Skip to main content
U.S. flag

An official website of the United States government

Borehole Extensometer

By Virginia and West Virginia Water Science Center
A borehole extensometer. A pipe extends through an aquifer (subject to compaction) down to bedrock (subject to isostacy).
Original Thumbnail Medium

Detailed Description

A borehole extensometer is an instrument that measures vertical land motion caused by changes in aquifer thickness. A borehole is drilled through the entirety of an aquifer system and the steel pipe is anchored at the base to the basement rock. Aquifer compaction is measured by the change in the length of the extensometer pipe which protrudes above the ground surface.

Extensometers measure only changes in aquifer thickness, not other deep-earth causes of subsidence such as glacial isostatic adjustment.

Based on the USGS extensometer at Nansemond, Virginia (USGS 365337076251606 59D 39).

Sources/Usage

Public Domain.

Related

link
Close up photo of the nansemond extensometer, showing the counter-weight, fulcrum arm, and pressure gauge.

The Virginia Extensometer Network

Borehole extensometers are instruments that monitor land subsidence caused by aquifer compaction. They provide precise, high-resolution measurements of changes in aquifer-system thickness. These changes in aquifer-system thickness contribute to vertical land motion (VLM) across the Virginia Coastal Plain, and are driven primarily by groundwater level decline due to human water usage. The Virginia...
By
Chesapeake Bay Activities, Virginia and West Virginia Water Science Center
link

The Virginia Extensometer Network

Borehole extensometers are instruments that monitor land subsidence caused by aquifer compaction. They provide precise, high-resolution measurements of changes in aquifer-system thickness. These changes in aquifer-system thickness contribute to vertical land motion (VLM) across the Virginia Coastal Plain, and are driven primarily by groundwater level decline due to human water usage. The Virginia...
Learn More

Subsidence Infographics

Comparison of the depths of four Virginia extensometers to the heights of some of the USA's tallest buildings.
Virginia Extensometers Depth Comparison
Virginia Extensometers Depth Comparison
Methods of Measuring Land Motion, including extensometers, Monitoring wells, InSAR, and GNSS Surveys
Methods of Measuring Land Motion
Methods of Measuring Land Motion
Illustration of the geology of the Virginia Coastal Plain
Virginia Coastal Plain Aquifer Geology
Virginia Coastal Plain Aquifer Geology
2d and 3d representations of the aquifers of the Virginia Coastal Plain
Virginia Coastal Plain Aquifer systems
Virginia Coastal Plain Aquifer systems
A borehole extensometer. A pipe extends through an aquifer (subject to compaction) down to bedrock (subject to isostacy).
Borehole Extensometer
Borehole Extensometer
An extensometer measures aquifer compaction. Reduction in aquifer thickness causes more of the steel pipe to protrude.
Extensometer - Aquifer Compaction
Extensometer - Aquifer Compaction
Infographic showing parts of an extensometer, including fulcrum arm, counterweight, instruments, instrument table, & borehole
Borehole Extensometer
Borehole Extensometer
An infographic showing how the weight of ice sheets deforms the underlying crust and can lead to isostatic adjustment.
Glacial Isostatic Adjustment
Glacial Isostatic Adjustment
An animated infographic showing how groundwater depletion in a confined aquifer can lead to aquifer compaction and subsidence
Aquifer compaction and land subsidence
Aquifer compaction and land subsidence

Virginia Extensometer Network

Filter Total Items: 27
Surface instrumentation for the West Point extensometer, including instrument table and fulcrum arm.
The USGS West Point Extensometer
The USGS West Point Extensometer
The building housing the West Point extensometer. The actual extensometer can be seen inside through the open doors.
The extensometer shed at West Point.
The extensometer shed at West Point.
A USGS technician standing on a ladder works on the instrument table above the West Point Extensometer.
Installing GNSS at the West Point Subsidence Superstation
Installing GNSS at the West Point Subsidence Superstation
View of the above-ground portion of the West Point extensometer, including the protruding section of pipe &fulcrum arm.
The West Point Extensometer
The West Point Extensometer
Two USGS scientists balance the fulcrum arm on the West Point extensometer.
Balancing the West Point Extensometer
Balancing the West Point Extensometer
A USGS drilling rig
Drilling for the West Point Borehole Extensometer
Drilling for the West Point Borehole Extensometer
A USGS geologist monitors the sediments coming up out of a drill rig
Geologists Monitoring Sediment during West Point Extensometer Drilling
Geologists Monitoring Sediment during West Point Extensometer Drilling
A drilling rig lifting a long length of pipe in preparation for feeding it into the ground
Drilling Rig Feeding Pipe into the Borehole for the West Point Extensometer
Drilling Rig Feeding Pipe into the Borehole for the West Point Extensometer
Inside the Nansemond extensometer shed. Above the extensometer sits the green and yellow instrument table.
Nansemond Borehole Extensometer
Nansemond Borehole Extensometer
Close up photo of the nansemond extensometer, showing the counter-weight, fulcrum arm, and pressure gauge.
The USGS Nansemond Extensometer
The USGS Nansemond Extensometer
Virginia Extensometer Drilling Site
Virginia Extensometer Drilling Site
Virginia Extensometer Drilling Site
The USGS Nansemond drilling site.
USGS Nansemond drilling site.
USGS Nansemond drilling site.
The USGS Nansemond research station.
The USGS Nansemond research station.
The USGS Nansemond research station.
The USGS Nansemond pipe extensometer with a total depth of 1,960 feet.
The USGS Nansemond pipe extensometer
The USGS Nansemond pipe extensometer
The USGS Nansemond pipe extensometer.
The USGS Nansemond pipe extensometer.
The USGS Nansemond pipe extensometer.
The USGS Nansemond research station.
The USGS Nansemond research station
The USGS Nansemond research station
An analog dial gage (left) and a digital linear potentiometer (right with blue barrel).
Analog dial gage (left) and a digital linear potentiometer (right)
Analog dial gage (left) and a digital linear potentiometer (right)
Pivot block where the USGS Nansemond extensometer connects to the fulcrum arm.
USGS Nansemond extensometer Pivot Block.
USGS Nansemond extensometer Pivot Block.
Installing the linear potentiometer on the USGS Nansemond extensometer.
Installing the linear potentiometer on the USGS Nansemond extensometer
Installing the linear potentiometer on the USGS Nansemond extensometer
Connecting drill stem to the top head drive on the USGS Research Drilling program’s rig.
Connecting drill stem to the top head drive on the USGS Research Rig
Connecting drill stem to the top head drive on the USGS Research Rig
The USGS Franklin pipe extensometer with a total depth of 860 feet.
The USGS Franklin pipe extensometer with a total depth of 860 feet.
The USGS Franklin pipe extensometer with a total depth of 860 feet.

Related

link
Close up photo of the nansemond extensometer, showing the counter-weight, fulcrum arm, and pressure gauge.

The Virginia Extensometer Network

Borehole extensometers are instruments that monitor land subsidence caused by aquifer compaction. They provide precise, high-resolution measurements of changes in aquifer-system thickness. These changes in aquifer-system thickness contribute to vertical land motion (VLM) across the Virginia Coastal Plain, and are driven primarily by groundwater level decline due to human water usage. The Virginia...
By
Chesapeake Bay Activities, Virginia and West Virginia Water Science Center
link

The Virginia Extensometer Network

Borehole extensometers are instruments that monitor land subsidence caused by aquifer compaction. They provide precise, high-resolution measurements of changes in aquifer-system thickness. These changes in aquifer-system thickness contribute to vertical land motion (VLM) across the Virginia Coastal Plain, and are driven primarily by groundwater level decline due to human water usage. The Virginia...
Learn More

Subsidence Infographics

Comparison of the depths of four Virginia extensometers to the heights of some of the USA's tallest buildings.
Virginia Extensometers Depth Comparison
Virginia Extensometers Depth Comparison
Methods of Measuring Land Motion, including extensometers, Monitoring wells, InSAR, and GNSS Surveys
Methods of Measuring Land Motion
Methods of Measuring Land Motion
Illustration of the geology of the Virginia Coastal Plain
Virginia Coastal Plain Aquifer Geology
Virginia Coastal Plain Aquifer Geology
2d and 3d representations of the aquifers of the Virginia Coastal Plain
Virginia Coastal Plain Aquifer systems
Virginia Coastal Plain Aquifer systems
A borehole extensometer. A pipe extends through an aquifer (subject to compaction) down to bedrock (subject to isostacy).
Borehole Extensometer
Borehole Extensometer
An extensometer measures aquifer compaction. Reduction in aquifer thickness causes more of the steel pipe to protrude.
Extensometer - Aquifer Compaction
Extensometer - Aquifer Compaction
Infographic showing parts of an extensometer, including fulcrum arm, counterweight, instruments, instrument table, & borehole
Borehole Extensometer
Borehole Extensometer
An infographic showing how the weight of ice sheets deforms the underlying crust and can lead to isostatic adjustment.
Glacial Isostatic Adjustment
Glacial Isostatic Adjustment
An animated infographic showing how groundwater depletion in a confined aquifer can lead to aquifer compaction and subsidence
Aquifer compaction and land subsidence
Aquifer compaction and land subsidence

Virginia Extensometer Network

Filter Total Items: 27
Surface instrumentation for the West Point extensometer, including instrument table and fulcrum arm.
The USGS West Point Extensometer
The USGS West Point Extensometer
The building housing the West Point extensometer. The actual extensometer can be seen inside through the open doors.
The extensometer shed at West Point.
The extensometer shed at West Point.
A USGS technician standing on a ladder works on the instrument table above the West Point Extensometer.
Installing GNSS at the West Point Subsidence Superstation
Installing GNSS at the West Point Subsidence Superstation
View of the above-ground portion of the West Point extensometer, including the protruding section of pipe &fulcrum arm.
The West Point Extensometer
The West Point Extensometer
Two USGS scientists balance the fulcrum arm on the West Point extensometer.
Balancing the West Point Extensometer
Balancing the West Point Extensometer
A USGS drilling rig
Drilling for the West Point Borehole Extensometer
Drilling for the West Point Borehole Extensometer
A USGS geologist monitors the sediments coming up out of a drill rig
Geologists Monitoring Sediment during West Point Extensometer Drilling
Geologists Monitoring Sediment during West Point Extensometer Drilling
A drilling rig lifting a long length of pipe in preparation for feeding it into the ground
Drilling Rig Feeding Pipe into the Borehole for the West Point Extensometer
Drilling Rig Feeding Pipe into the Borehole for the West Point Extensometer
Inside the Nansemond extensometer shed. Above the extensometer sits the green and yellow instrument table.
Nansemond Borehole Extensometer
Nansemond Borehole Extensometer
Close up photo of the nansemond extensometer, showing the counter-weight, fulcrum arm, and pressure gauge.
The USGS Nansemond Extensometer
The USGS Nansemond Extensometer
Virginia Extensometer Drilling Site
Virginia Extensometer Drilling Site
Virginia Extensometer Drilling Site
The USGS Nansemond drilling site.
USGS Nansemond drilling site.
USGS Nansemond drilling site.
The USGS Nansemond research station.
The USGS Nansemond research station.
The USGS Nansemond research station.
The USGS Nansemond pipe extensometer with a total depth of 1,960 feet.
The USGS Nansemond pipe extensometer
The USGS Nansemond pipe extensometer
The USGS Nansemond pipe extensometer.
The USGS Nansemond pipe extensometer.
The USGS Nansemond pipe extensometer.
The USGS Nansemond research station.
The USGS Nansemond research station
The USGS Nansemond research station
An analog dial gage (left) and a digital linear potentiometer (right with blue barrel).
Analog dial gage (left) and a digital linear potentiometer (right)
Analog dial gage (left) and a digital linear potentiometer (right)
Pivot block where the USGS Nansemond extensometer connects to the fulcrum arm.
USGS Nansemond extensometer Pivot Block.
USGS Nansemond extensometer Pivot Block.
Installing the linear potentiometer on the USGS Nansemond extensometer.
Installing the linear potentiometer on the USGS Nansemond extensometer
Installing the linear potentiometer on the USGS Nansemond extensometer
Connecting drill stem to the top head drive on the USGS Research Drilling program’s rig.
Connecting drill stem to the top head drive on the USGS Research Rig
Connecting drill stem to the top head drive on the USGS Research Rig
The USGS Franklin pipe extensometer with a total depth of 860 feet.
The USGS Franklin pipe extensometer with a total depth of 860 feet.
The USGS Franklin pipe extensometer with a total depth of 860 feet.
Was this page helpful?