U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2009–1188

December 2009 Printed on recycled paper

Open bedrock fractures were mapped in and near two brine field areas in Tully Valley, New York. More than 400 open fractures and closed joints were mapped for dimension, orientation, and distribution along the east and west 

valley walls adjacent to two former brine fields. The bedrock fractures are as much as 2 feet wide and over 50 feet 

deep, while linear depressions in the soil, which are 3 to 10 feet wide and 3 to 6 feet deep, indicate the presence of 

open bedrock fractures below the soil. The fractures are probably the result of solution mining of halite deposits about 

1,200 feet below the land surface.

Land-Surface Subsidence and Open Bedrock Fractures 

in the Tully Valley, Onondaga County, New York

Bedrock fractures have opened in response to subsidence over a former solution-mined area. Subsidence is occurring beyond the left side of the 

photograph, and has caused these formerly closed bedrock joints to become open bedrock fractures as the rock mass moved to the left.
2

Introduction

In the late 1880s, solution mining of halite (rock salt) beds in 

the southern Tully Valley produced brine used by the Solvay Process 

Company to manufacture soda ash in Syracuse, N.Y. During the 

nearly 100 years of solution mining, approximately 150 vertical 

feet of halite were removed from layers 1,200 feet below the valley 

floor. Underground solution cavities collapsed, eventually causing 

land-surface subsidence in the solution-mined areas. The adjacent 

bedrock valley walls responded to this subsidence by creating open 

bedrock fractures that follow naturally-formed joint orientations in 

the bedrock. 

The purpose of this report is to document the character of 

open bedrock fractures and closed joints in relation to regional joint 

orientations in and near the two brine fields. A brief history of the 

brine fields and associated subsidence is presented. The fractures 

and joints are described, and their location and orientation are shown 

in maps and joint rose diagrams.

Geology of the Tully Valley

The Tully Valley near Syracuse, N.Y., is a 6-mile-long glacially 

scoured trough located in the eastern Finger Lakes region of the 

Allegheny Plateau (fig. 1). The bedrock walls of the valley are 

Middle Devonian Hamilton Group shales, and the floor of the 

bedrock valley is Lower Devonian Helderberg Group limestones 

and dolomites. Upper Silurian Salina Group shales and evaporites, 

including halite (rock salt) deposits, are about 1,200 to 1,400 feet 

below land surface at the southern end of the valley. Multiple glacial 

advances and retreats between 1.6 million and about 11,000 years 

ago (Rogers, 1991) widened and deepened a pre-existing river 

valley, and deposited more than 400 feet of clay, silt, sand, gravel, 

and till in the bedrock trough (Kappel and Miller, 2003).

Tully Valley Brine Field History

In the late 1880s, the Solvay Process Company established 

a chemical industry along the southern shore of Onondaga Lake 

to manufacture soda ash using the region’s halite and limestone 

resources. The concentration of salt in brine springs and wells along 

the shores of Onondaga Lake diminished due to nearly 130 years 

of brine withdrawal (1790s to late 1920s) for soda-ash production, 

forcing the Solvay Process Company to find a new source of brine 

(Kappel, 2000). A number of deep exploratory boreholes were 

drilled and halite was found at a depth of 1,200 feet below land 

surface in the southern end of the Tully Valley about 15 miles south 

of Syracuse (fig. 1). 

Solution mining began in the Tully Valley in 1888. Initially, 

solution-mining wells were drilled into the uppermost halite layer 

(about 45 feet thick) in several well clusters within the east and west 

brine fields (fig. 2). Three additional halite beds were discovered 

below the first bed, and these additional beds were solution mined 

as the soda ash industry grew. Solution-mining wells are used to 

extract salt by pumping freshwater into the halite bed, dissolving 

the halite into saturated brine, then pumping the brine from the 

dissolution cavity. This method of brine removal was made more 

efficient through the “undercut method”—injecting water into the 

lower beds while connected to the upper, previously solutioned 

beds that already contained partially saturated brine. Additionally, 

drilling wells to follow the natural dip of the halite beds (dipping to 

the south) allowed the dissolution cavities to connect in a downslope 

Onondaga Creek

Eme rson Gulf

Onondaga Creek

Rainbow Cr eek

Rattlesnake Gulf

Onondaga Creek

Otisco Road

Tully Farms Road

New York Route 11-A

BARE MOUNTAIN

U. S. Route 20

DUTCH HILL

76°10' 76°07'30"

42°52'30"

42°50'

Base from Otisco Valley and

South Onondaga, N.Y.

Quadrangles, 1955, 1:24,000

 County

NEW

YORK

Study

Syracuse

Onondaga

 Area

Location map

Tully

Finger Lakes

Region

Interstate I-81

U.S. Route 11

Solvay 

Road

New York Route 80

Mud

boils

Valley walls

Valley floor

EXPLANATION

0 .5 1.0 1.5 MILES

0 .5 1 1.5 KILOMETERS

Webster Road

East 

brine 

field

West 

brine 

field

Joint/fracture data—location is outside

the brine field area

Tully Valley brine field

Stream channel—arrow shows

direction of flow

Area shown in 

figure 2

Area shown in 

figure 5

Figure 1. Physiographic features in the Tully Valley, 

Onondaga County, N.Y.
3

West

brine

field

East

brine

field

Emerson Gulf

Onondaga Creek

Tully Farms Road

State Route 11A

Location of

Figure 3

Location of

Figure 4

EXPLANATION

Solution-mining well

Stream channel—arrow 

indicates direction of flow

Tully Valley brine field

0 0.1 0.2 MILE

0 0.1 0.2 KILOMETER

Solvay Road

North American Datum of 1983; Universal Tranverse mercator projection, Zone 18N;

Orthoimage base from New York State Office of Cyber and Critical Infrastructure Coordination, Spring 2006.

Figure 2. Locations of solution-mining wells in the Tully Valley brine field, Onondaga County, N.Y. 

(Location shown in figure 1.)
4

direction as new solution-mining wells were drilled farther to the 

north, further increasing brine-removal efficiency (Yanosky and 

Kappel, 1998). Early solution mining techniques did not leave 

walls or pillars of halite to support the overlying bedrock and, 

therefore, increased the possibility of bedrock collapse within 

the solutioned halite layers as well as in the overlying bedrock.

 Brine production in the Tully brine fields peaked during 

1950–60, before the east brine field was closed in 1960 due 

to the amount of land-surface subsidence that had occurred in 

this field. The west brine field was used for production until 

1988. During the 94-year history of brine removal, more than 

160 solution-mining wells were drilled (fig. 2) and more than 

96 million tons or approximately 31,000 acre-feet of halite 

were removed from the southern Tully Valley—enough to fill 

Syracuse University’s Carrier Dome sports complex 35 times 

(Kappel, 2000).

Subsidence History in the Brine Field 

Collapse within solution cavities occurred early in the brine 

mining process. In a historic retrospective of the Tully brine field 

written in 1950, the subsidence problem was described (The 

Solvay Process Company, 1950).

“During the years 1889 and 1890, thirty-one wells 

were drilled along the east side of the valley and 

extending about a mile and a half northerly from the 

first well. ***Most of the East Side wells, however, 

were drilled thru [sic] the top salt bed only, and 

because this bed was only 40 to 50 feet thick, it was 

necessary, in order to obtain suitable capacity for 

strong brine, to feed water to the top of the salt bed and 

to draw brine from the bottom. Because of this, and 

because there is 150 feet of Shale Rock immediately 

above the top salt, early and frequent caving [rock 

falling from the roof of the brine cavities] resulted.”

This report (The Solvay Process Company, 1950) also 

indicates that in 1929, a new method of air-padding (placing a 

volume of air at the top of the solution chamber to prevent the 

removal of halite from the roof and the collapse of the overlying 

bedrock) and drilling “undercut” wells in the lower halite layers 

was used to further increase brine production. The “undercut 

method” was initially successful in producing greater quantities 

of brine, but cavern collapse and subsequent subsidence of the 

land surface in the east brine field was noted.

“For the past several years [1940s] a general 

subsidence of the ground has been noted at the 

Looking downward into an open bedrock fracture which is about 30 feet 

deep. The left face has pulled away from the right face of the bedrock 

fracture in response to land-surface subsidence in the former brine field.

An open fracture showing the uphill face on the left and the downhill face 

on the right. The saw-tooth pattern of the right face of the fracture shows 

the close proximity of two intersecting joint sets in the bedrock.
5

east side wells but more particularly in the vicinity 

of the S–1, S–2 group of undercut wells. In 1943, 

it was noted that fissures were being opened up in 

the rock on the side hill along these wells. ***In 

January, 1949, without any previous warning, the 

ground at the north of D-Group, in the vicinity of 

the S–3, S–4, S–5 undercut wells suddenly dropped 

down***. This “Sink Hole” is about 200 feet in 

diameter and 60–65 feet, deep and filled up with 

fresh water. ***a gradual subsidence still continues 

toward the side hill***.”

A 1960 Tully Brine Field report indicated that subsidence 

was an early problem (The Solvay Process Company, 1960).

“It has been noted as early as 1928 that when the 

‘C’ Group wells were drilled up on the hillside 

[East Field area], subsidence encountered from 

the lower ‘C’ wells caused the shale on the hillside 

to creep towards the area of subsidence. This 

effectively cut off or plugged uphill wells.”

Further on: “By using this method of top feeding 

[slotting a well casing above the top halite layer 

and allowing a concentrated brine from the upper 

halite chamber to flow down into the lower halite 

layers] it is probably [sic] that we weakened and 

widened the overall top support for the field, and 

this allowed for the top to cave in. These generally 

subsided gradually and only the areas where 

brine [halite] had been removed from the lower 

level through the upper level where large sink 

holes developed.”

Some areas on the valley floor subsided as much as 

40–50 feet over several decades (CS Consulting Engineers, 

1992). Subsidence observed on the valley floor above each brine 

field was widespread, and open bedrock fractures appeared 

upslope on the valley walls. (In this report, “closed joint” 

indicates a natural crack or joint that is visible only as a thin 

crack in the bedrock surface, and “open fracture” indicates a 

closed crack or joint that has opened by several inches or feet to 

reveal two opposing bedrock walls.)

Regional Bedrock Fracture Pattern

Exposed bedrock along the Tully Valley walls have closed 

joints (cracks) that are parallel to joint sets of the broader Finger 

Lakes region. Parker (1942) documented three orientations of 

joints: Set I striking roughly N. 10°W., Set II striking roughly 

east-west, and Set III striking roughly N. 65° E. in central 

Open bedrock fracture adjacent to the west brine field, showing an open 

bedrock fracture above, with soil still bridging the open fracture below.

Bedrock floor of Emerson Gulf above the Tully Valley, showing the 

influence of closed bedrock joints on the erosion of the bedrock surface. 

This section of stream channel does not lose flow to the closed joints.
6

New York. Sets I and II likely developed during the Alleghanian 

Orogeny (the collision of the African and North American 

continents between 320 and 260 million years ago), as they have 

a geometric relation to other geologic structures of that time 

(Parker, 1942; Engelder and Geiser, 1980). The origin of Set III 

is problematic. Detailed work on the Set III joints in the Finger 

Lakes region of New York revealed that these joints are offset 

by Sets I and II, and thus pre-date the Alleghanian Orogeny 

(Engelder and others, 2001). These closed bedrock joint sets 

are ubiquitous in the region, and pre-date the glacial origin of 

the valley. 

Land-Surface Subsidence

Land-surface subsidence in the Tully Valley has occurred 

in various forms and is related to several different geologic 

processes. In the brine-field area, the removal of a composite 

150-foot thickness of halite at depths greater than 1,200 feet 

below land surface without leaving any physical support within 

the solution cavities causes two general types of subsidence. 

Large, broad-scale subsidence known as “bulking subsidence” 

(Fernández, 1992) causes a gentle sagging of the entire bedrock 

sequence and overlying land surface that can occur over a period 

of years to decades. This type of land-surface subsidence can 

range from a few feet to a few tens of feet over an area of tens 

to hundreds of acres. A second, more localized, smaller-scale 

subsidence known as “chimney subsidence” (Fernández, 1992) 

generally forms sink-like depressions in the land surface over 

a period of hours to days. The resulting sinkhole can be tens of 

feet deep and limited initially to an area of just a few acres, but 

can grow deeper and wider over time to cover tens of acres. 

Land-surface subsidence is generally described by 

terms related to vertical and horizontal movement seen at the 

land surface. Van Sambeek (1996) described these terms as 

subsidence, slope, curvature, and horizontal strain. The last 

term describes the compression or extension of the ground due 

to differential horizontal movement. Generally, compressive 

horizontal strain (causing buckling and bowing) occurs inside 

the perimeter of the mine (or solution cavity in the Tully Valley), 

and tensile strain (causing separation and cracking) occurs just 

outside the mine or solution-cavity perimeter (fig. 3). During 

the nearly 100 years of solution mining and related land-surface 

subsidence in the Tully Valley, the bedrock adjacent to the brine 

fields developed open fractures along orientations of formerly 

closed bedrock joints (fig. 4) as a result of tensile strain as the 

collapse of bedrock has progressed from the solution cavity up to 

the land surface.

Investigation of Open Fractures in the Tully Valley 

Aspects of surface subsidence and related fractures in 

the Tully Valley area such as the dimensions, orientations, 

and distribution of the open fractures, were mapped along the 

east and west valley walls adjacent to the brine fields (figs. 5 

and 6, respectively). The open fractures can be seen clearly in 

the bedrock or observed as linear depressions in the shallow, 

overlying soil. Open bedrock fractures are from 0.33 to 2 feet 

wide and from 2 to more than 50 feet deep. Linear depressions 

in the soil typically are 3 to 10 feet wide, and 3 to 6 feet deep. 

These linear depressions reflect collapse of soil into an open 

bedrock fracture and can exhibit “bridges” of soil between open 

Shale bedrock

with bedding

planes

Unconsolidated sediments

Valley floor

Valley

wall

Sinkhole with water

in base

Solution cavity

Zone of bedrock

fracturing and 

subsidence

Zone of unconsolidated

sediment subsidence

Zone of 

tension -

bedrock

fractures

open here

Former valley floor

Former bedrock surface

Halite beds

Figure 3. Conceptual drawing of subsidence under the floor of 

the Tully Valley, Onondaga County, N.Y., due to solution mining of 

deep halite layers, showing sag and subsidence in the bedrock 

above the solution cavity, the resulting sag at the land surface, 

and the opening of bedrock fractures along a “zone of tension” 

along the adjacent valley wall.

gaps where the soil has fallen into the fracture, locally known as 

“coffin holes.” The total lengths of all linear features can range 

from tens of feet to more than 500 feet. On both sides of the 

valley, the open bedrock fractures generally are limited to the 

lower portion of each slope—below an altitude of about 910 feet 

along the east valley wall, and below an altitude of about 

970 feet along the west valley wall.

Brine Field Open Fractures and ValleyFloor Subsidence 

Fractures are present along the perimeters of both brine 

fields—more than 400 open fractures and closed joints were 

mapped adjacent to the two brine fields (see the Joint Rose 

sidebar). The dominant set of open fractures strikes just west of 

north corresponding to Set I of Parker (1942) (see figure SB1–1 

in the joint rose sidebar.) A less prevalent set strikes 

approximately N. 60°–70° E., corresponding to Set III of Parker 

(1942), and a few east-west striking fractures also were recorded 

corresponding to Set II of Parker (1942). The orientation of 

open fractures and closed joints outside the brine field area are 

shown in figure SB1–2; the orientation of fractures and joints in 

the west and east brine fields are shown in figures SB1–3 and 

SB1–4, respectively.
7

A

B

Imagery by Pictometry International Corporation

Imagery by Pictometry International Corporation

Figure 4. Major fractures above the Tully Valley brine fields: (A) near the north end of west brine field and (B) above the 

central sinkhole in the east brine field, Onondaga County, N.Y. (Arrows indicate location and orientation of large fractures 

on the lower hillside above each brine field.)
8

State Route 11A 

EXPLANATION

Open fracture—

line indicates orientation

Closed joint -

line indicates orientation

Solution-mining well

0 250 500 FEET 

0 50 100 METERS

Sinkhole—location

and size are approximate

Water body in sinkhole

East 

brine 

field

West 

brine 

field Emerson

Gulf

This figure

North American Datum of 1983; Universal Tranverse mercator projection, Zone 18N;

Orthoimage base from New York State Office of Cyber and Critical Infrastructure Coordination, Spring 2006.

Figure 5. Location of open fractures and closed joints upslope from land-surface subsidence and 

sinkholes in the east brine field of the Tully Valley, Onondaga County, N.Y. (Location shown in figure 2.)
9

Emerson Gulf

Tully Farms Road

West 

brine 

field

Emerson

Gulf

This figure

East 

brine 

field

North American Datum of 1983; Universal Tranverse mercator projection, Zone 18N;

Orthoimage base from New York State Office of Cyber and Critical Infrastructure Coordination, Spring 2006.

Onondaga

C reek

Sinkhole—location and

size are approximate

Water body in sinkhole

EXPLANATION

Open fracture—line

indicates orientation

Closed joint—

line indicates orientation

Solution-mining well

Stream channel—

arrow indicates

direction of flow

 FEET

 METERS

0 250 500

0 50 100

Figure 6. Location of open fractures and closed joints upslope of land-surface subsidence and sinkholes in the west brine field of 

the Tully Valley, Onondaga County, N.Y. (Location shown in figure 2.) 
10

Figure SB1–1. Orientation of open fractures and closed 

joints in the Emerson Gulf stream channel, Tully Valley, 

Onondaga County, N.Y.

Figure SB1–2. Orientation of open fractures and 

closed joints for locations outside the Tully brine field 

area, Tully Valley, Onondaga County, N.Y.

A Rose by any other name is but a Rose......

Joint rose diagrams are used by geologists to display 

field data, in this case the orientation and number 

of joints or fractures found in the bedrock in and 

around the Tully Valley. Each rose diagram is broken 

into 5-degree compass increments, and the number 

of joints present within each increment is indicated 

by the distance from the center of the joint rose. All 

compass orientations are measured east or west of 

north—for consistency, the mirror image of these 

readings is shown in the southern half of the joint 

rose diagram.

Three major joint orientations were mapped by 

Parker (1942) for the Finger Lakes region: Set I 

strikes roughly N. 10° W.; Set II strikes roughly 

east-west; and Set III strikes roughly N. 65° E. In the 

Emerson Gulf–All Fractures and Joints rose diagram 

(sidebar figure SB1–1a, upper left), the three major 

joint orientations, number of joints and fractures, 

and compass directions are shown. For all the rose 

diagrams presented in this report, joint Sets I and III 

appear to be well represented, while several other 

orientations are also present. 

The open bedrock fractures present adjacent to 

the brine field generally follow these preferred 

joint orientations and are a natural response to 

solution-mining-induced subsidence and subsequent 

sinkhole development.

Closed joints

n = 179

0

45

90

135

180

225

270

315

0

Open fractures

n = 46

0

45

90

135

180

225

270

315

0

All open fractures and closed joints

n = 225

Set II

0

Set I N

45

135

180

225

315

0 30

Set III

26

31

14

6

1

3

23 28

9

4

S

W 90 E

Emerson Gulf

All open fractures and closed joints

n = 214

0

45

90

135

180

225

270

315

0 40

Locations outside the Tully brine field

(DeGroff, 1950)

1−1a

1−1b

1−1c

270

18

10 20

10 20 30

10 20 30

10 20 30
11

Closed joints

n = 42

Open fractures

n = 119

All open fractures and closed joints

n = 171

East Brine Field

Closed joints

n = 45

All open fractures and closed joints

n = 136

Open fractures

n = 89

West Brine Field

0

45

90

135

180

225

270

315

0 4 8 12 16

0

45

90

135

180

225

270

315

0 4 8 12 16

0

45

90

135

180

225

270

315

0 4 8 12 16

0

45

90

135

180

225

270

315

0 4 8 12 16

0

45

90

135

180

225

270

315

0 4 8 12 16

0

45

90

135

180

225

270

315

0 4 8 12 16

Figure SB1–3. Orientation of open fractures and 

closed joints in the west brine field area, Tully Valley, 

Onondaga County, N.Y.

Figure SB1–4. Orientation of open fractures and 

closed joints in the east brine field area, Tully Valley, 

Onondaga County, N.Y.
12

In the east brine field, open fractures are grouped adjacent 

(just uphill to the east) to three sinkhole areas (fig. 5). In the 

west brine field, a similar relation between open fractures and 

sinkhole development is noted where bedrock fractures are 

grouped adjacent (just uphill to the west) to the three major 

sinkholes (fig. 6), although along the west valley wall, the 

open fractures are present in a more consistent pattern near 

the sinkholes. Neither brine field has substantial open bedrock 

fractures to the north or south of the current sinkholes despite 

the presence of many former solution-mining wells north or 

south of the major sinkhole areas. The location of the sinkholes 

is north of a reported east-west trending geologic structure 

within the halite unit; the structure is possibly associated with 

salt deformation near the northern edge of the halite deposition 

margin, typically described as a décollement or sliding surface 

created by the halite (Rickard, 1977). CS Consulting Engineers 

(1992) reported that the halite beds are thicker to the north of 

this structure and are thinner to the south as the sliding surface 

may have “piled up” salt that was south of the structure and 

pushed it into the salt north of the structure. Therefore, in the 

area with a thicker sequence of halite, larger halite cavities 

were formed, which affected the amount and degree of 

overlying bedrock subsidence, and created the sinkhole areas 

and subsequent fracturing of adjacent bedrock. CS Consulting 

Engineers (1992) reported that this structure, a possible reverse 

fault, is aligned roughly N. 74° W., nearly parallel with and 

south of Solvay Road (figs. 1 and 2).

The only open fractures observed outside of the east and 

west brine fields are about 2 miles north of the east brine field at 

nearly the same altitude. A small cluster of open fractures was 

first reported by Robert Snavlin in 1948 to be present east of his 

farm (Robert Snavlin, private citizen, written commun., 1968). 

These fractures are similar to the open brine field fractures in 

all aspects except that they are not associated with any sinkhole 

development farther downslope from them. 

Other Joints and Fractures Mapped near the 

Brine Field Area

Joints and fractures within and adjacent to the Tully Valley 

were mapped by DeGroff (1950), and their orientations are 

displayed in the rose diagram (fig. SB1–2). Fracture orientations 

in three stream valleys (Rattlesnake Gulf, Rainbow Creek, and 

Onondaga Creek at Fellow Falls) and a bedrock outcrop along 

U.S. Route 11 just north of New York Route 80 (fig. 1) were 

compared to the fracture orientations in the two brine fields 

(figs. SB1–3 and SB1–4). Results of the DeGroff (1950) analysis 

of all fractures and joints (open and closed) within and adjacent 

to the Tully Valley (SB1–2), indicate that joint orientations are 

similar to those mapped in the brine fields (figs. SB1–3 and 

SB1–4) and to those mapped throughout the Finger Lakes region 

by Parker (1942).

In a fourth stream valley at Emerson Gulf (figs. 1 and 7), 

mostly closed joints and some open fractures were mapped 

(SB1–1). Although many of the joints were mapped near the 

western wall of the Tully Valley opposite one of the large 

sinkholes in the west brine field (fig. 6), other joints and 

fractures are present at least 3,000 feet upstream on Emerson 

Gulf to near the intersection with Woodmancy Road (fig. 7). 

Nearly 75 percent of the 225 joints and fractures mapped in 

the stream channel (fig. SB 1–1) are closed joints, in contrast 

to the joint/fracture relation in the east and west brine fields 

where 24 to 33 percent were closed joints (figs. SB1–3 and 

SB1–4). Reaches of the Emerson Gulf stream also lose water, 

presumably through open fractures on the floor of the channel 

(fig. 7—red polygons). Streamflow measurements were made to 

document losing reaches along Emerson Gulf, although similar 

measurements along the Onondaga Creek channel to the south 

indicated no loss of water along its length. No measurements 

could be made in the east brine field area because of the lack of 

perennial streams draining the east valley wall near the east brine 

field. The heavily fractured nature of the Emerson Gulf bedrock 

channel may be related to the previously noted reverse faulting 

bedrock structure (CS Consulting Engineers, 1992) whose 

orientation roughly strikes parallel to the Emerson Gulf tributary 

valley (fig. 1). A large number of Set III joints (Parker, 1942) are 

also found in the Emerson Gulf valley.

Summary

As a result of the removal of large volumes of halite from 

the brine field by solution mining of the upper halite bed, the 

roofs of the solution cavities caved in soon after solution mining 

began in the Tully Valley. Subsequent solution mining of the 

deeper halite beds caused further bedrock collapse, which was 

followed by land-surface subsidence and the opening of fractures 

in the bedrock walls adjacent to the east and west brine field 

areas. Land-surface subsidence was expressed within the brine 

field area through either widespread bulking subsidence over the 

long history of brine mining, nearly 100 years, or through more 

localized chimney subsidence where rapid sinkhole development 

occurred over the course of hours to days. 

The subsurface movement and sinkhole development 

altered the structural integrity of the bedrock at the valley 

floor/wall margins. The subsidence created by the subsurface 

movement increased the horizontal strain in the bedrock along 

the adjacent valley wall, which led to the opening of pre-existing 

joints in the bedrock along the lower valley walls adjacent to 

each brine field area. On the basis of the spatial association of 

open fractures and adjacent sinkholes, especially in the east brine 

field, most of the subsidence-induced fracture development is 

associated with the rapid structural changes that follow chimneytype sinkhole collapse.

The correlation between open fractures adjacent to 

the brine field areas and joints measured in nearby bedrock 

exposures outside the influence of mining activity shows that the 

development of open fractures follows existing regional closedjoint orientations, some of which are linked to the Alleghanian 

Orogeny. Over the most recent decade, subsurface collapse has 

apparently stabilized, halting the development of additional 

subsidence features at the land surface and the further opening of 

valley-wall fractures. 

By William R. Hackett1

, Gayle C. Gleason2, and William M. Kappel3

1

Department of Geology, University of Vermont, Burlington, VT. 05405. 

william.hackett@uvm.edu

2

Department of Geology, SUNY College at Cortland, Cortland, N.Y. 13045. 

gayle.gleason@cortland.edu

3

U.S. Geological Survey, Ithaca, N.Y. 14850. wkappel@usgs.gov
13

North American Datum of 1983; Universal Tranverse mercator projection, Zone 18N;

Orthoimage base from New York State Office of Cyber and Critical Infrastructure Coordination, Spring 2006.

0 250 500 FEET

0 50 100 METERS

EXPLANATION

Woodmancy

 Road

Emerson Gulf

West 

brine 

field

Emerson

Gulf

This figure

East 

brine

field

Open fracture—line indicates

orientation

Closed joint—line indicates

orientation

Losing reach of Emerson Gulf—

location where water drains into

the bedrock

Solution-mining well

Stream channel—arrow 

indicates direction of flow

Figure 7. Location of open fractures and closed joints within the streambed of Emerson Gulf, west of the west brine field in the Tully 

Valley, Onondaga County, N.Y. (Location shown in figure 1.) 
Figure SB2–1. Seven-inch diameter maple tree growing over an open be

east brine field in the Tully Valley, Onondaga County, N.Y., 2006.

14

The opening of bedrock fractures along the perimeter of 

each brine field was established in reports of The Solvay Process 

Company (1950 and 1960), but the rate of fracture opening 

is not well known. During this study, a maple tree (Acer sp.) 

was found growing over an open fracture above the east brine 

field (fig. SB2–1). The use of dendrochronology (dating the 

growth of trees using tree rings) to determine the rate of fracture 

opening was attempted. Two aspects of the tree were studied: 

(1) the growth rings in the trunk (which can be used to evaluate 

changes in the rate of growth), and (2) the growth rings in the tree 

roots (especially those roots that became exposed to the air as the 

fracture opened and soil fell away from the roots).

The maple tree was almost 7 inches in diameter and was 

determined to be 79 years old in 2006, indicating that it began to 

grow in 1927. An assessment of the tree rings indicated that there 

was no evidence that growth of the tree had been compromised 

by the opening of the fracture (Dr. Thomas Yanosky, U.S. 

Geological Survey—Emeritus, written commun., 2008). In fact, 

the growth rings from 1985 to 2006 were wider than those of the 

previous years indicating healthy and vigorous growth despite the 

tree growing over the open fracture (fig. SB2–1). The outer rings 

of the exposed roots were branch-like in appearance and did not 

display any abrupt change in either ring width or ring anatomy 

that would indicate a rapid excavation of the roots. Rather, the 

exposure of the root to the air as a result of the widening of 

the fracture and the erosion of soil around the root seems to 

have been a gradual process. The outer rings of the roots were 

wide, similar to those of the main trunk, indicating vigorous 

recent growth. 

The wood of maple trees is notorious for the presence of 

“pith flecks” (small pockets of callous tissue that develop when 

boring insects inflict minute damage to the cambium where sap 

flows). Each small fleck is within a single ring, and any one ring 

may have several flecks when examined along the entire ring 

circumference (fig. SB2–2A). When the tree is examined by 

stripping away the bark, one sees a long scar within the outer 

ring created as the beetle bored its way vertically up the cambium 

(fig. SB2–2B). Pith flecks were absent from the innermost rings 

of all the examined roots, but were numerous in the outer growth 

rings. A possible explanation for this phenomenon is that the 

beetles can easily access exposed roots but do not burrow into 

the soil and attack buried roots. Therefore, exposed roots close 

to the main trunk would contain a greater number of pith flecks 

in the outside rings; smaller roots more distant from the main 

trunk would contain fewer pith flecks in the outside rings and no 

pith flecks in the inside rings. This circumstance indicates that as 

the fracture opened under the center of the tree, soil fell into the 

opening fracture and the larger diameter roots close to the trunk 

of the tree became exposed earlier than the smaller diameter roots 

more distant from the tree trunk. The larger, more exposed roots 

were likely attacked periodically by boring beetles, whereas the 

more distant, still-buried roots were not. As the fracture continued 

to open, more distant roots became exposed and accessible to 

pith-boring beetles. 

 Lord of the (Tree) Rings—Explanation of the Growth of a Fracture U
drock fracture above the 

A B

15

 . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . .

Using Tree Rings and Pith Flecks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

The following timeline of fracture development at this location was derived from the treering information:

1927—The tree germinates and begins to grow in soil over the bedrock fracture. The width of the 

fracture in the bedrock is unknown, but it is small enough that it does not affect the initial growth of 

the tree.

1947—Twenty years after the tree began to grow, the fracture has opened enough to cause soil to fall 

into the fracture, allowing the tree roots near the base of the tree to take on a bark-like appearance. 

Beetles begin to create pith flecks in the outer annual ring of the exposed roots.

1975—Forty-eight years after the tree began to grow, more soil had fallen away, exposing more of the 

roots while beetles continue to create pith flecks in the outer annual rings of the exposed roots.

1986—Improved growth as determined by tree-ring analysis of both the trunk and roots are indicative 

of a slowing or cessation of fracture widening.

2006–2008—Tree was removed in 2006 for analysis, and no fracture-width changes were noted at 

this location through 2008. 

In summary, fracture development appears to have been slow at the soil surface when this tree 

germinated, but as it began to grow, bedrock fractures likely began opening on the eastern side of the 

valley sometime in the 1920s (The Solvay Process Company, 1950). Soil had slowly fallen away from 

the base of the tree by the late 1940s, and this particular fracture had continued to widen during the 

following 40–45 years. Currently (2009), the soil may be eroding away from the roots and cascading 

into the fracture opening, but the rate of soil erosion probably is much slower than when the bedrock 

fracture was actively widening.

Figure SB2–2. Example of pith flecks (brown blotches) in a young willow tree, (A) their arrangement in 

individual annual rings from a cross-section of the tree trunk (rings enhanced for clarity) and (B) pith 

channels along the tree trunk with the bark removed.
16

References

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