Where Can I Get a Geologic Map of My Property?
Steven Dutch, Natural and Applied Sciences, University
of Wisconsin - Green Bay
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The Short Answer in Most Cases is: You Can't
Here are some reasons why:
- It takes a lot of time and effort to create a really detailed geologic map. Unless your
property was of unusual interest, chances are it hasn't been mapped in detail. If it had
been, odds are you or a previous owner would have known about it as it happened.
- The sorts of features plotted on geologic maps tend to be large. In the vast majority of
cases a geologic map of a single property lot, even a large farm, would contain only a
single geological unit; once in a great while a geologic contact (boundary between units)
might run across a piece of property. Anything more complicated than that would be
- In many places there just isn't enough information to say much specific about the
geology of a single piece of property. In northern Wisconsin, for example, a property
might be entirely buried by glacial deposits. The nearest information about bedrock might
be an outcrop a mile away on one side and a well a mile away on the other. If the bedrock
is the same in both places we are probably safe in assuming it passes under the property
as well. If the bedrock is different we can assume there's a contact someplace between the
two sites, but there's no way of pinning its location down exactly.
What You Can Get:
Although the odds are very much against your finding a detailed map of your specific
property, you can find maps of the surrounding area that include your property:
- The entire United States is covered by topographic maps at scales of 1:24,000
(one inch = 2000 feet, or about 2-5/8 inches per mile). These maps are sold by the U.S.
Geological Survey and many private vendors. Indexes are available for each state.
A geologist can often tell a great deal about the geology of an area from a
- Every state has a geological survey that produces geologic maps. In addition, the U.S.
Geological Survey publishes geologic maps, and also produces indexes that include geologic
maps published elsewhere, for example, in research journals or graduate theses. Map
coverage ranges from very detailed to very sketchy. Only Kentucky is completely covered by
geologic maps at 1:24,000 scale, one per topographic quadrangle.
- Much of the U.S., especially agricultural areas, is covered by soils maps.
These are often drawn onto aerial photographs so that tiny details are visible. Two
warnings are in order. First, soil terminology can be confusing. Second, you may or may
not be able to tell much about geology from a soils map. If the soil formed directly from
the underlying bedrock, you probably can. If it formed from glacial deposits covering the
bedrock, you can't. However, if you're interested in planting the soil, excavating, or
slope stability, a soils map may be just what you want.
- Most states collect well records which are available to the public, and you can
get the records from the vicinity of your property. Well drillers vary a lot in accuracy,
geological knowledge and record-keeping, many old wells may not have been recorded or the
records were lost or misplaced, and wells dug by the property-owners themselves were
probably not recorded. In addition state highway departments have test boring records, and
state geological surveys often have records and samples from research or exploration
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Created 18 September 1998, Last Update
14 December 2009
Not an official UW Green Bay site