Vanishing Clues to an Ancient Wisconsin Natural Disaster

8/11/2019 Vanishing Clues to an Ancient Wisconsin Natural Disaster

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Vanishing Clues to an Ancient Wisconsin Natural Disaster

uriosity is the natural impulse that often leads to new discoveries. It is most certainly true in this

case as well. In the spring of 2010, as hazel brush and brambles were being cleared for an

extension of a vegetable garden, the warm day and the land clearing effort necessitated a pause

atop an large earthen mound that had just been exposed. Family tradition maintained that these lumps areIndian burial mounds. That is simply local mythmaking in the process; it is but quaint lore to excite

youthful wonder. Everyone who is a native of the Northwoods knows that these dirt piles represent the

untimely demise of some grand tree. As the fallen tree decomposes, the earth captured by its vertical

tangled roots forms the mound; the hollow represents the original location of roots and soil. One can

even determine the direction of the trees fall by the relationship between the stump mound1and the

hole. Firsthand knowledge of the creation of such excavations stemmed from the great Riverview

tornado, or as meteorologists named it, the tri-county tornado of June 7th2007.

2 In the vicinity of the

garden project, over 50 maple and bass trees were tipped over in a swath 100 yards wide and a quarter

mile long by an offshoot of this storm. The culprit was straight-line winds, such as was likely responsible

for the stump mound next to my garden. As these factors were pondered atop the pile, several issues

became apparent. The first concerned the shape of the hole associated with the mound; the maple and

bass trees formed rounded holes, three to five feet in diameter, something dictated by their root structure.

This hole was long and oval shaped, indicating a shallow and spreading root system more like that of

pines. The second issue was the very size of the mound itself; it was easily three times bigger than the

fresh damage caused by the Riverview tornado, indicating a far larger tree. From the elevated vantage

point atop the mound, a dozen more large grassy piles were visible all around. More striking was the fact

that all these structures shared the same orientation. That was the moment when the vestigial survivors of

some long forgotten storm made themselves apparent. Being a life-long resident of the area, I know these

mounds (with the same orientation) can be found for miles to the north, south and west.3 These then are

the remains of a blow-down, as they are called by the older folks.4 The direction indicated a force that

came out of the north-west, and tipped all the trees to the south-east. Straight-line winds can be asdevastating as tornadoes or hurricanes, but the damage tends to be narrowly defined. An event able to

topple mature trees over such a wide area strongly indicates something rather significant. Additional

evidence concerning the details of this event was lacking, and what follows in this paper has been taken

directly from notes I began to keep following the day of realization atop the stump-mound.

1This is what I have decided to name them for the sake of this paper.2This tornado was an acknowledged EF-3, and noticeably, either broke trees off some feet off the ground, twisted

them beyond recognition, or pulled them up completely.3The phenomenon appeared at first to end at the Peshtigo River, three or so miles to the east of my garden.4The late woodsman Cater Parker for instance, spoke of one that hunters found years ago somewhere near

Goodman, Wisconsin, that had occurred in the wild without anyone knowing it. He also speculated that the natural

prairie that yet existed in the 1930s, near Grandfather Lake in Marinette county, was the result of a blow-down that

burned.

C


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Report on findings, May 31, 2010

I tilled my garden for the second time(that spring5). I set the depth between 6-8 inches and as I

made my passes from north to south this time (before I was east to west) I hit several pieces of old dirty

wood, included one piece kicked up east of the garden, ten in all. Seven of the pieces bear evidence of

fire, three appear unburned. Two of these (three) are because they are knots; one is a chip, a broken

fragment that displays end grain. All are pine, type of species unknown. The pieces are impregnated

with dirt into the smallest of holes. Some are hollow, the resin of the knot and the charcoal the only

reason for preservation. Some pieces are found by my tiller in a horizontal position, and show the marks

of the tines. Some of the knots I pulled up with my hand from a vertical position. The charcoal is

invariably on the top. One piece that I kicked up ten feet east was closer to the surface than the others, a

bit of moss on the corner was observed. Now these finds cannot be from the conspicuous stump-mound

south of my garden for the tree it represents would have fallen away from my garden. However I recall a

prominent stump mound 30 yards to the north-west of my garden that was plowed out when I leveled my

yard. Pattern is as follows.

Although wood and charcoal may (someday) be found between the stump-mound and garden,

further finds (to the south-east) might actually allow one to determine the height, thus the maturity of the

trees, and by using the facts thus established, calculate the wind-speed necessary to topple such trees. Iintend to section the stump-mound south of my garden to confirm or refute my suspicions

5The site of the garden, begun in 2009, had never been touched, and everything around remains virgin ground.


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Report on excavation of stump-mound Oct 15 th2011

Before we started to dig, we took measurements for accuracy. The stump mound is actually 19

feet long and 8 feet wide measured from the center of the hole to the level ground on the down-wind side.

From the bottom of the hole to the highest part, the mound is 3 feet high. It looks like this:


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I decided to dig directly through the structure diagonally. The facts I wish to demonstrate are:

did the fire occur before or after the tree tipped over? What, if any, remains of root systems might be

found? What was the size and species of the fallen tree? Digging proceeded smoothly, with no stones

encountered. Soil in this area is a loam.6 I paused halfway through to make a sketch of the details that

were emerging. The first noticeable thing was the unbrokenlayer of topsoil, undisturbed, approximately

7 inches thick, covering both the hole and the mound. It is light-brown, and indicates a significantpassage of timesince the stump-mound was formed. Underneath this was a thick layer of orange loam,

10-12 inches thick. This faded to a yellowish tan as it extended down to the old level of brown top-soil.

Another clue was the downward trend of the original topsoil. All the soil layers were exceptionally clear,

no stones, no wood and few organic deposits from small roots (but really not many roots al all). I dug

through the old topsoil layer and continued to the south-east. Soon I came to a light grey layer, followed

by an orange, brown, then very thin black layer. I found the first bit of very decayed wood just inside the

brown layer, followed by a few bits of charcoal. I named this the U shaped feature. The sketch is as

follows:

6United States Department of Agriculture, Soil Survey of Marinette County, Wisconsin, sheet number 48, PaC

stands for Padus fine sandy loam. See soil description for PaCon page 71.


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Findings thus far

It is clear from these excavations that the fire responsible for burning the debris, occurred after

the event in question. The burned debris in the stump-mound is contained in a soil, but soil that was

deposited as the vertical exposed roots decayed. There was no charcoal found within the U shaped

featureitself, as would be if the original sod smothered burning ground debris as the tree fell. The actual

remains of roots suggest that most if not all the roots on the downwind side remained in situ, being bent

or broken off, while the upwind roots were pulled out violently carrying with a large quantity of earth.

The spreading nature of the root evidence indicates a shallow horizontal system, consistent with the great

pines.

The widespread, consistent pattern of stump-mounds is indicative of a onetime disastrous event.

As these mounds are often bisected by railroad grades of the logging period, and erased by settlers fields,

we can safely conclude that they predate the 1870-80s. Also, the hoary age of the massive white pines7

cut in this region would seem to post date this event (i.e. everything had grown back by modern times).

What sort of event was responsible for such destruction? Several scenarios can be proposed while others

can be excluded. A tornado, or several over long periods of time can be safely counted out. Tornadoesleave paths a few miles wide at most, not dozensof miles wide. They also come from different directions,

not just from the north-west. A great wind-storm, blowing for days or weeks with unprecedented fury,

could perhaps create a domino effect; the fall of one tree exposes and weakens its neighbor, and so on.

An epic ice storm could also have weighed down the trees, making them top-heavy and vulnerable to

wind. The fact that they were tippedover violently remains the strongest indicator.

Update 9/5/13

Since this project was started, the vast extent of the disaster has slowly been expanded. While trout

fishing outside of Wausaukee, WI, in 2012, another debris field was found and charred samples dug up.

More wood has been recovered from near Fence and Goodman, WI, in 2013. Most remarkably, similarmounds (again trending north-west to south-east) and ancient pine knots were located near Mellen, WI. 8

The presence of charcoal on almost all these abundant samples would make verifying the age and

distribution of this disaster a rather simple matter.9 As the evidence for this event disappears with

logging, home construction, and road building, a chapter of Wisconsins natural history vanishes as well.

Sabin Rosenbaum 3/2/14

7The number of tree rings on the largest white pines run well into the hundreds. See the MacArthur pine cross-

section at the Forest County courthouse, Crandon, WI.8There is a curious but noticeable variation; mounds located furthest south trend slightly to the south-south-east,

while the northernmost mounds trend somewhat to the east-south-east.9Carbon dating the debris from the disaster would determine fragments of the same approximate age.

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Vanishing Clues to an Ancient Wisconsin Natural Disaster