Earthcache Logging Requirements

[+vw_k]

Hi Everyone,

 

I'm planning on creating an Earthcache at a river crossing where the flow of the river has lessened due to water disappearing down "swallow holes" into the underlying chalk in the area, I have some interesting geological and historical information on this phenomenom to put on the cache page to educate visiting cachers.

 

There are no information boards at the feature itself, I was thinking of having the following logging requirements:

 

1) Take a photo that includes yourself or your GPSr at the cache site with the river in the background.

2) Estimate or measure the width of the river at this point, noting the method you used to get this measurement.

3) Measure the depth of the river at it's centre.

 

The crossing of the river is made of "stepping stones" which would enable cachers to access the centre section of the river to measure the width and depth.

 

Would these requirements, along with the geological and historical information on "swallow holes" I supply on the cache page be enough to create an earthcache?

 

Any suggestions would be welcomed, thanks.

 

Dave

[+Accordiongal]

Hi Everyone,

 

I'm planning on creating an Earthcache at a river crossing where the flow of the river has lessened due to water disappearing down "swallow holes" into the underlying chalk in the area, I have some interesting geological and historical information on this phenomenom to put on the cache page to educate visiting cachers.

 

There are no information boards at the feature itself, I was thinking of having the following logging requirements:

 

1) Take a photo that includes yourself or your GPSr at the cache site with the river in the background.

2) Estimate or measure the width of the river at this point, noting the method you used to get this measurement.

3) Measure the depth of the river at it's centre.

 

The crossing of the river is made of "stepping stones" which would enable cachers to access the centre section of the river to measure the width and depth.

 

The swallow holes are known as "sinking streams" in SE Minnesota. My thought would be to include q and a about the sinking stream process. What creates differences in the seasons? Spring, Summer, Fall, Winter.

 

The questions you list are related to measuring the stream in general, not about the "Swallow holes". I think the logging requirements should be related to the swallow holes. Consult with the local county geologist, they are full of information and can give you ideas on how to approach the logging requirements.

 

Good luck.

 

Would these requirements, along with the geological and historical information on "swallow holes" I supply on the cache page be enough to create an earthcache?

 

Any suggestions would be welcomed, thanks.

 

Dave

[+Cav Scout]

The questions look good, simple and to the point, However I would change the question about the depth of the river to "estimate depth" of the river.

 

The photo requirement should have (face included), unless you don't mind hand shots .

[+Juicepig]

The questions look good, simple and to the point, However I would change the question about the depth of the river to "estimate depth" of the river.

 

 

I have a cache that requires "measure depth of river", and provide people with a means of doing so; I hid a metal sign post and some rope nearby, they tie it together and drop it off the bridge.

 

 

I found this to be one of the best types of logs - dynamic! since people can put their answers in the log entry itself without having to email me for confirmation. The height of the river varies from 1m deep to about 6m deep depending on the season

[+GEO WALKER]

Just a thought…

 

Since the main event seems to me to be the change in stream flow, would a flow measurement be better? Is there an area upstream w/ greater flow rate than an area downstream from the “swallow holes”?

Perhaps have the cacher establish a distance 1 above and the other below the "swallow holes". Throw in a floatable object stick or leaf. Time the event. Have the cacher submit the two flow rates and perhaps calculate the difference in those rates, thus illustrating the effect of the “swallow hole”.

[+TerryDad2]

They could also get a depth above and below the swallow hole to compare the volume of water in the river before and after the hole.

 

Just a thought…

 

Since the main event seems to me to be the change in stream flow, would a flow measurement be better? Is there an area upstream w/ greater flow rate than an area downstream from the “swallow holes”?

Perhaps have the cacher establish a distance 1 above and the other below the "swallow holes". Throw in a floatable object stick or leaf. Time the event. Have the cacher submit the two flow rates and perhaps calculate the difference in those rates, thus illustrating the effect of the “swallow hole”.

 

I would expect the velosity of the water to be very similar above and below the hole so long as the slope remains constant on either side of the hole.

[+vw_k]

Thanks for all the suggestions. I think measuring the depth of the river would be fine as it is only about a foot deep at the crossing and so cachers could dip a stick or walking pole into the water, they could then measure or estimate the amount of the stick that is wet.

 

Unfortunately it is not easy to access the river further upstream or downstream, the location where the stepping stones cross the river is one of the only convenient places where the public have access.

 

I may add a question such as "what changes would you expect to see in the river further upstream/downstream from hthis location?"

[Neos2]

I agree with GEO WALKER, it really might be better to ask a question about volume of water flowing at the point you place the EarthCache.

 

If the purpose of an EarthCache is to teach about the Earth, it's probably best to teach about the feature the EarthCache is pointing out. In this case, you aren't focusing on what made the river that deep, but on how the swallow holes impact the volume of water flowing in the river. The major impact they have is to lessen the flow of water in the river.

 

In some places rivers actually "disappear" into swallows and become "Lost Rivers" for miles and miles. Swallow holes occur in carbonate rocks (limestone, chalk, etc). The acidity of the water causes the carbonate rocks to dissolve, forming the hole. That lets the stream drop into into underground channels, resulting in diminished the flow of the river on the surface downstream of the swallow hole.

 

It would be easily done, and could still use the cool stepping stones. All you would need to do is to supply the information about the volume of the flow of the river upstream (and optionally downstream as well) and tell folks how to estimate the change in the volume by the time it gets to the EarthCache.

 

For instance, the average flow of the Mole drops from 63 million gallons a day above Burford Bridge to about 55 million gallons a day downstream at Leatherhead. At the site, the folks measure the flow rate in the center of the stream, then using the depth and the breath of the water, they calculate the volume of water per day at that point.

 

The amount will vary a bit with rainy weather etc, but they should get a reasonable volume---and even if they are quite a bit off (Math errors or bad estimation) they will still have learned how to calculate flow rate and estimate volume and come to appreciate the difference in the volume before and after the swallows. You can still give them credit for doing the process correctly. That's a good lesson in any teacher's book!

[+vw_k]

Thanks for the suggestion, Neos, how did you know I was studying the river Mole?

 

I really like the idea of measuring the flow rate of the river at the earthcache. How would cachers actually measure the flow rate at the centre of the stream? I've found some schoolteachers guides online that suggest dropping something bright and biodegradeable (such as a tomato or orange) into the water and measuring the time it takes to travel a certain distance. Would this be acceptable for an earthcache? I'm a little hesitant to encourage people to drop things into the river, even if they are biodegradeable, that cannot be recovered afterwards.

Edited October 29, 2008 by vw_keychain

[+GEO WALKER]

I haven’t had a chance to take my nephew, who actually lives in South Bend, out on this one yet. Perhaps this may lend itself to an idea or two:

Blazer / Charger Confluence by T_Bird (GC13FAC) Indiana

 

As for an environmentally friendly floatable object, any vegetation, leaf, reed or a blade of grass should do the trick.

Here’s a SWAG of an Idea… Use some type of “line” like fishing line w/a prescribed length. Tie a float to the other end and calculate the time to the end of the line? Please make a note that they have to hold on to the other end.

 

Just for grins and giggles, you may also have them do a volumetric test by timing the filling up of a container say gallons or liters /minute. This approach is popular w/springs.

 

This way they can see both the speed and volume of the stream.

 

These methods should be inexpensive enough to most folks.