geochronologists because ages of zircons always produced mixed results. But several decades ago, the technique to date individual spots in a single crystal was developed, and this advancement revolutionized our understanding of Earth's history. Since then, hundreds of thousands of individual zircon crystals have been analyzed across the world as Geologists seek to better understand how our planet works and has developed over time. Here are three images of zircons that show beautiful internal zoning with some spot ages. The first one came from my MS thesis; it was the grain that first revealed to our research group that the main mountain building event in the Southern Appalachians was much younger than most people had previously thought.
Over on Twitter, fellow mineral enthusiasts have been holding the #MinCup competition, voting each round for their favorite minerals until the winner is decided. Today is the final, and it's come down to olivine vs. zircon. It's been a great outreach & communication opportunity for scientists to share amazing facts about minerals and what we can learn from them. You can probably guess which mineral I voted for!
#TeamZircon #PostMoreRocks #geology #mineralMonday

Somebody said it was #InternationalRockDay but all the posts under the hash tag are 🤘 & 🎸. Here's a gorgeous garnet mica schist from the Dice Museum. Specimen from Wrangell Island, Alaska.
#PostMoreRocks #GeologyRocks #🤘

It's Friday!!! This #FridayFold is from the Bighorn Mountains of Wyoming, where highly deformed Archean gneisses are exposed. These rocks are the roots of an ancient mountain belt, formed when the N. American continent was still in it's infancy. Blocks of crust of different ages collided with one another through tectonic movements if the Earth's lithosphere, and slowly accreted together.
#PostMoreRocks #Geology #BighornMountains

A Dinosaur's Nightmare.
An iron meteorite showing the Widmanstatten pattern, on display at Chicago's @fieldmuseum .
The pattern is composed of two metal alloys of iron and nickle. The first, called taenite, is present when the metal is at high temperature. As the metal cools, the taenite must have a higher % of Ni to continue to be stable. The excess Fe forms a second Fe-Ni alloy called kamacite, which has a lower Ni:Fe ratio. To grow crystals of kamacite this large requires a very slow cooling rate, somewhere around a couple million years. For these materials to cool this slowly, they would have had to have been part of the core of a fairly large planetary body in the past, likely somewhere in the asteroid belt. This planetoid would have then been broken apart, likely through collisions with other asteroids, before finally hurtling through space on a collision course with Earth.
#meteorite #widmanstatten #STEMEducation #FieldMuseum #PostMoreRocks

Folded banded-iron formation at Dice Museum.
Banded iron formation begin as sedimentary rocks formed in the ancient oceans. They consist of layers of iron oxide minerals and quartz. Their formations are related to the build up of oxygen in Earth's atmosphere in the ancient past by the earliest photosynthetic organisms. Later, the rock was buried, metamorphosed by heat and pressure, and deformed into this folded structure. This beautifully cut and polished specimen is on display at the Dice Mineral Museum at Calvin College. The back lighting allows the red and yellow colors to done vibrantly.
#FridayFold #DiceMuseum #bandedironformation #geology #PostMoreRocks

Selenite gypsum at the Dice Museum, Calvin College. Specimen is from Chihuahua, Mexico. The clarity of these is well demonstrated by the back lighting.
#OnMondaysWePostMinerals #PostMoreRocks #MineralMonday #geologyrocks

Fossil Meteorite with Cephalopod at the Field Museum
Most of the meteorites we have to study fell out of the sky in the not too distant past. Meteorites that feel a lot time ago, geologically speaking, are really rare. That doesn't mean that rocks from space haven't fallen to Earth throughout its history, of course; in fact old meteorite impact sites are well known in the rock record. Big meteorites often vaporize on impact, and small ones weather away quite easily at Earth's surface. There are a few, however, that 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 with the alien rock encased in another stone. 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, which happened to also get fossilized very near the meteorite.
#Geology #Paleontology #Meteorites #FieldMuseum #Science #Nature #PostMoreRocks

Wave cut cliff and marine terrace at Sunset Cliffs Natural Park, Point Loma, CA.
A few years ago I had the opportunity to visit one of our sister schools in Point Loma, CA, for a conference. I took the opportunity to visit this fantastic City Park on the coast of the Pacific Ocean - what a sight! The rocks exposed here are the Point Loma formation, a late Cretaceous sequence of sandstones, siltstones, and shales. Down below, the rock layers are being actively eroded by the wave action, forming a fairly flat platfom. Above, where I was standing, is another flat platform, but this one was uplifted by tectonic activity and is now a marine terrace. It's so secret that southern California is an active seismic zone, and this landscape is a testament to the Earth's power. According to the sources I've read, the uplift occurred at a maximum of about 6" per millennium in the mid-late Pleistocene (~780 ka - ~12 ka) due to motion on the Rose Canyon fault.
#geologyrocks #PostMoreRocks #pointloma #sunsetcliffs #tectonics #marineterrace

The serpent's head. #FridayFold
Last week I shared a photo of one of the "tails" of the dragon, a "famous roadcut" up in the Grenville of Ontario, CA. This is the head of the beast. The black layers are amphibolite rock that has been "mixed in" with a pinkish-gray granitic gneiss. The whole area was caught up in a shear zone, which is like a fault but much deeper in the Earth's crust, where rocks become subject to ductile processes of deformation, bending instead of breaking. The amphibolite is like a spaghetti noodle getting wound up on a spinning fork, folded back and forth over itself many, many times. At this time, the Grenville Mountains had formed, a chain of thickened crust that would have rivaled the modern day Himalayas. These rocks were somewhere on the order of 30 km deep at that time, so the Grenville Terrane of Eastern Canada gives geologists a look into what the deep parts of mountain belts are like.
#geologyrocks #tectonics #grenvilleprovince #ohrocks #postmorerocks #heretherebedragons #GeologicStructure

MOST RECENT

One last shot from my trip to Sunset Cliffs Natural Park. The strata here were deposited in the Late Cretaceous, and are called the Point Loma Formation. They consist of sandstones, shales, and siltstones. Dinosaur remains have been found in these rocks, including partial specimens of hadrosaurs and ankylosaurs.
#PointLoma #SunsetCliffs #PostMoreRocks #dinosaurs #Mesozoic #FossilFriday

Waves slowly eroding a pair of small sea stacks at Sunset Cliffs Natural Park. Another shot from my trip to Point Loma, CA, a few years ago. Wave action slowly erodes bedrock by stirring up sand, which then grinds away at the bedrock by slow abrasion.
The Pacific Waves sounds like a good band name, don't you think?
I shot this with a 1/100 shutter speed, which served to freeze most everything in the shot, but to also capture the wave cresting over the rocks with a slight bit of motion blur. As the water spilled over the rock, it was moving just a bit faster there than elsewhere.
#GeologyRocks #PointLoma #SunsetCliffs #PostMoreRocks #erosion

Wave cut cliff and marine terrace at Sunset Cliffs Natural Park, Point Loma, CA.
A few years ago I had the opportunity to visit one of our sister schools in Point Loma, CA, for a conference. I took the opportunity to visit this fantastic City Park on the coast of the Pacific Ocean - what a sight! The rocks exposed here are the Point Loma formation, a late Cretaceous sequence of sandstones, siltstones, and shales. Down below, the rock layers are being actively eroded by the wave action, forming a fairly flat platfom. Above, where I was standing, is another flat platform, but this one was uplifted by tectonic activity and is now a marine terrace. It's so secret that southern California is an active seismic zone, and this landscape is a testament to the Earth's power. According to the sources I've read, the uplift occurred at a maximum of about 6" per millennium in the mid-late Pleistocene (~780 ka - ~12 ka) due to motion on the Rose Canyon fault.
#geologyrocks #PostMoreRocks #pointloma #sunsetcliffs #tectonics #marineterrace

#MinCup
Zircon is a Zr-silicate mineral that's exceptional as a tool for dating rocks. It incorporates lots of radioactive elements U & Th, and excludes the daughter product, Pb, allowing vary accurate measurements of the ages of samples. It is found in nearly all types of igneous rocks, as well as many metamorphic and sedimentary ones. It is extremely durable during geologic events - it can survive intense chemical weathering, long journeys as grains of sand bouncing down a river system, extreme temperatures, and even melting events where other minerals turn to magma. Those complex histories are often recorded within a single grain, as new events produce overgrowths of new zircon on the outside of older grains. For years, this was a problem for geochronologists because ages of zircons always produced mixed results. But several decades ago, the technique to date individual spots in a single crystal was developed, and this advancement revolutionized our understanding of Earth's history. Since then, hundreds of thousands of individual zircon crystals have been analyzed across the world as Geologists seek to better understand how our planet works and has developed over time. Here are three images of zircons that show beautiful internal zoning with some spot ages. The first one came from my MS thesis; it was the grain that first revealed to our research group that the main mountain building event in the Southern Appalachians was much younger than most people had previously thought.
Over on Twitter, fellow mineral enthusiasts have been holding the #MinCup competition, voting each round for their favorite minerals until the winner is decided. Today is the final, and it's come down to olivine vs. zircon. It's been a great outreach & communication opportunity for scientists to share amazing facts about minerals and what we can learn from them. You can probably guess which mineral I voted for!
#TeamZircon #PostMoreRocks #geology #mineralMonday

Tilted layers of Cretaceous Dakota sandstone at Dinosaur Ridge, CO.
#geology #Cretaceous #sandstone #DinosaurRidge

A Dinosaur's Nightmare.
An iron meteorite showing the Widmanstatten pattern, on display at Chicago's @fieldmuseum .
The pattern is composed of two metal alloys of iron and nickle. The first, called taenite, is present when the metal is at high temperature. As the metal cools, the taenite must have a higher % of Ni to continue to be stable. The excess Fe forms a second Fe-Ni alloy called kamacite, which has a lower Ni:Fe ratio. To grow crystals of kamacite this large requires a very slow cooling rate, somewhere around a couple million years. For these materials to cool this slowly, they would have had to have been part of the core of a fairly large planetary body in the past, likely somewhere in the asteroid belt. This planetoid would have then been broken apart, likely through collisions with other asteroids, before finally hurtling through space on a collision course with Earth.
#meteorite #widmanstatten #STEMEducation #FieldMuseum #PostMoreRocks

really pretty rocks, a beautiful lake, and once again smoke @ Lake McDonald, Glacier NP 🙌 #lookslikepetkibble #foramtravels #glaciernationalpark #glacier #np #usa #warmmilk #lakemcdonald #PostMoreRocks #geology

The Grand Tetons behind the Moulton Barn. The Tetons are some of the youngest mountains in the greater Rocky Mountain chain. They were uplifted in the last 10 million years due to motion on the Teton fault, a normal fault that runs 44 miles along the east side of the Tetons. The fault is still active, moving an average of ~1.3 mm/year. Total displacement has so far reached about 30,000'. The Tetons are also home to a single remaining glacier, seen here on the left side nestled between the three large peaks.
#mygtnp #GrandTetonNPS #Geology #FindYourPark #tetonglacier #tetonfault #mygrandteton

Fluorescent minerals at the Dice Museum, Calvin College. Fluorescence occurs when ultraviolet light, which is invisible to the human eye, strikes a mineral, is absorbed, and then the light is remitted as visible light. Visible light, such as the green and orange colors seen in these specimens, has much longer wavelengths than ultraviolet light. The minerals themselves are emitting this light, it is not reflected light; this difference is what gives them a glowing appearance.
#minerals #geology #dicemuseum #fluorescence #postmorerocks #onmondayswepostminerals

Selenite gypsum at the Dice Museum, Calvin College. Specimen is from Chihuahua, Mexico. The clarity of these is well demonstrated by the back lighting.
#OnMondaysWePostMinerals #PostMoreRocks #MineralMonday #geologyrocks

Somebody said it was #InternationalRockDay but all the posts under the hash tag are 🤘 & 🎸. Here's a gorgeous garnet mica schist from the Dice Museum. Specimen from Wrangell Island, Alaska.
#PostMoreRocks #GeologyRocks #🤘

It's Friday!!! This #FridayFold is from the Bighorn Mountains of Wyoming, where highly deformed Archean gneisses are exposed. These rocks are the roots of an ancient mountain belt, formed when the N. American continent was still in it's infancy. Blocks of crust of different ages collided with one another through tectonic movements if the Earth's lithosphere, and slowly accreted together.
#PostMoreRocks #Geology #BighornMountains

Close-up shot of bedding-cleavage relationship in Wilhite slate, part of the Proterozoic Walden Creek Group in the Western Blue Ridge.
There are two distinct planes throughout these rocks - the more shallow dipping one is the bedding, which is the original layering formed when these rocks were originally laid down as sedimentary units. That surface is now folded back and forth, although this is not seen in this photo. Here I focused on a single limb of the fold. The second planar surface is the cleavage - this plane is not folded. This penetrative fabric formed due to compressive tectonic stress much later, during the first phase of mountain building in the Southern Appalachians. It is related to the folding, oriented like a bisecting plane in the center of the folds. Geostudents - which direction is the hinge of the anticline, and are these rocks upright or overturned?
A day early and a bit indirect for this week's #FridayFold. ☺️ #GeologicStructure #BlueRidge #PostMoreRocks #scienceeducation #tectonics

The serpent's head. #FridayFold
Last week I shared a photo of one of the "tails" of the dragon, a "famous roadcut" up in the Grenville of Ontario, CA. This is the head of the beast. The black layers are amphibolite rock that has been "mixed in" with a pinkish-gray granitic gneiss. The whole area was caught up in a shear zone, which is like a fault but much deeper in the Earth's crust, where rocks become subject to ductile processes of deformation, bending instead of breaking. The amphibolite is like a spaghetti noodle getting wound up on a spinning fork, folded back and forth over itself many, many times. At this time, the Grenville Mountains had formed, a chain of thickened crust that would have rivaled the modern day Himalayas. These rocks were somewhere on the order of 30 km deep at that time, so the Grenville Terrane of Eastern Canada gives geologists a look into what the deep parts of mountain belts are like.
#geologyrocks #tectonics #grenvilleprovince #ohrocks #postmorerocks #heretherebedragons #GeologicStructure

This week's #waterfallwednesday flows in from Great Smoky Mountains National Park. •••••
Thanks to @profcarriganonu for the geology of GSMNP. ・・・
The subject of this photo is the Great Smoky Thrust Fault, the most significant fault in the Southern Appalachian Mountains. Strongly cleaved Neoproterozoic phyllites lie on top of the Ordovician Knox limestone. This is an Alleghanian structure, active during the Late Carboniferous to early Permian, when Africa and N. America collided to form the supercontinent Pangea at the end of the Paleozoic Era. Here, in Great Smoky Mountain National Park, the fault is visible behind a small waterfall at White Oak Sink, where a small creek falls over the contact and enters a cave in the limestone below. This photo was taken a few years ago; this area is now restricted to human activity in order to protect the Smoky Mountain bat populations from the disease called White Nose Syndrome. This photo was also selected as the Earth Science Picture of the Day in May, 2014.
#greatsmokymountains #friendsofthesmokies #GSMNP #WhiteNoseSyndrome #WhiteOakSink #thrustfault #geology #waterfallsfordays #nature_waterfalls #longexposure_shots #southernappalachians #postmorerocks
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#nationalparkgeek

The subject of this photo is the Great Smoky Thrust Fault, the most significant fault in the Southern Appalachian Mountains. Strongly cleaved Neoproterozoic phyllites lie on top of the Ordovician Knox limestone. This is an Alleghanian structure, active during the Late Carboniferous to early Permian, when Africa and N. America collided to form the supercontinent Pangea at the end of the Paleozoic Era. Here, in Great Smoky Mountain National Park, the fault is visible behind a small waterfall at White Oak Sink, where a small creek falls over the contact and enters a cave in the limestone below. This photo was taken a few years ago; this area is now restricted to human activity in order to protect the Smoky Mountain bat populations from the disease called White Nose Syndrome. This photo was also selected as the Earth Science Picture of the Day in May, 2014.
#greatsmokymountains #friendsofthesmokies #GSMNP #WhiteNoseSyndrome #WhiteOakSink #thrustfault #geology #waterfallsfordays #nature_waterfalls #longexposure_shots #southernappalachians #postmorerocks

Mina Sauk Falls, just off of Taum Sauk Mtn and a short hike down from the MO high point. The water falls over the 1.5 Ga Precambrian rhyolites that dominate the bedrock of this region.
#geologyrocks #waterfalls #longexposure #minasaukfalls #taumsaukmountain #MOStateParks #rhyolite #geologyfieldtrip #waterfallsfordays

Folded banded-iron formation at Dice Museum.
Banded iron formation begin as sedimentary rocks formed in the ancient oceans. They consist of layers of iron oxide minerals and quartz. Their formations are related to the build up of oxygen in Earth's atmosphere in the ancient past by the earliest photosynthetic organisms. Later, the rock was buried, metamorphosed by heat and pressure, and deformed into this folded structure. This beautifully cut and polished specimen is on display at the Dice Mineral Museum at Calvin College. The back lighting allows the red and yellow colors to done vibrantly.
#FridayFold #DiceMuseum #bandedironformation #geology #PostMoreRocks

Finally got around to cataloging my new pieces and figured I'd share! Starting from the left:

1)Scleractinian Coral from Virginia Beach, Va (Also the first fossil I've ever found!)
2) Phyllite (metallic rock in the center), produced through low to medium grade metamorphism of Slate, found near James River State Park, Va.
3) Red quartzite, also found near James River State Park, Va.
4) Mudstone from Ireland!
Note: Only the coral sample was collected by me! Thank you @juliekolleene @kcurl89 and @lindzatkins for thinking of me and picking these up 😁

#Geology #PostMoreRocks

Potholes at Johnson Shut-Ins in the East Fork Black River.
Potholes always have small stones in them, which are swirled around during high water flow and grind out the circular hole.
#geology #PostMoreRocks #potholes #johnsonshutins #MOStateParks #missouristateparks #geomorphology #andariverrunsthroughit

A trio of geos on Elephant Rocks.
Last week I took my petrology class to SE MO to the St. Francois Mtns. to see the igneous rocks - mostly alkalic granites and rhyolites, and diabase dikes. I love my job teaching these future scientists. Although the weather was crummy, we still got to see some great stuff. Then on Saturday evening we held a retirement dinner for one of my colleagues who is finally hanging up the old rock hammer after 50 years!! Got to honor his legacy, and then enjoyed catching up with some old alums who had made the trip back to campus. All in all, being a professor isn't bad if you can stand all the committee meetings! 😂😂😂 #geology #StFrancoisMountains #elephantrocks #science #nature #STEMCareers

⬅swipe to see full panorama➡
A group of former students at the boulder field in Johnson Shut-Ins State Park, MO. These boulders were washed down during the catastrophic collapse of the Taum Sauk Reservoir in 2005. 1.3 billion gallons of water in 12 minutes can move some big rocks!! #MOStateParks
#missouristateparks
#boulderfield #johnsonshutins #geology #PostMoreRocks #postmoreportraits

#Repost @profcarriganonu with @repostapp
・・・
Diabase intrusion in Granite
Here are two igneous rocks, a dark, mafic diabase cutting through a gray-pink granite. This is located near the Silvermine Dam in SE Missouri, among the St. Francois Mountains. The dike, cutting through the granite, is obviously younger; radiometric ages point toward a difference between them of roughly 120 million years.
#Igneous #Geology #PostMoreRocks #Science #Nature #MagmaMonday #MountainMonday 

Tension Cracks on a Folded Layer

When rocks are deformed at shallow levels in the Earth's crust, they experience a mix of brittle and ductile processes. As a strong, competent layer is compressed and bends, the outer part of the hinge area can crack. Imagine compressing a long, thin piece of wood from both ends and the board begins to split at the hinge. Here a layer of stone is loaded with tension cracks along the outer arc of the fold. Many of the cracks taper downward to the inner part of the fold and disappear. The outer arc of the layer has to stretch during the folding process, while the inner arc is compressed. This causes stretching on one side and squeezing on the other, and can produce extensional features like these tension cracks. Some of the cracks here appear to be filled with later vein material, precipitated from water. When a layer of rock is buckled in this manner, the strain is concentrated in the hinge, and the rock layer remains largely undeformed in the limbs of the fold. This is the opposite from what happens in some other folding processes, but that's for another time.
#FridayFold #Geology #GeologicStructure #Science #Nature #PostMoreRocks 

Bedrock-Constricted River
As the East Fork Black River enters Johnson Shut-Ins, the bedrock changes to a much more resistant layer, and the stream transitions from broad, sandy meanders to a narrow, rough channel in rock. The stream splits into many small segments. Small falls, potholes, and pools dominate. In SE MO, this kind of feature is referred to as a shut-in, where the bed of the river is constricted down to a narrow channel due to a change in the bedrock.
#Geology #Shut-Ins #StatePark #Geomorphology #Rivers #PostMoreRocks #Waterfalls #WaterfallWednesday #longexposure 

Bedrock-Constricted River
As the East Fork Black River enters Johnson Shut-Ins, the bedrock changes to a much more resistant layer, and the stream transitions from broad, sandy meanders to a narrow, rough channel in rock. The stream splits into many small segments. Small falls, potholes, and pools dominate. In SE MO, this kind of feature is referred to as a shut-in, where the bed of the river is constricted down to a narrow channel due to a change in the bedrock.
#Geology #Shut-Ins #StatePark #Geomorphology #Rivers #PostMoreRocks #Waterfalls #WaterfallWednesday #longexposure #waterfallsfordays #nature_waterfalls

Cool Contact.
Chilled margin in granite, St. Francis Mtns.
When hot magmas intrude into older, cold rocks, they freeze fairly quickly on their margins. As a result, they are finer-grained right next to the contact, and coarser-grained inside this thin rind. Here a pink-white-gray granite (lower left) intruded a greenish gray rhyolite (upper right) and developed this texture quite nicely. The minerals in the granite such as K-feldspar (pink), plagioclase (white), and biotite (black) are all much smaller in size at the contact with the old volcanic rock. This feature is called a chilled margin, and it allows us to determine which rock of the two is the youngest, and which is the oldest. In this case, the granite is younger and the rhyolite is older. By using clues such as these, geologists put rocks in a sequence and determine their relative histories.
#MagmaMonday #Igneous #StFrancoisMountains #granite #rhyolite #geologyrocks 

Fossil Meteorite with Cephalopod at the Field Museum
Most of the meteorites we have to study fell out of the sky in the not too distant past. Meteorites that feel a lot time ago, geologically speaking, are really rare. That doesn't mean that rocks from space haven't fallen to Earth throughout its history, of course; in fact old meteorite impact sites are well known in the rock record. Big meteorites often vaporize on impact, and small ones weather away quite easily at Earth's surface. There are a few, however, that 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 with the alien rock encased in another stone. 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, which happened to also get fossilized very near the meteorite.
#Geology #Paleontology #Meteorites #FieldMuseum #Science #Nature #PostMoreRocks

Limestone/dolomite in Croatia! (I'm the little human at the bottom btw). Red staining like this indicates that these rocks were iron-rich and oxidized over time as rainfall percolated through (limestone is naturally very porous). Because of the iron molecules involved, the staining left behind is rusty in color. #Geology #Geomorphology #PostMoreRocks

GIANT Topaz, Dice Museum

I had the privilege of visiting Calvin College last week in Grand Rapids, MI, to serve as an external reviewer for their Geology Program. While I was there I was able to visit the Dice Mineral Museum, which is absolutely gorgeous. They were given an incredible collection of specimens of minerals and some stunning fossils also. I'll post more photos in the coming days. Here's a GIANT Topaz crystal from Brazil (it is about 6" tall). The clarity of this piece speaks to its chemical purity, as topaz often takes on other colors due to inclusion of small amounts of foreign ions. Topaz is prized as a gemstone, and is also very hard, defining H = 8 on the Mohs hardness scale.
#OnMondaysWePostMinerals #DiceMuseum #CalvinCollege #Geology #Topaz 

#FridayFold for today is pink Baraboo quartzite. These are the first folded rocks I ever saw up close in person as an undergraduate student years ago and it blew my mind.
#Geology #Science #Nature #Metamorphic

A small overflow of water streaming down the rocks at Woodall Shoals. This exposure of bedrock is one of the best in the eastern Blue Ridge. There are 7 fold generations here, and numerous other geologic features. And the scenery ain't bad either.
#geology #woodallshoals #waterfall #longexposure #chatoogariver #waterfallsfordays #nature_waterfalls

#FridayFold: Shell Canyon Monocline

Rocks in the foreground are horizontal, at the edge of the hill they are vertical, and at the top of the hill farther in the distance they are horizontal again.
Coming down out of the Bighorn Mountains heading west on Hwy 14 is a fantastic drive through the Shell Canyon monocline. The fold here is in the third dimension.
#GeologyRocks #geologyfieldtrip #ScienceEducation #GeoPhotography #PostMoreRocks 

Rainbow Falls, Hawaii
This is an old photo from a number of years ago, but despite its lesser qualities I like the cave carved into the lower rocks by weathering and erosions, while the more resistant layer above allows the waterfall to persist. Located near Hilo on the Big Island on the Wailuku river.
#waterfalls #geology #hawaii #waterfallwednesday #erosion #rainbowfalls 

#FridayFold : High-grade Bighorn metamorphics
Today's squishy rocks come from Powder River Pass, the high point on the southern route over the Bighorn Mountains. These are metamorphic rocks that were buried deep in Earth's crust, the deep roots of ancient mountains. These gneisses are roughly 3.0 billion years old. #Geology #ScienceEducation #PowderRiverPass #Metamorphic #GeologicStructure 

More Yellowstone Volcanics: Deformed Obsidian at Lewis Falls
Obsidian is a volcanic rock made entirely of glass. The lava cools so quickly that minerals don't have time to form. However, the cooling process takes some time, so it continues to flow as it is cooling. During that process, the hot, nearly solid material, can fold under the stress that builds up from the process of flowing.
#Geology #Science #Nature #YellowstoneNPS #MagmaMonday 

Dead Indian Monocline
#FridayFold This drape fold marks a Laramide uplift to the west (right in the photo) on the eastern side of Yellowstone National Park. The Clarks Fork Yellowstone River flows out here to the NE.
#GeologicStructure #Geology #YellowstoneNPS #FindYourPark #OptOutside #choosemountains

It's Not Quartz in this Yellowstone Volcanic Rock
One of the features that is often used to distinguish quartz from feldspars is that quartz is often colorless and clear. Feldspars, on the other hand, are opaque and white, pink, gray, or other colors. These features tend to be true, but they aren't always.
That's why when I'm in Yellowstone, I take my students to see this particular volcanic rock. It's located just off of Grand Loop Dr., about 3+ miles past Gibbon Falls. At this point you've driven down into the caldera and the steep cliff on the right is made of this rhyolite tuff. The first guess is often "quartz", because it bears a lot of resemblance to it being clear and colorless, but closer inspection indicates that it is the wrong shape. Many of the grains look fairly square or rectangular, and none of them have the classic hexagonal barrel shape of quartz. Instead, this is a feldspar as the shape suggests, but it is a high-temperature variety called sanidine. Sanidine is only preserved in volcanic rocks, so many students simply haven't seen it up close unless their mineralogy/volcanology/petrology courses purposefully include it in a lab activity.
#MagmaMonday #MineralMonday #Igneous #Volcanic #Science #Geology 

Yellowstone's Yellow Stone

This volcanic rock is present in the valley walls of the Grand Canyon of the Yellowstone. It's a nice rhyolite with flattened vesicles - the oval-shaped holes that are present throughout it are former gas bubbles in the magma, that were then flattened after the magma was erupted and deposited on the surface.
#Geology #ScienceEducation #STEM #NPS100 #FindYourPark #MagmaMonday #Igneous 

Today's #FridayFold comes from the Grenville Province of Ontario, CA, at Egan Chutes Provincial Park. The Grenville Province is a large area of Precambrian (Middle Proterozoic, ~1.2-1.0 Ga) metamorphic rocks that are the deep roots of an ancient mountain belt, long eroded away. Toonie and maple leaves for scale.

#Geology #GeologicStructure #Tectonics #Science #Nature 

The crew enjoying the basalt columns from last summer's field camp at Sheepeater cliff, Yellowstone NP.
#magmamonday #geology #YellowstoneNPS #nationalparkgeek

Well time to get back to sharing pictures of rocks in this new year, eh? Smile folks, here's today's #FridayFold !
This funny looking rock comes from the high-temperature metamorphic rocks of the western Blue Ridge, Southern Appalachians. This is along a road cut near Hayesville, NC. These rocks started out as sedimentary, sandstones, but were buried deep by tectonic collision and heated until they started to melt. The white layers among the gray are the material that had melted out, but it cooled and solidified again before the whole package was brought back up to the surface.
#GeologyRocks #GeologicStructure #metamorphic #blueridge #southernappalachians

Minerals on Monday: Large Hornblende Crystals from Greenmantle Farm
Here's a crystal shape that any student of minerals should learn to recognize easily. Amphiboles are one of the main groups of rock-forming minerals, with tens of species of various chemical compositions. The main long edges form a rhombus with ~60/120 angles, which is then cut by two short sides on the ends. Each half of the crystal resembles the bottom of a letter "A", for Amphibole. This group is from Greenmantle Farm near Wilberforce, ON.
#mineralmonday #mineralscience #mineralogy #geology #crystals 

#FossilFriday - a small vertebrate bone weathering out of the rock at Badlands Natl Park. Any paleontologists out there who can tell us more about this specimen? It was found very close to the teeth that I posted a week ago.
#fossils #badlandsnps #paleontology #geology #fieldcamp

#FridayFold: "Z" Fold in Grenville Marble
The Grenville Province is a large area, mostly in Ontario, where billion year old igneous and metamorphic rocks are exposed. These rocks are the roots of an ancient mountain belt, that at the time would have rivaled today's Himalaya. They are long since eroded away. Those mountains formed as two continental masses collided, and in that process many of the rocks were faulted and folded. Here is one small isoclinal Z-fold (meaning the limbs on each side have the same orientation). Structural geology students: since the top of the Z points to the left but the beds are tilted to the right, what does this mean for larger structures that might exist in the area?
#FridayFold #metamorphic #EarthCaching #geologicstructure #marble #Grenville 

#FridayFold : Parasitic Fold in Minnekahta Limestone, Black Hills
On the NE flank of the Black Hills dome lies the Whitewood anticline, a fairly large fold structure. Near the nose of that much larger fold, my students and I found this much smaller fold that mimics it. The axis of this fold has a similar orientation as the larger structure, and both of these are quite similar to the northern regional structure of the Black Hills dome. Small folds that are similar to much larger structures are called parasitic folds by geologists, and they help us unravel complexities of large structures that can't always be easily seen due to their immense size.
This fold is in the Permian-age Minnekahta Limestone, an algal stromatolite-rich micrite - meaning it is made of lime mud, was deposited ~250-300 Ma, and has original structures in it that were made by algae in a tidal environment.
Geostudents, how else would you describe this fold?
#GeologicStructure #BlackHills #GeologyRocks #ScienceEducation 

Cascade Canyon Conclusion
I wrapped up a series last week on many different boulders found along Cascade Canyon trail in Grand Teton National Park. Each one is unique and tells a story about the processes of magmatism, deformation, and metamorphism in the continental crust. Together, they give a small window into the processes that shaped the Wyoming Craton, a large block of Archean crust that forms the basement in this part of North America. I'll eventually get around to posting these all on my website as a blog post. Here's a pretty picture of the canyon.
#GeologyRocks #GrandTetons #NPS100 #CascadeCanyon #postmorerocks #mountainmonday #nationalparkgeek #choosemountains #tetoncollective

Granite Intruding Granite

In this fifth installment of Grand Teton rocks from Cascade Canyon we have two igneous rocks, a fairly fine-grained granite and a very coarse-grained one. This means that one of these rocks intruded and cut through the other. One was solid while the other was still cutting through as liquid magma. The contact between them is quite sharp, which indicates that the older rock was fairly cold when the younger intruded. As to which one is the older and which is the intruder, the more coarse-grained rock gives a clue. Right at the margin of the contact, near my Leatherman tool, there are some crystals that appear to be growing out of the contact. This could be a coincidence, but it probably isn't. The grains in the more coarse-grained rock also get quite a bit larger away from the contact. These two observations are consistent with the coarser grained rock intruding as the magma, coming into contact with the older, colder rock, and first forming smaller crystals that grow out from the contact where the magma is cooling most quickly, then growing larger crystals just a few inches away as those early formed crystals provide a buffer for the heat transfer, allowing it to cool more slowly and grow larger crystals.
My observations and interpretations here could be wrong. In order to test this model, I would want to spend much more time inspecting the rocks for more clues, and obtain samples to look at under the microscope. And to really get a firm grip on the ages of these rocks geologists will date them using minerals that contain radioactive isotopes. Science moves forward by this process of observation, interpretation, and continued testing of models and hypotheses. A good scientist always asks him or herself "what if this idea is wrong?", and finds a way to check.
#GrandTetons #CascadeCanyon #GeologyRocks #Granite #NPS100 #mygtnp #FindYourPark #OptOutside

Cascade Canyon #4: Deformed Partial Melts

The 4th installment in the current series on the boulder field from Cascade Canyon in the Grand Tetons is this hot mess. This is another example of a mixed rock including both metamorphic and igneous materials. The white layers were melts that had formed when metamorphic rocks were heated enough to begin the melting process. They migrated into this black-gray rock and there they solidified and deformed. Substantial folding can be seen as you trace the layers around. These processes occur deep in the continental crust at high pressures and temperatures over a protracted period of time.
#CascadeCanyon #GeologyRocks #niceGneiss #geologicstructure #GrandTetonNationalPark #NPS100 #FindYourPark #mygtnp

Migmatite Fold
The first rock from that Teton boulder field I mentioned in my previous post is this high-grade metamorphic rock with a beautifully folded layer in the center. The white sections were liquid melts migrating through the gray metamorphic rock at depth in the Earth's crust. Eventually, they solidified as igneous rock, some of which were then later themselves metamorphosed during continued tectonic activity. The white layers have notable black rims where the melts were chemically reacting with the solid gray gneiss as they passed through. A rock like this, where there are both metamorphic and igneous rock types mixed together, is called a migmatite. The larger folded layer in the center is especially interesting, since there are other layers around it that are not deformed. There are likely multiple episodes of melting interspersed with deformation and various stages of high pressure and temperature metamorphism.
#GrandTetons #FridayFold #CascadeCanyon #nicegneiss #NPS100 #FindYourPark #WCSS2016 #mygtnp

#FridayFold : Boulder at Greenough Lake Campground, MT

This beautiful boulder adorned our campsite up in Montana, down in the Rock Creek valley of the Beartooth Mountains, just after coming down from Beartooth Pass on Hwy 212. It's a beautiful gneiss with spectacular close to isoclinal folding, no doubt part of the very old Archean gneisses of the Wyoming Province.
Enjoy your weekend everyone!
#BeartoothMountains #nicegneiss #GeologyRocks #GeologicStructure #leathermanforscale #postmorerocks 

Close fold in Precambrian gneiss at Grand Teton National Park, part of the Archean Wyoming craton. Found this one along the Cascade Canyon trail. Happy Friday everyone!
#FridayFold #NPS100 #postmorerocks #GeologicStructure #gneiss #leathermanforscale #WCSS2016 #mygtnp

Devils Tower phonolite with orthoclase phenocrysts.
This is a close up on the igneous rock that makes up Devils Tower, a rock type that geologists call a phonolite. Much of the rock is a very fine-grained gray matrix of minerals, which indicates that it cooled from magma quickly so the crystals didn't have time to grow. A good number of the lighter gray to white grains here, however, are plenty large enough to see easily. Those grains are larger, so they had more time to grow. Since they had more time to grow, they must have started growing earlier than the matrix, and the magma must have been cooling more slowly. Since the magma was cooling slowly, it must have been at greater depth in the Earth's crust. They are the mineral orthoclase, a potassium-rich feldspar, one of the most common minerals in Earth's crust. Geologists call larger minerals in a fine-grained volcanic matrix phenocrysts, meaning "visible crystals". This texture indicates the magma went through 1) a slow cooling stage where the orthoclase crystals were growing, and 2) a fast cooling stage when the rest of the matrix grew. Stage 2 was likely associated with the emplacement of the magma into the place it now occupies, since it wouldn't move any more once solid. Stage 1 would have occurred when the magma was deeper in the crust. This magma crystallized to solid rock about 40 million years ago.
#devilstowernps #igneous #geologyfieldtrip #WCSS2016 #magmamonday

The sedimentary rocks surrounding Devils Tower are a big reason for why the place is so beautiful. They add wonderful red and yellow colors to the blue of the sky and the green of the vegetation and the grayish white of the tower itself. The oldest layer at the bottom is the red Triassic Spearfish formation. Above that are a couple of layers of Jurassic rocks, including the white thin layers of the Gypsum Springs Fm., an evaporite deposit. My favorite of these however is the yellow Hulett sandstone at the top (also Jurassic). While the Spearfish was deposited in an arid environment, the Hulett sands were deposited in shallow water near the shore of an ancient beach on the coast of the Sundance Sea. Ripple marks are common on its bedding planes as waves rolled back and forth. At that time, the magma that would form Devils Tower hadn't yet melted out of the deep crust, and wouldn't arrive on the scene for another hundred million years or more.
#devilstowernps #geologyrocks #WCSS2016 #findyourpark #nps100 #goparks

Clastic Dike at Pinnacles Overlook, Badlands NP.
One of the more unusual geologic features that can be found at Badlands Natl. Park is called a clastic dike. These are rocks made of sand, silt, and clay, but they do not lie horizontal like most sedimentary layers. Instead they cut through other layers, often vertically like this one here. They begin as flat layers of sediment, deposited here in the Badlands by ancient streams. As more sediments are deposited, the pile gets thicker and these layers are buried and compressed. During burial, water that was in between sand grains gets squeezed out as the mineral grains get compressed closer together. As this happens the layers increase in density. However, due to differences in materials, some layers lose their water more slowly and remain a less dense, water-rich mush. The pressure from the layers above continues to increase, to the point where our water-rich layer of sediment is now gravitationally buoyant due to its lower density. All it takes now is a crack to form, and this material can squirt up, filling the space and forming the vertical layer of sediment called a clastic dike.

#badlandsnationalpark #geologyfieldtrip #fieldcamp #clasticdike #geophotography

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