Aerial Geomorphology #3: Minnesota River Valley and Glacial River Warren

Onto Aerial Geomorph #3, although a similar flight along the MRV in the future will result in an Aerial Geology post - there is some very interesting geology within the valley (very old rocks).

This flight's purpose was to check out the Minnesota River and Minnesota River Valley just southwest of the Twin Cities. Like the Mississippi River, this river has an interesting glacial and geomorphic history. Also, this is one of those specific topics early on in my geology education that got me hooked.

Although this flight was to explore the Minnesota River, it was really a story of Glacial River Warren. The Minnesota River is an under fit stream, which means it occupies a valley that is too large for it. The Minnesota River Valley was carved out previously by the much-larger Glacial River Warren. A nice explanation with figures can be found here, but to summarize, the glacial river was fed by the draining of Glacial Lake Agassiz at the end of the most recent glaciation (just about 10,000 years ago). This enormous discharge of water removed a lot of overlying sediment and rock and in some parts of the valley some very old rocks are exposed (see Morton Gneiss, Montevideo Gneiss, Sioux Quartzite, and so on).

A friend of mine came along since she'd never been in a small plane before. Most of the following pictures are courtesy of her. We took off from Flying Cloud Airport in the trusty Cessna 152, flew southwest along the Minnesota River, stopped quickly at Le Seuer Airport, then flew back to Flying Cloud.

The Geo-plane.

Flight path (red line) for MRV Flight #1, starts at Flying Cloud Airport (KFCM), southwest along the Minnesota River to Le Sueur Airport (12Y), then back to Flying Cloud.

Flight path (red line) along the valley between where it turns northward and the Twin Cities.

The first glimpse into the size of this huge former river became apparent near the city of Jordan, Minnesota.




Northwest aerial view of Jordan, Minnesota, with US Highway 169 on the bottom left, and Minnesota River on the other side of the city.

Aerial view of a textbook version of an oxbow lake in the Minnesota River, upstream from Jordan. A gravel pit is in the background, just on the other side of the oxbow.

Although it wasn't clearly apparent, using Google Earth allowed for a great way to illustrate how the Minnesota River compares to the current valley, and a look into how both rivers have affected the building of cities and roads. Below is a cross-section made using Google Earth (and some stratigraphic information) across the above photograph of Jordan.

Geologic cross-section near Jordan, Minnesota.

The Minnesota River Valley near Jordan is about 3 miles across. The city of Jordan and US Highway 169 are built upon a fluvial terrace (former flood plains which are now above the current flood plain). These terraces, while providing convenient flat ground to construct roads and cities, are also remnants from glacial activity causing stream rejuvination. The Jordan Sandstone outcrops near Jordan, named so after the city (rock formations are typically named after the location which they were best described, called a type locality). The current Minnesota River is very small in relation to the valley it occupies. The Glacial River Warren occupied the entire valley during its existence. The glacial sediment thickens toward the northwest, while the stream itself is at nearly bedrock-level. Numerous gravel pits occupy the highland on the north side of the river, mining aggregates (sand and gravel) deposited from glacial activity. Needless to say, it is one of Minnesota's main natural resources. In 1997, over $180,000,000 worth of aggregate was mined in Minnesota (MnDOT). 

Upstream from here provided another good view of the Valley near Henderson, Minnesota. This was a good spot to really visualize the size of River Warren.

Northwest aerial view up the Minnesota River Valley near Henderson, Minnesota (left edge of photograph). The Minnesota River flows from bottom left to upper right, turning around a bend and going northeast. The valley is distinguished by the tree cover, and the highlands are cropland or fields.

  

Cross-section across the Minnesota River Valley by Henderson, Minnesota (see photo above). The valley is about 3 miles wide at this point. Henderson appears to be built upon a small terrace, with another smaller terrace uphill from it.

Cross-section of Minnesota River Valley near Henderson, Minnesota, showing the size of Glacial River Warren (defined by the width of the valley) to the current Minnesota River.

Masterful artistic rendering of what the Glacial River Warren may have looked like to Early Holocene pilots flying around Henderson, Minnesota.

The above illustration is what I had envisioned in my mind during the flight. Parts of the Amazon River get this wide.

Content I had seen what I wanted to see, we proceeded to return back home. Since it was such a nice day for flying, we took plenty of additional pictures.

Aerial view of Le Sueur, Minnesota, along the Minnesota River.

Landing at Le Sueur Airport.

Aerial view of meanders, meander cut-offs, and point-bars along the Minnesota River.
From the air is a good place to see and learn fluvial geomorphology.

I see some LWD

Aerial view of the Minnesota River. Even though you learn about point bars forming on the insides of river bends, I'm still amazed that the textbooks are right. 

Prior Lake, a good geographic marker to contact air traffic control.

View of Minneapolis in the distance



Crazy Pilot

Crazy Copilot

Good day for some aerial geology! And I got brownies!

Aerial Geology #1: First Contact

At last, I've used my powers of flight to make a geologic observation from the air. This is an exciting first to my blog, and I look forward to more of the same.

This last weekend I flew down to a Fly-in/Drive-in breakfast and air show that is held every summer in Winona, Minnesota. For the few years I worked, went to school, and learned to fly there, I would volunteer for this event and it was always a thrill. I've missed the last two, on account of being in Missouri for grad school, so it was great to be able to fly there from the Cities. Also, it was nice to get in some cross-country flight time. I took the trusty Cessna 152 I've been hopping around in lately.

My trusty steed, 100x stronger than the average horse

I learned to fly along the Mississippi River, so it was great to re-visit my roosting grounds. And of course, you can't beat the view.

Composite photograph of view from the Cessna 152 flying up the Mississippi River;

stream valleys (left view), Mississippi River and Highway 61 (forward view), and Lock and Dam #5 (right view) 

Now, for the geology. On the way back to the Cities I noticed a decent sized quarry down amongst the little stream valleys.

Now, I've seen quarries from the air before, but after looking closer (especially in the photograph), I noticed something obvious: there were two distinct formations in that outcrop; an orange lower unit and a buff-gray upper unit.

Outcrop near Winona, Minnesota, showing Cambrian-Ordovician boundary as the sharp contact between the Jordan Sandstone (orange, lower unit) and Oneota Dolomite (gray, upper unit)

I think any other place and I would have just dismissed it, but that combination of rock colors in that sequence, and for this region, represents a geologic contact that is well-known to every geologist and geology student in the area. The bottom orange-tinged unit is the Jordan Sandstone, and the upper gray unit is the Oneota Dolomite. The contact is the Cambrian-Ordovician unconformity.

Stratigraphy of Minnesota

All geology students recognize the Jordan Sandstone because it tends to break easily and stains your hands and clothes a rusty-orange. There is a large outcrop of rock that students are brought to which we just call "Homer", and the Jordan Sandstone is part of the sequence of rocks exposed there.

Roadside geology at Homer Ridge; me (left), fellow geologist Laura, and Jordan Sandstone (right)

The Oneota Dolomite, above the Jordan Sandstone, is known around the area for making up the resistant caprocks for the bluffs. Around Winona everyone sees this formation all the time as Sugar Loaf, the pinnacle of rock seen from almost anywhere in the city, even at night (they light it up), as a remnant from quarrying.

Sugar Loaf bluff, Winona, Minnesota

Aerial Geomorphology #2: Twin Cities Flight

After moving to the Twin Cities I recently began flying out of Anoka County-Blaine and Flying Cloud Municipal airports. I had my biennial flight review in a Cessna 172, and also got checked out in a Cessna 152, which was a bit of a change for me, since almost all my single engine time is in a Piper Warrior II. The one advantage of the Cessna 172 and 152 is the high-wing design allows for better downward visibility, and therefore, better aerial photography. In the spirit of my blog, I took a friend up flying the other day, both because she had never gone flying in a small plane before, and also to get some nice pictures of local geomorphology.

The plane

The pilot

The photographer

The plan of the flight was to take off from Anoka and fly east towards the St. Croix River and back while checking out the many lakes and streams along the way.

 

Flight planning

This route took us over lots of the smaller lakes, and it seemed like everyone with a boat had it out that day. It had been really warm lately, so I don't blame them.

Center City, Minnesota

South Center Lake (bottom half), North Center Lake (top half), and Little Lake (far back, right)

http://goo.gl/maps/7COV

After flying around my friend looked down and said, "Hey, meandering stream!". This turned out to be the Sunrise River, and it meadered quite a bit, even had some cutoff meander bends. Aerial geomorph gold! We followed it for a while as it flowed into some larger pools which became streams again.

Sunrise River, complete with meander cutoff bends

http://goo.gl/maps/dfbs

Sunrise River, with good examples of meander cutoff bends

http://goo.gl/maps/dfbs

Sunrise River, Sunrise River Pool #1 (left), Mud Lake (background)

http://goo.gl/maps/iu5h

The Sunrise River flowed into the Pool, where it branched and part of it went southward and another part of it went westward. We followed the westward branch, which eventually flowed into Martin Lake. All along the way the river had lots of meander cutoffs.

Sunrise River flowing into Martin Lake

http://goo.gl/maps/F2wr

It's nice to be flying again, and after years of geology education I love to notice the interesting landforms and stream types. Time to plan some other flights! 

Megafault review

Usually 2 A.M. is my bed-time but when I see something called "Megafault" playing on the Syfy channel, well, sleep will have to wait. The following are my observations of hilarious quotes and situations as they happen in this cinematic masterpiece starring Brittany Murphy as the heroine seismologist.

(Brittany puts an aluminum case on the ground) "This is a tri-axial seismometer, it measures changes in the ground". While this is a ridiculous statement, on second thought it's fairly realistic. After being asked a hundred times what I'm doing when performing geophysical surveys I tend to say things like that.

(observing growing fault from helicopter) "The earthquake is still moving!"

‎(observing growing fault from helicopter) "Look! That's at least a 7.0 on the Richter scale"


Apparently earthquakes make helicopters shake. While they are in the air.


They constantly interchange the terms "fault" and "earthquake".


"The worst is over...for now". Sooo then the worst isn't over?


"It's possible this fault could continue to rupture indefinitely and tear apart the United States!"


"Air traffic control in the midwest has been wiped out"...."that means every airplane in the midwest is now flying BLIND".....(cuts to to military cargo jet, flying through patly cloudy skies) "Indianapolis ATC, we need a visual, we're flying blind!" (jet starts to nose dive, then runs into another plane, I think, apparently lack of ATC causes parts of your plane to explode at random).

"I don't just blow things up" right after he blows up a port-a-john as a distraction so they can steal a helicopter.

(Scene of cargo jet crash) Father and daughter, with only slightly dirty faces, walk away from the burning wreck.

(To military-guy) "What are you going to do, declare war on an earthquake?"

(Military guy explaining a secret satellite) "This tectonic-weapon fires a laser at the earth's surface and re-crystallizes the water table" I can't even remember this whole quote, he said a lot and it was so horrible that I can't even piece it back together.

(After deciding to use the tectonic-weapon) "Sir, after this works you'll need to fly me home"...."M'am, if this doesn't work you won't have a home to fly to"

(Semi-truck driving wildly, dodging nothing, across a dirt road as random explosions occur around it)....Passenger, "We have to stop!"....Driver, "No way, we have an earthquake on our tail!"

Semi-truck passenger crawls across side of truck, while it is moving, with random earthquake-explosions all around, in order to disconnect the trailer, which is loaded with petroleum. They can't stop or the earthquake will catch up with them.

"So, that's the epicenter of the fault?"

"Can the USGS confirm your megafault hypothesis?"

"What we plan to do is trigger a second earthquake to rob energy from the main one"

"After diverting the earthquake, the Grand Canyon will absorb all its power"

(They detect an RV with airborne radar) "What, ground traffic? This airspace is supposed to be clear!"

"P-waves at zero percent!"

"Sir, the tectonic weapon has destabilized the mantle!"...."Mantle? What mantle?"

People randomly start catching on fire around Yellowstone because of the 'destabilized mantle'

"The earthquake is headed towards the Yellowstone Caldera! Do you know what that means??"...."Hey, man, she doesn't care, she just wants to get home to her family"

"Now the earthquake is moving north. It's like lighting a fuse thats big enough to blow up the entire planet"

"We can't move the Grand Canyon"...."Why not?" They then discuss a plan to build a new Grand Canyon with some explosives.

(Brittany nervously eyes a few crates in the back of the Osprey as they fly west) "Are you sure we have enough explosives to build a trench the size of the Grand Canyon?"...."Yes, this should be enough"

"Sir, the quake has entered Vail!" (the earthquake now manifests itself as a snow avalanche even though there are no mountains nearby with much snow. The town is wiped out)

"We've installed an infared sensor on the triggering mechanism." This line is all by itself. It has no context or explanation.

"What's wrong?".....(Brittany, suddenly quiet, senses something) - "The quake is hitting Denver". They are in Wyoming.

"At the end of the day, all you have are two things: your family, and the choices you make."

Brass Compass

I recently graduated with my master's degree in geology and as a bit of a graduation present one of my good friends, who is also a graduate student, gave me a little treasure he had obtained while overseas in the Army. This present is a brass compass, very similar to a Brunton.

The compass part of it still works great, and the dip-bubble works, although the leveling bubble is off-center, but I don't mind. The thing is more of a classy desk piece than a field tool (although I'd still use it). I believe it's made of brass because it's a good deal heavier than a regular Brunton compass. The pictures don't do it justice, it shines like a slightly tarnished penny.

Although the giver of this gift didn't know it, this meant a lot to me for a specific reason. At my undergraduate geology program they would award a gift to two graduating students based on their performance. They can choose between a Brunton Compass or a GPS. I chose the GPS because I'm really into the whole GIS/GPS thing, but the field geologist looks back sometimes and wonders why I didn't choose the compass. Receiving this antique showpiece brass compass has gone a long way of curing that, on top of the fact that it is a wonderful desk piece and conversation starter that has traveled across the world and given to me by a good friend.

"They will beat their swords into plowshares..."

While on a recent week-long geology trip through Oklahoma, Texas, and New Mexico, my group had the pleasure of being given a small tour of an interesting little project near Carlsbad, New Mexico. We were driving through some of the dusty backroads around the brine pits and oil rigs to the east of Carlsbad when we reached a dead end with a concrete marker and plaque.

The marker read:

"The first nuclear detonation in the Plowshare Program to develop peaceful uses for nuclear explosives was conducted below this spot at a depth of 1,216 feet in a stratum of rock salt. The explosive, equivalent to 3,100 tons of TNT, was detonated at the end of a horizontal passage leading from a vertical shaft located 1,116 feet southwest of this point. Among the many objectives was the production and recovery of useful radioactive isotopes, the study of heat recovery, the conduct of neutron physics experiments, and the provision of a seismic source for geophysical studies."

Below the spot we were deciding to have lunch for the day, a nuclear device was detonated on December 10, 1961. This detonation was called Project Gnome, part of Operation Plowshare, a program to use nuclear explosions for peaceful projects. We were told by our guide that the distinction between a "nuclear weapon" and "nuclear device" is the intent in which it is used (basically as a weapon or not). This location was chosen because of the very thick salt layers in the subsurface which are known for essentially repairing themselves (since the salt flows somewhat), making salt domes and rocks good for storing harmful materials.

Other than the fact that we were essentially standing about 1000 feet from where a nuclear explosion occurred, my favorite part was the name of the project, "Plowshare Program" or "Operation Plowshare", named so after a verse from Micah 4:3...

"And he shall judge among the nations, and shall rebuke many people: and they shall beat their swords into plowshares, and their spears into pruning hooks: nation shall not lift up sword against nation, neither shall they learn war any more"

The concept of "swords into plowshares", or turning weapons into peaceful tools, seemed very fitting for the project.

While we were touring the site, we were informed that a very small amount of radiation leaked from one of the wells after the detonation, but didn't cause any harm or contaminate any other sites. No radiation has leaked since then, and the area is protected from drilling. This was shown to us to illustrate the potential success of the nearby Waste Isolation Pilot Plant, which stores harmful materials underground (basically, if a nuclear explosion could be contained in the salt rocks, then a harmful chemical storage facility should have no problems).

After returning home and reading more about the project it seemed there was much more negativity towards the explosions, and it seemed as if the radiation leak was taken more seriously by the public than the scientific community. Our guide fully supported the Gnome detonation, but on the internet it seemed it had much more negative publicity by the non-scientific community. But I suppose that's how these things tend to be. The guide was extremely knowledgeable about not only this project but almost any geological question we asked him, which biases me towards his judgement.

Accretionary Wedge 43: My favorite geologic illustration

In response to the Accretionary Wedge #43 hosted by In the Company of Plants and Rocks:

Although I have many geologic illustrations which I would like to show, the one which has the most meaningfulness to me is the geologic cross-section of Minnesota from the Minnesota Geological Survey.

http://www.mngs.umn.edu/Minnesota%20Geology%20Images/images/geologic%20terrane%20cross%20section%20Minnesota%20geology_jpg.jpg

As far as cross-sections go, there isn't much here which couldn't be seen in other parts of the world. The reason this means so much to me is because it started the process which "awakened" me to the world of geology. In my third year of undergraduate studies (while declared as a physics major but not really into it) I decided to take the Introductory Geology and Geology of Minnesota classes, both taught by the same professor. The beginning of both classes was the same: basics on rock types, geologic processes, etc. But even still, all those concepts were things that happened "somewhere else". Geology was still something that happened in some mountain somewhere else on earth.

This cross-section was eventually shown to us (probably the first geologic cross-section I had ever seen. The idea of a cross-section was so foreign to me, how could we possibly "see" underground like that?). It was displayed by itself on the screen for a good while as the professor talked. This illustration declared, "Geology is closer than you think, it's right beneath you, all around you, is not all the same and tells a fascinating story". Even Minnesota, a state I always considered to be rather boring (flat farmland or flat forest), was interesting underground. The school I went to was down in the Paleozoic sediments, but eventually I would see all the other parts of the state, with evidence of the Midcontinent Rift, the St. Cloud granites, and so forth. It was diagrams of local geology like this one which got me so interested in geology in the first place.