Pigeon River Country Sinkholes EarthCache
Hidden : 5/26/2010
Difficulty:
2 out of 5
Terrain:
2 out of 5

Size: Size: not chosen (not chosen)

Join now to view geocache location details. It's free!

Watch

How Geocaching Works
Looking for a different adventure?

Please note Use of geocaching.com services is subject to the terms and conditions in our disclaimer.

Geocache Description:


This Earthcache is located in the Pigeon River Country Forest (PRCF).

We wish to thank the Michigan Department of Natural Resources for allowing us to place this Earthcache in the Pigeon River Country Forest.
Big thanks also go out to my brother, Ramblin Rumble and cousin, Big Johnson for taking us back to all of these locations, after we had already done the geocaches, in order to get the information needed to place this Earthcache.

The PRCF Unit is the smallest (105,049 acres) of the 15 Units in the State Forest System. The PRCF is in the heart of Michigan's elk range.
The PRCF has 6 campgrounds, one horse trail campground and a group horse camp. Hiking and riding trails are maintained in the Unit. Bicycle riders and cross country skiers are welcome to use the trails. It is a place to geocache, hunt, fish, camp, hike, cross country ski, snowshoe, ride a horse or just take a drive. The PRCF is home to a wide variety of wildlife ranging from elk, coyotes, bears, bald eagles and songbirds. It is also home to the white pine, red pine, cedars, Beech and Maple trees. The PRCF is still a fairly wild place with many contiguous sections with neither roads or trails, allowing for a North Woods experience guaranteed to be people-free.
Three rivers flow through the PRCF Unit: the Pigeon, Black and Sturgeon Rivers. The Pigeon River is a designated Natural River.

One of the special features of the Pigeon River Country Forest is its sinkhole lakes.

The most important part about this Earthcache is not to climb the vertical walls surrounding the sinkholes. This un-neccessary foot traffic will accelerate the erosion process. All of the sinkhole lakes have footpaths around them. Please stay on the trails. Some of the sinkholes you will visit, will take you to the waters edge.

Sinkholes are usually, but not always linked with Karst landscapes. Karst refers to a topography shaped by soluble layers of bedrock like limestone and shale. Karst terrains are characterized by caves, steep valleys, sinkholes, and a general lack of surface streams because drainage is underground. A karst landscape has springs, sinking streams, caves, and sinkholes.

A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, is a natural or unnatural depression or hole that begins with underlying bedrock of limestone and shale. This area of NE Lower Michigan is made up of limestone and shale which was laid down between 345 and 395 million years ago (in the Devonian Period). The upper most layer of bedrock consists of limestone of the Traverse Group.
See Figure 1 below.

Sinkholes are formed by the dissolution of the soluble rocks, limestone and shale which are easily dissolved by acid water and is eroded into what is known as "karst" formations, which often contain underground streams and subsurface limestone caves.
See figure 2 below.

When the limestone is dissolved by slightly acidic water, probably by an underground river aided by rainfall, it carves out large caves and caverns in the limestone. Some of these caves collapse in on themselves creating the sinkholes that are located here at PRCF.
See Figure 3 below.



Some sinkholes are simply deep depressions, sometimes found in a line where an underground stream flows beneath. Such are the dry sinkholes just east of Shoepac Lake a few miles south of Onaway. Others, where the bottom of the sinkhole becomes plugged with marl or other less permeable material, form lakes like the ones here in the PRCF. The PRCF sinkhole lakes are sustained by underground springs.

Many mechanisms can form sinkholes including the slow removal of soluble bedrock (such as limestone) by underground water, the collapse of a cave roof, or when there is a natural (or unnatural) lowering of the water table. Occasionally a sinkhole may form in urban areas from human activity when a sewer line collapses or from a water main break.

Of the even sinkhole lakes in the PRCF, six of them are of the classical round sinkhole type with very steep banks. These six are: Devil’s Soup Bowl (the smallest of the lakes), Lost Lake, North and South Twin Lakes, Section Four Lake and West Lost Lake. The water of these six is typically milky blue-green. That is because they are reflecting their dissolved limestone origins and are fed mostly by underground springs. Hemlock Lake, while it has the typical steep bank along its eastern and southeastern shore, has some more gradual, even swampy shores. The depths of these lakes range from 30 to 60 feet, quite unusual for such small lakes in country with such sandy or gravelly soil.

We would love to have you take a picture of you (or your team) and/or your GPS in front of one of your favorite sinkhole lakes. Please label the picture or post in your log which sinkhole lake you are at.

POSTING REQUIREMENTS:



Waymark #1 - Section Four Lake
The posted coordinates will bring you to the 1st of the 7 Sinkhole Lakes of PRCF. This is known as Section Four Lake. At this location, email us the number of boulders that are placed to the left as you face the Lake Sign. Also describe the color of the water in this lake.
Email your answer as #1

Waymark #2 - Twin Lakes
The second stop is North and South Lake or Twin Lakes. At this waymark location, you need to email us your estimate of the distance between the North and South Lakes, known as Twin Lakes.
Email these answers as #2

Waymark #3 - Devils Bowl
The next stop is at the smallest of the sinkhole lakes. At the listed waymark coordinates, take an elevation reading. Now you need to take the path to the lakes edge and take another elevation reading.
Email us the 2 readings and the difference in the elevation as #3

Waymark #4 - West Lost Lake
The next sinkhole to visit is West Lost lake. This is one of the lakes that has easy access as the coordinates take you to the waters edge. Here, take a temperature reading of the water. We also would like your actual (by hiking the path around the lake) or estimate of the distance across this lake.
Email these answers as #4.

Waymark #5 - Lost Lake
Your next stop will be at Lost Lake. At this location, tell us the type of tree to the left of the Lake Sign and also tell us the circumference of this tree.
Email these answers as #5.

Waymark #6 - Hemlock Lake
The last stop in this Earthcache is Hemlock Lake. At this location, tell us if this is a 'soil and tree bowl' or a 'bedrock edged chasm' type of sinkhole.
Email this information as #6.

Reference information links:
The United State Geological Survey
Wikipedia
Michigan Department of Natural Resources



Team Rumble has earned GSA's highest level:


Please remember to:
TAKE ONLY PICTURES AND LEAVE ONLY FOOTPRINTS

Be sure to check out the Earthcache Master program at Earthcache Masters

Additional Hints (No hints available.)



Attributes

No attributes available

Advertising with Us

Inventory

There are no Trackables in this cache.

View past Trackables

What are Trackable Items?

Bookmark Lists

View all bookmark lists...