General Info:
A
sinkhole, also known as a sink, shake hole, swallow hole, or
swallet is a natural depression or hole in the surface topography
caused by the removal of soil or bedrock, often both, by water.
Sinkholes may vary in size from less than a meter to several
hundred meters both in diameter and depth, and vary in form from
soil-lined bowls to bedrock-edged chasms. They may be formed
gradually or suddenly, and are found worldwide. These terms are
often used interchangeably though many will distinguish between
those features into which a surface stream flows and those which
have no such input.
Mechanisms of formation may include the gradual
removal of slightly soluble bedrock (such as limestone) by
percolating water, the collapse of a cave roof, or a lowering of
the water table.
Sinkholes are usually but not always linked with
karst landscapes. In such regions, there may be hundreds or even
thousands of sinkholes in a small area so that the surface as seen
from the air looks pock-marked, and there are no surface streams
because all drainage occurs sub-surface.
Wikipedia defines Karst topography is a landscape
shaped by the dissolution of a layer or layers of soluble bedrock,
usually carbonate rock such as limestone or dolomite.
[1]
Due to subterranean drainage, there may be very
limited surface water, even to the absence of all rivers and lakes.
Many karst regions display distinctive surface features, with
sinkholes or dolines being the most common. However, distinctive
karst surface features may be completely absent where the soluble
rock is mantled, such as by glacial debris, or confined by a
superimposed non-soluble rock strata. Some karst regions include
thousands of caves, even though evidence of caves that are big
enough for human exploration is not a required characteristic of
karst.
This region in Mt Airy Forest:
The sinkholes at the coordinates are a bit
unqiue. There are not
many know karst regions in Ohio. See chart below – the red
regions are known karst regions in Ohio.
The region in Hamilton
county is known as the Ordovician Uplands. This area have surprising
well-developed karst terrain despite the large component of shale
in the local bedrock.
The region derives it name for the rock deposits exposed date back
to the Ordovician time when this are was under a shallow
sea. Below is a map of
rock classification in Ohio.
Fortunately, one of these karst areas with sinkholes is located in
Mount Airy Forest.
Below is a map of many sink holes documented by
Applegate[2].
All the sinkholes in this Mt Airy Forest area are found between the
780- and 810- foot contours on the map. They tend to be <25 meters
across and 3 meters deep. Since this region is mostly shale (65% on
average), it is surprising that the sinkholes are found only where
it is the surface bedrock. Most sinkholes develop
where there greater amounts of rock that are more easily eroded
(i.e. limestone). Most of the sinkholes in this area do not hold
water, even after heavy rains.
Logging requirements:
1)
Take
a photo of it with some personal item (your gps, you, or water
bottle, etc) and post it
In an email to me:
2)
Approximate
the dimensions – diameter and depth
3)
Was
there standing water in the sinkhole?
4)
From
the info above, why is it unusual to find sink holes in our
region?
Below is a trail map of this area of Mt. Airy Forest.
[1]
"Glossary of Cave and Karst Terms". Speleogenesis.info.
http://www.speleogenesis.info/glossary/. Retrieved
2009-05-04.
[2] Patrick Applegate
- Detection of sinkholes developed on shaly Ordovician limestones,
Hamilton County, Ohio, using digital topographic data: Dependence
of topographic expression of sinkholes on scale, contour interval,
and slope. Journal of Cave and Karst Studies 65(2): 126-129.,
PATRICK APPLEGATE,Department of Geology, University of Cincinnati,
Cincinnati, Ohio 45221 USA,