New to the GIS map: Aeromagnetic & Gravity Anomaly map layers highlighting the Midcontinent Rift (among other things).

Recently, two layers were added to the Wisco Geology GIS map:

•  Aeromagnetic: This map layer is a composite made from aeromagnetic surveys in Wisconsin.  Maps like this are used for mineral exploration.  Source: USGS and others.

• Bouguer Gravity Anomaly: This map layer shows where variations in gravity occur due to changes in rock type, density or thickness.  Source: USGS and others.

The most striking feature of both layers--but especially the gravity anomaly map layer--is the swath of red color in western Wisconsin extending into Minnesota and Iowa. This area was flooded by huge amounts of lava about a billion years ago as the continent started to split and pull apart. Today, this is called the "Midcontinent Rift". The lava cooled to form basalt within the rift zone.  The basalt here could be many miles thick and it is generally more dense than the surrounding rock types. For these reasons, the gravity anomaly map layer shows the rift as an intense "gravity high" zone.

Aeromagnetic and gravity surveys became more extensive in the 1940s as remote sensing technologies were developed. Before this time, the existence of the Midcontinent Rift was not known. Geologists were aware of igneous rock outcrops including basalt at places like Big Manitou Falls and at the Dalles of the St. Croix River / Interstate Park, but the full extent and cause of these igneous rock formations were not understood until the 1960s when plate tectonics became more well understood and geologic mapping became more complete across the globe.

The Midcontinent Rift system shut down before the continent was torn completely apart.  If rifting had continued here, the geology of this area might have resembled the Great Rift Valley of Africa and would have eventually filled with sea water to form something like the Red Sea. You can see that Lake Superior sits within the rift zone. Most people believe the Great Lakes were formed by glaciers, and is largely true, but the underlying rift influenced the formation of Lake Superior. You can read more about it in this article by geologist Dr. John C. Green of the University of Minnesota-Duluth.

Click here to check out the Wisconsin Geology GIS map.  Once in, turn on the Aeromagnetic and Gravity Anomaly layers (these are both near the bottom of the layer list to the right of the map).

Note:  I georeferenced existing maps to add these to the Wisco geology app. If you study geology, you have probably seen these maps before.  What's interesting about viewing these in the Wisconsin Geology GIS app is that as overlays, you can view these in context with the other map layers such as outcrops.

Meet up with a 2.8 billion year old from Wisconsin

Looking to meet up with a 2.8 billion year old?

We found your match.

Your can turn the GIS app into an online dating site (albeit for seniors) by doing the following:

1.  Click here to open the Wisconsin Geology GIS map
2. Click the  "Filter" button near the upper right of the map, then toggle on the "Age Dated" filter. 

 

 

The mapped outcrops will then show only those that have been dated.  Click on those outcrops for a profile of each.

The oldest rock outcrops in Wisconsin are found in the central part of the state.  Just east of Marshfield, a gneiss outcrop has been dated around 2800 - 3000 million years old by a geologist named W. Randall Van Schmus.  Randy gets around and has dated a LOT of rocks around the country.

You'll see several outcrops dated by Van Schmus along the Black River in Clark and Jackson Counties, specifically near the Arbutus Dam.   You'll find rock outcrops older than 2000 million (2 billion) years old along the Wisconsin River in Wood and Portage Counties as well.  These are of course mapped on the Wisconsin Geology GIS app.  Love begins here (opens the GIS map).

Extraterrestrial Impact Craters in Wisconsin

Incoming asteroid!   This nightmare scenario has inspired plenty of bad movies, but the reality of these events is supported by lots of good science. It has happened many times before:  Indeed, Earth is whacked by space rocks from time to time, and the big chunks have significantly impacted the planet while making an abrupt stop here.

The Earth Impact Database lists 190 confirmed impact structures on Earth.  Two of these are located in Wisconsin, and of course the Wisconsin Geology GIS app has them mapped! Read on to find out more about each, and where to look for the geological version of ET.

The "Rock Elm Disturbance"
An asteroid perhaps 600 feet in diameter smacked into what is now eastern Pierce County Wisconsin somewhere between 450 and 500 million years ago, piercing through hundreds of feet of bedrock and leaving a crater nearly 4 miles in diameter in its wake.  The crater has been nearly erased over time by geological deposition and erosion. It is still faintly discernible on the Wisconsin Geology GIS map:  Click here to zoom to the location of the crater,  then study the "hillshade" effect closely.  See it?  Look in the area that is today between County Road CC on the west, County Road HH on the south, County Road S on the east, and 570th Ave on the north. Within a roughly circular area, the drainage pattern is different within the crater than it is in the surrounding area. Drainage and erosion appear to have been influenced by the underlying crater. Some geologists believe this impact was just one of many that rocked the Earth during the Middle Ordovician Period. Several other possible impact craters of perhaps the same age are being studied in Oklahoma, Iowa, and in Lake Superior.

On the GIS map, a red X marks the approximate center of the impact structure (the central uplift) and there is an orange outcrop identified on the south rim where today the Rock Elm and Plum Creeks exit the impacted area.

Cross section of the rock strata in the area of the Rock Elm Disturbance.
Brown, B.A. WGNHS Survey Map 88-7

Topographic relief map of the Rock Elm impact site. Click to enlarge.

The Rock Elm Disturbance was first recognized in the 1940s by geological mapping of the bedrock of western Wisconsin.  Right in the midst of generally horizontal sedimentary strata, something had clearly 'disturbed' the rock layers in this area (hence the name) although at the time it was unclear to stratigraphers and other geologists just what exactly caused this unique geology.

Over the years, the existence of impact structures became more widely recognized in science.  Stratigraphers were not the only geologists involved in identifying impacts like this one.  Minerologists also got into the game.  For example, a mineral called reidite was found in the Rock Elm crater.  Reidite forms under very high pressure and has been found in nature in only 4 other locations on Earth, all within other known impact structures.   Gold, which is also sometimes associated with impact events, has been found in the beds of the streams flowing south out of the Rock Elm crater.  Gold, you say?  If I just distracted you with shiny golden objects, check out a blog article about gold panning in this area---yes, there is public land in and near the impact site.  Here is a very good video by Dr. William Cordua, a geologist who has studied this impact structure in detail. Additional references are linked below, and you can bring up more by doing a Google search on the "Rock Elm Disturbance".  The story is shaping up to be better than any Hollywood movie.
Update:  See also this interactive GIS map:   https://geologyinsight.maps.arcgis.com/apps/webappviewer/index.html?id=09ed828f4c8340419f4c93eb2aa447bd

Glover Bluff
Another impact structure is located in northwestern Marquette County Wisconsin (click here to view the location on the Wisconsin Geology GIS map).  This crater is between 1 and 5 miles in diameter. It is more difficult to recognize on the surface because it is mostly buried under the thick moraines of Wisconsinan glaciation. Quarrying activity has uncovered enough evidence of an impact to make this a 'confirmed' crater.  Fractured bedrock (including shatter cones) and impact breccia surround a central uplift, all telltale signs of a significant extraterrestrial impact. If you visit the area, please keep in mind this area is mostly private land--don't trespass!  Bruce Willis didn't save this area from the asteroid, and he won't save you from the wrath of the locals, either.

Meteoric fall
Smaller chunks--meteors--punch through the atmosphere and land without forming a crater. Once firmly planted on Earth, the meteors become meteorites. Lots of folks run around looking for meteorites--they are valuable and can be sold for more than a few hundred quids.  When Earth-born rocks are mistaken for meteorites, geologists have a solemn duty to inform the stone bearer of the meteorwrong.  There have been some famous meteorite discoveries in Wisconsin, however.  Near West Bend in Washington County, several metallic meteorites have been found--the largest pieces weighed over 400 pounds!  These so-called "Trenton Meteorites" are rather famous among the meteorite hunters.  A meteorite found near Algoma in 1887 is today located in the University of Wisconsin Geology Museum.

Go to the Wisconsin Geology GIS app for more.  Remember you can search the map:  Search terms like "meteor" or "crater" to bring you to known locations of such objects in Wisconsin.

References:

• Earth Impact Database (website), Planetary and Space Science Centre
  University of New Brunswick
• The Rock Elm Disturbance (web page),  Wisconsin Geological & Natural History Survey
• Rare Mineral Found in a Wisconsin Crater, Astrobiology Magazine, 2015
• Trenton Meteorites, Mindat.org

Gold in them thar Wisconsin hills?

I'll strike up a conversation about geology with anyone who is interested.  Often, this conversation turns to gold.  Literally.  When people think "geology" they often want to talk about the most malleable metallic mineral.

Wisconsin is not known for it's gold mines.  Unlike the San Francisco 49ers, our football team's gold color is more reflective of cheese than of the metal.

Yet, one could  point to places in Wisconsin and say indeed, there is  gold in them thar hills!

How much gold, you ask?  Well, one mine in Rusk County Wisconsin produced 334,000 ounces of gold in 5 years (1993 - 1997), not to mention 3.3 million ounces of silver, plus copper to boot.  Reading this, you might be licking your pickaxe while singing "Silver and Gold" along with Yukon Cornelius while you book a trip to Wisco.

But wait, there's more.  Significant gold deposits have  been reported in Ashland and Marathon Counties as well.  Some deposits have names:  There is the "Northern Belle Mine" and the "Chicago Mine" between Drummond and Mellen in northern Wisconsin;  The "Reef Deposit" east of Wausau;  and the "Lynn Deposit" in Oneida County.    Of course, the gold in these deposits is not easily recovered.  These are "massive sulfide" deposits that would require expensive recovery operations.  Not to mention, the permitting process would be a nightmare and you'd face opposition from groups concerned about potential water pollution from this type of mine.  Want an example?  All of this is currently playing out with the "Back Forty" gold/copper mine just across Wisconsin's border in the U.P. of Michigan.

OK, so maybe you don't want to mine for gold using new-fangled technology or deal with modern-day politics, you just want to find gold the old-fashioned way: Panning.  There is hope.  Yes, you can pan for gold in Wisconsin and you might even find a little (just don't give up your day job and be sure to follow the rules).  One of the best sites to pan for gold in Wisconsin is at  Nugget Lake Park along Plum Creek in Pierce County.  The gold here may be associated with an impact crater known as the "Rock Elm Disturbance" formed during the Middle Ordovician Period somewhere between 430 and 455 million years ago. More on this crater in future blog posts.  Let's get back to the gold! 

So where does "X mark the spot"?  Right here on this blog, you'll find a treasure map:  Find gold on the Wisconsin Geology GIS web map by clicking here and then typing "Gold" into the search box in the upper left of the map.  You'll see a list of results; Clicking each result will bring you to the location in Wisconsin where gold may be found, including the examples given above.  Further, you have technology the old-timers could have only dreamed of:  The mapped locations include a popup with a link and Google Map directions.  Using our very own app, your smart phone will lead you right to paydirt!  You will be richly rewarded, though probably not in gold or other monetary form--your reward will most likely come from experiencing Wisconsin's great outdoors.  All that glitters is gold....in the form of Wisconsin's 15,000 sun-splashed lakes or the many other brilliant rocks and minerals you can find here. That's gold, Jerry!  Gold!

References:

• Wisconsin Department of Natural Resources (WiDNR), "Reclaimed Flambeau Mine" (web page) 
• Oneida County web site, the Lynn Deposit (web page).
• Aquila Resources, "Back Forty" mine web site 
• Wisconsin Geological & Natural History Survey (WGNHS) web site, minerals > gold page.

The Wisconsin Geology GIS app: Pretty maps, useful functions.

A geology professor of mine used to like to describe things as "aesthetically pleasing".  A goal of this project is to map geology in an aesthetically-pleasing way, and also a technically-useful way.

For example, I'm using the Wisconsin Geology GIS map to explore the "Eau Pleine Shear Zone" between Wausau and Stevens Point where the Archean Marshfield Terrane fused with the Superior Craton around 1850 million years ago*.  Awesome!  I need to explore this further!

Zooming in to this area on the GIS app,  I turn on aerial imagery which underlies the LiDAR-based topographic hillshade on the mapping app.  In less than a minute, I have a pretty cool looking 3D-ish map of my area of interest.

Further, I see the Wisco Geology GIS app shows outcrop locations marked with Xs.  Some of the outcrops within the shear zone are on public land (Mead Wildlife area).  I might have to check these out in person.  Time for a road trip?   I can find out easily enough:  Click an outcrop location: Within the popup for each is a "Directions To" link.  Tapping this will pop open a Google map giving me driving time & directions to my chosen outcrop.  I can load up the Wisco Geology app on my smart phone so the nice Google voice will guide me right to the outcrop(s) so I can keep my eyes on the road and my hands upon the wheel.

Wait, so Google Maps provides directions to rock outcrops?  Yep!  At least, as integrated in the Wisco Geology app, Google will serve as a guide to outcrops just like it helps find brew pubs. 

The next time I'm in the Wausau Area, I plan to visit these outcrops (and perhaps the Red Eye Brewing Company as well).

Click here to open the Wisconsin Geology GIS map to the area I've described in this post. It's just west of I-39 south of Mosinee near Dancy.  Try these tips out yourself for this area, or any other area of interest in Wisconsin.

*By the way, I plan to have more information about the Eau Pleine Shear Zone, plate tectonics, and the Marshfield Terrane in future blog posts. I may also update you on the Red Eye brews.

New! Click anywhere on the GIS map to view a summary of geologic features

The problem with geology maps you've seen before

Most geology maps have lots of colors and symbols representing various geologic units---too many, perhaps: Onlookers are constantly referring to the map legend, then back to the area of interest, legend, map, and back and forth your eyes go. 

Further, if you want to know something about surface versus bedrock geology, you have the added complication of using different maps altogether.  Most likely these "old school" paper-based maps are of different scales and areas of extent and it's hard to get a "big picture" view of the geology of an area.  Not to mention, the big paper maps are hard to use in the field -- especially a windy field.

This geology mapping project aims to be different.  Here's how:

Now you can just click on pretty much any location on the Wisconsin Geology online GIS map to open a popup showing a summary of geologic features for the spot clicked.

Here are three ways to access geology information from the Wisconsin Geology GIS map:

1. See a landform that looks interesting on the Wisco Geology GIS map?  Pick it and click it, and a popup will provide a summary of geologic information (bedrock and surficial) for that area.  Super interesting geology will eventually have links from the popup to a blog article.
2. Don't want to click and poke at the map so much?  Just press the "Info Summary" button in the top ribbon, then just zoom to an area of interest. Within your map view extent, you'll see a summary of geologic features along with any outcrops that might be in sight. These descriptions will update automatically as you pan or zoom around the map.  Nifty, huh? 
3. You know you can use the Wisconsin Geology GIS map on a smart phone, right?  Yep, you'll have gobs of geologic information at your fingertips while out in the field -- and the little blue dot knows where you are at all times, of course. While hiking, just tap the map to see what's around--and under--you.

This will take a while to compile

I'll have to compile information from dozens and dozens of geology maps and convert them into my specific GIS format to make this all work. It'll take a while.  As geologist J. David Love has said, "You can't do geology in a hurry."

This project overall is still in it's infancy, but since few people are even looking at this project, I thought I'd go ahead and publish this even as it's incomplete and I'm still testing this idea.

Areas that are completed with more refined, large-scale geologic map data summaries as of September 25, 2018 include the counties of:

• Brown
• Door
• Kewaunee
• Sheboygan

I suggest you try out the above counties first (look in the Green Bay area).

You can look at other parts of the state, but the summary information is based on a very generalized small scale maps and lacks detail. The polygons and boundaries are purposely transparent. If you are able to see polygon edges, please do not interpret them to be precise locations of geologic contacts.

In the near future, I will be compiling more detailed bedrock and surficial geology into this "summary" layer for the following areas:

• The Fox Valley area of Eastern Wisconsin
• Southeastern Wisconsin
• Northeastern Wisconsin
• Central Wisconsin including Marathon, Portage, and Wood Counties

Stay tuned!

GIS map updates coming soon

A user of the Wisconsin Geology GIS app made a great suggestion:  Differentiate the outcrop symbols by type (rocks, landforms, etc).  Most of the outcrop symbols represent bedrock outcrops, but I originally did have some marking the locations of glacial landforms (the moulin kames in western Sheboygan County for example) and other interesting sites as well.

In the future, the X symbols on the GIS map will represent bedrock outcrops only.  In case you read this: Thanks for the suggestion, Paul!

I'll be making the LiDAR-based hillshaded landforms "clickable" with popup information.  The hillshade effect already does a nice job of highlighting landforms, but I'd like to take it a step further and offer some interpretive information to help people identify them as drumlins, former lake plains, and so forth.   I think this will be pretty cool.

Stay tuned!

How to access citations / references

As I collect information for this Wisconsin Geology project, I am making every effort to ensure the work of others is being properly cited.  You will find source materials with the names of the authors located:

• As attributes of mapped features on the Interactive GIS map
• On the "References" page accessible as a tab on this blog (above)
• As references within the blog articles themselves

Thanks to all of the geologist who have done the hard work to make this project possible!  Special thanks to the Wisconsin Geological & Natural History Survey (WGNHS) and the United States Geological Survey (USGS ) for making so much information publicly available through their web site.

How this Wisconsin Geology project was born

This Wisconsin Geology project started as my effort to use GIS to map the rock outcrops that I have visited (or hope to visit). I wanted to attach basic information about each site so that it's all with me as I travel around my home state of Wisconsin. I also wanted to capture photos and notes about each site that I visit.  Further, I wanted to be able to access the unique perspective offered by LiDAR terrain maps to help interpret the geology of any given area.

That's how this GIS map came to be.

It was originally intended for my own use, but I decided to share it with you and create this companion blog because I thought you might find it interesting too.

When you open the GIS map and begin to zoom in and play with it, you'll see:

GIS app on a smart phone

• Outcrop locations mapped with a red or orange X.   When tapped on, these outcrops will bring up descriptions and/or photos or short articles about the outcrop.  Thousands of additional outcrops are mapped with a black X (visible when zoomed in) but the black ones will not have as much attached information as those colored red or orange.

• Landforms illustrated with a "hillshade" effect. There is a medium-resolution hillshade for the entire state (source: Wisconsin SCO) and this is displayed at the intermediate map scales.  When zoomed in to large scales, some areas (about half of the state so far) have an even more detailed hillshade that was produced from county LiDAR projects. The hillshade / topographic relief layers make landforms "pop out" and they help illustrate Wisconsin's wonderful glacial landscapes. 

• Lithology and stratigraphy:  Well and other borehole locations are represented as black dots. When clicked, these points will bring up information about subsurface lithostratigraphy (click the Related Tables link on the popup to view formation and rock type information with depth of each layer).  This GIS app includes about 35,000 of these locations.  The data source is the Wisconsin Geological and Natural History Survey (WGNHS) "WiscLith" database dated January 2018.

• Property lines show up when zoomed in (large scale).  You can click on each property to see the land owner (helpful for field trips!). This information is from the Wisconsin Statewide Parcel Map project.  The base map also switches to an aerial photo at large scale. 

• Other map layers that further illustrate various aspects of Wisconsin's geography and geology are listed to the right of the map (click on the checkbox to make them visible--some are only visible at appropriate map scales).    You can also read more about the GIS app on it's description page. 

If you haven't done so already, go to the GIS map (click here) and start exploring!  Zoom to a place you are interested in (be that your home, your favorite park, etc) and learn more about the fascinating geology and natural history that belies the surface.

I intend to do much more with this project in the future.  Stay tuned!

Special note:
A great deal of information for this project comes from the WGNHS and I am grateful they make so much of it available.

How to get started

Take a look at this interactive GIS map (click here) and zoom in (Tip: your mouse wheel works great for that).

Wondering how to use it?  For starts:

Look for locations marked with a red or orange X.  Tap on them and see what pops up.  As of today, almost 300 of these locations are mapped across Wisconsin, marking interesting geologic outcrops or formations. If you're in Wisconsin or planning a visit, look for formations near you and tap on them.

Playing with the map in this manner is a great way to introduce yourself to this project and to Wisconsin's geology.

The popups include a summary, description, and significance. Not sure what some of the terms mean? No worries, future blog posts will help.  Interested in visiting any of these sites yourself?  Click the link to get driving/hiking directions on your smart phone.

Geology is like augmented reality for the planet

An excellent article in Wired by Marcia Bjornerud,  professor of geology at Lawrence University:

https://www.wired.com/story/geology-is-like-augmented-reality-for-the-planet/

An excerpt:
"As I hope my students will learn, though, looking at the planet through a geologic lens is something like strapping on an augmented-reality headset. It invites you, from your vantage point in the present, to summon up Earth’s deep past and far future—to see these parallel worlds with your own eyes, like digital overlays."

Welcome! A first post on why this blog exists, what it's about, who it's for, and where it's going.

Hi there and welcome!  I feel the need to write a short introduction before digging deeper into Wisconsin's geology.

Why did I create this blog?

I've had a lifelong fascination with Earth history, but I don't want to simply read about it -- I love to go  outdoors to see, touch, smell, and taste the Earth around me to see the evidence myself.  Also,  I like to map and document what I have seen, or hope to see in the future, and to try piece the evidence of the Earth's story together on my own.

And I happen to be living in Wisconsin.

Hence, this blog. And this app.

What's your reason for reading this? 

Most people are intrinsically interested about the Earth. As children, we examined rocks and wondered why they look the way they do.  Some are pretty. Some have interesting shapes.  Perhaps we visited state or national parks -- these are most always located near natural or geologic wonder.

As kids, we were given introductory lessons in Earth Science in school. Possibly, if we had a good teacher who really understood the subject and made it interesting, we learned something fascinating about the Earth.   Or, perhaps those early lessons didn't sink in.  Maybe we were distracted by other things (by adolescence, everyone is!).  Maybe we remained enthusiastic about Earth science, but by high school it just "wasn't cool" enough or "profitable enough" to take your studies in it further. 

Or perhaps you followed your passion for Earth science and became a geologist or related professional. Great!  I hope you continue reading too.  This project may not be for the professional geologist, but I hope even you find it useful.

Where is this going? 

I'm going to use this blog (and it's companion GIS mapping app) to dig deeper into Wisconsin's deep past.  My goal is to learn a lot myself as we go.   I hold a degree in this subject matter and I read as much as I can about it; However, I don't hold a PhD and I am not necessarily an expert in all of the topics this blog will explore.

 I hope you use this blog and the GIS mapping app as a guide to explore on your own.  If you are in Wisconsin, be sure to go outdoors!  I'll wrap up this post with one of my favorite quotes on geology:

"The best geologist is the one who has seen the most rocks".  Herbert Harold Read.