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).

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!

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.