Sign in to follow this  
Followers 0
ByronForestPreserve

Question about "unique feature" requirement.

10 posts in this topic

I live in a town in Illinois that happens to have the only surface outcrop of Cambrian rocks in the state (and therefore the oldest rocks found at the surface in the state). The rocks were raised almost 300' in an earthquake in the late Paleozoic and follow a now inactive fault line. However, it's a very small area (1.5 miles long by about 600' wide) and the most visible rocks are in an old quarry on private property; it wouldn't work by itself as an Earthcache. Still, I want to find a way to put this together into an Earthcache, and did some reading. I know that Earthcaches can contain multiple sites, but I'm not sure what I'm thinking of would be considered a "unique feature."

 

Here's what I came up with: At the start of a trail, they are walking over Ordovician deposits (Galena Stage, 454-446 mya). Heading down this trail, they will descend to an earlier Stage (Platteville, 455-454 mya) and then to Ancell Stage deposits (459-455 mya). Where the trail ends near a river, they will be standing on the uplifted Cambrian deposits (497-492 mya). At the water's edge are glacial outwash deposits from the Wisconsin Episode (25,000 years ago). The trail is clearly marked and well maintained. Obviously I need a task for cachers to accomplish...I could ask either for the elevation change or for them to match rock types with ages from their observations (as in: photos of limestone, sandstone, siltstone/shale, and glacial pebbles, and ask them which they observed at stops along the route). Someone with time on their hands would probably be able to figure that out without visiting, though.

 

Will that work? Is almost 500 million years of rocks from three geologic Periods in one short (quarter mile) hike a "unique feature?" Is there a better task you could think of for people to do?

 

My other option would be to just have a single waypoint where the youngest and oldest deposits in the state meet--and the only place in the entire state where that happens (glacial outwash lies over the edge of the Cambrian rocks). It's definitely unique! The best task there, though, would be a photo, and I see that the Earthcache site asks that photos be optional. That specific area doesn't have any cuts into the Cambrian rock except for a small creek, so answering questions about the rock itself might be difficult.

 

Any thoughts and suggestions are welcome, and thanks for any help!

0

Share this post


Link to post

Personally, I would probably try and develop the first option, and see if there were a way to make the write ups unique enough to submit them as individual Listings, rather than a series of stops in one Listing.

 

I tend to avoid Logging Requirements that can be easily figured out from maps and such, like your elevation example. Describing the rocks, or giving a series of pictures describing various rock types and asking people to identify the correct rock type would be a bit better. Nothing is fool proof, and a determined cheater will likely find a way to game the system.

 

Sounds like an interesting project. Good luck!

0

Share this post


Link to post

I have definitely looked at descriptions for Earthcaches that seem to be along these lines.

 

Off the top of my head, here's an example of one that features a place where you can see the transition from Canadian Shield to St. Lawrence Lowlands. The task is a bit basic but it is neat to see the transition:

 

https://www.geocaching.com/geocache/GC1TV9W_the-frontenac-axis

 

I think you have the ingredients to do something really interesting. To add a bit of meat to the tasks, you could ask them to answer more detailed questions about the qualities of the rocks they are seeing. Are there fossils in the Ordovician deposits? I have seen a couple of Earthcaches that show a photo of a fossil, and then have the cacher find and measure that specific fossil.

0

Share this post


Link to post

When EarthCache.org set up the new requirements for EarthCaches, they made providing "an earth science lesson" the number one requirement. A unique feature by itself is not usually enough to become an EarthCache - how it formed or why it's unique might be an acceptable lesson.

Setting up tasks for the cachers to do while providing this lesson has always been, for me, the hardest part of creating EarthCaches. A science teacher friend told me to do this: determine what lesson you are trying to impart, then think of tasks that lead the cachers to the knowledge you wish them to gain.

So, what lesson are you trying to give the cachers?

Is it the fact that there are rocks from three Periods visible here? Anywhere you have contact between strata of two older Periods, you can usually find some Recent deposits nearby, giving you three Periods, so this doesn't sound unique in itself. Yes, your glacial deposits on top of a very old stratum are more interesting than the usual, but what is the "lesson" there? You might be able to talk about the dynamic earth, and how new deposits are continuously being made through the rock cycle. ("Out with the old and in with the new!" is how I saw the cycle described once.)

 

From your description of the trail, there are probably many other opportunities to give a lesson:

- Are any of the strata inclined from horizontal, and are all at the same angle? Can this be tied to the uplift? Earthquakes and glaciers both affect topography.

- Is there any weathering of the older rocks, giving sharp, angular debris in a talus slope? Can this be compared to the roundness of the glacial debris?

- Are the rocks of different types, like marine, terrestrial, lacustrine, riparian, etc.? You now have a lesson on climate change over a long period of time(including the Ice Age.)

 

Take your time, make several visits, look at both the details and at the big picture - somewhere in there you will come up with at least one lesson, and maybe more!!

0

Share this post


Link to post

I think I like the trail idea. You can have them ID differences in the rocks, both in appearance and in how they have weathered, perhaps.

 

Then again, I'm a sucker for weathering questions, probably because I feel like I finally understand it to some level.

0

Share this post


Link to post

Personally, I would probably try and develop the first option, and see if there were a way to make the write ups unique enough to submit them as individual Listings, rather than a series of stops in one Listing.

 

I tend to avoid Logging Requirements that can be easily figured out from maps and such, like your elevation example. Describing the rocks, or giving a series of pictures describing various rock types and asking people to identify the correct rock type would be a bit better. Nothing is fool proof, and a determined cheater will likely find a way to game the system.

 

Sounds like an interesting project. Good luck!

 

I don't think the individual layers are necessarily Earthcache-worthy; the Ordovician limestone and St. Peter Sandstone cover the entire north central part of the state, and there's one Earthcache for the St. Peter Sandstone south of my location. Or rather, that trail isn't the best place to see the rock layers as there's a lot of vegetation. I would be more tempted to get our maintenance guys to make the small inactive quarry on our forest preserve property more accessible and do a lesson about marine deposits and limestone vs. dolomite vs. chert because the different colors of rocks are really obvious. But yes, that's what I had in mind for the task--to describe the rock types with photos and have them match that to rocks along the trail. Thanks!

 

I have definitely looked at descriptions for Earthcaches that seem to be along these lines.

 

Off the top of my head, here's an example of one that features a place where you can see the transition from Canadian Shield to St. Lawrence Lowlands. The task is a bit basic but it is neat to see the transition:

 

https://www.geocaching.com/geocache/GC1TV9W_the-frontenac-axis

 

I think you have the ingredients to do something really interesting. To add a bit of meat to the tasks, you could ask them to answer more detailed questions about the qualities of the rocks they are seeing. Are there fossils in the Ordovician deposits? I have seen a couple of Earthcaches that show a photo of a fossil, and then have the cacher find and measure that specific fossil.

 

The trail has a lot of vegetation, but there are enough outcrops on the way down that they should be able to tell the limestone from the sandstone from the Cambrian. There are better locations in the area for fossils, and I see myself doing a few Earthcaches in the near future--we are hoping to create a Geotour on our properties, and I can think of three or four potential Earthcache sites, including one for Ordovician fossils. There aren't many Earthcaches nearby...one close to my house, and the next closest 35 miles away. In fact, running a quick search I don't see any EC's within 100 miles that ask anyone to find fossils. Well, I guess I should make one. :D That aside, thanks for the link and the suggestions...having some detail in the tasks would be good. There are places they can see the quartz sand crumbling from the sandstone, and at least one nice outcrop of limestone that shows the color difference between plain limestone and dolomite. Thanks!

0

Share this post


Link to post

When EarthCache.org set up the new requirements for EarthCaches, they made providing "an earth science lesson" the number one requirement. A unique feature by itself is not usually enough to become an EarthCache - how it formed or why it's unique might be an acceptable lesson.

Setting up tasks for the cachers to do while providing this lesson has always been, for me, the hardest part of creating EarthCaches. A science teacher friend told me to do this: determine what lesson you are trying to impart, then think of tasks that lead the cachers to the knowledge you wish them to gain.

So, what lesson are you trying to give the cachers?

Is it the fact that there are rocks from three Periods visible here? Anywhere you have contact between strata of two older Periods, you can usually find some Recent deposits nearby, giving you three Periods, so this doesn't sound unique in itself. Yes, your glacial deposits on top of a very old stratum are more interesting than the usual, but what is the "lesson" there? You might be able to talk about the dynamic earth, and how new deposits are continuously being made through the rock cycle. ("Out with the old and in with the new!" is how I saw the cycle described once.)

 

From your description of the trail, there are probably many other opportunities to give a lesson:

- Are any of the strata inclined from horizontal, and are all at the same angle? Can this be tied to the uplift? Earthquakes and glaciers both affect topography.

- Is there any weathering of the older rocks, giving sharp, angular debris in a talus slope? Can this be compared to the roundness of the glacial debris?

- Are the rocks of different types, like marine, terrestrial, lacustrine, riparian, etc.? You now have a lesson on climate change over a long period of time(including the Ice Age.)

 

Take your time, make several visits, look at both the details and at the big picture - somewhere in there you will come up with at least one lesson, and maybe more!!

Those are good questions to consider. The Ordovician rocks cover quite a few counties, and the Cambrian rock by itself, though unique in the state, isn't quite exposed enough at that site to create a good task. That's why I thought the juxtaposition of those layers would be the interesting part, though it's truly the Cambrian layer that makes that particular spot really fascinating.

 

What started this whole thing was reading some old state geological survey publications about my town. They used to take field trips to see the Sandwich fault, which was visible in a rock cut along a railroad. I went to the spot and unfortunately it's too crumbled and has too much undergrowth to see the faults along the cut anymore. Then I stopped at the old quarry of Cambrian rocks, which were used to build the dam in town, but even if I had landowner permission, there's nothing to see but some mossy rocks now. The site at the state park puts both of those together, since it's the fault's location that resulted in the Cambrian rocks being uplifted to the surface. So, while that was my initial interest, I think the focus will be on how this short hike is the only place in the state where they can see these deposits together. There's also an unconformity, but I think that might be more than I need to include. Maybe. Probably.

 

I will definitely be getting out there again soon. I've done that hike several times as I have a regular geocache along the trail, but I haven't looked specifically with an Earthcache in mind. I'm sure I can make it work. Thanks!

0

Share this post


Link to post

I think I like the trail idea. You can have them ID differences in the rocks, both in appearance and in how they have weathered, perhaps.

 

Then again, I'm a sucker for weathering questions, probably because I feel like I finally understand it to some level.

 

Mannnn, I hear you. I have been reading everything I can find lately to get a better handle on the geologic history of my immediate area. Every time I hike over a hill or mound I try to figure out if it's weathered limestone, crushed and re-positioned limestone from the Illinois glacier, Canadian Shield till from the Illinois glacier, or outwash along the river valley from the Wisconsin glacier. I want the state geologist on my speed dial.

0

Share this post


Link to post

I think I like the trail idea. You can have them ID differences in the rocks, both in appearance and in how they have weathered, perhaps.

 

Then again, I'm a sucker for weathering questions, probably because I feel like I finally understand it to some level.

 

Mannnn, I hear you. I have been reading everything I can find lately to get a better handle on the geologic history of my immediate area. Every time I hike over a hill or mound I try to figure out if it's weathered limestone, crushed and re-positioned limestone from the Illinois glacier, Canadian Shield till from the Illinois glacier, or outwash along the river valley from the Wisconsin glacier. I want the state geologist on my speed dial.

Keep in mind that geologists, like other scientists, must often publish to live. I've found many a USGS report on an area, or NPS geological study, that was extremely helpful in helping me hone in on issues so I could write it up as an earthcache. The trick is finding a more elementary article so I can school myself on the issue enough to be able to take the scholarly article, extrapolate a lesson that can be delivered in an earthcache, and then translating from geologist to lay person.

 

I've found that the Cochise College, Arizona, geology site has some great, easy to understand resources on weathering and other topics. That has really helped me put together several of my earthcaches. And since I lived in Cochise County for a few years when I was stationed at Fort Huachuca, it's a nifty coincidence to me that the site has been so handy.

0

Share this post


Link to post

This is a great discussion.

 

Some resources on the geology of Illinois that might be useful:

 

1) "From the Cincinnati Arch to the Illinois Basin: Geological Field Excursions along the Ohio River Valley", by Maria and Counts

[not sure if that's the right part of Illinois, but it looks good.]

 

2) "Geology Underfoot In Illinois", by Wiggers

 

Anyway, lots of great ideas in this thread. I particularly like egroeg's suggestion to consider this: "what lesson are you trying to give the cachers?"

 

That is the best place to start :)

 

Best wishes,

 

Matt Dawson, GSA

0

Share this post


Link to post

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
Sign in to follow this  
Followers 0