Images courtesy of Dr. Jack Ridge at Tufts University unless noted otherwise
Copyright © 2011 Environmental Literacy and Inquiry Working Group at Lehigh
University

A varve is composed of
an annual sediment layer
taken from a core.

Like the annual tree ring
layers (left), we are
interested in the annual
varve thickness (right).

The Summer Layer:
◦ Lighter in color
◦ Sandy or silty in texture
Tree ring (NOAA
Paleoclimate)

The Winter Layer:
◦ Darker in color
◦ Is often high in clay content
and fine sediment
A picture of a varve core
(http://ase.tufts.edu/geology/varv
es/default.asp)
Dr. Ridge
taking a core
with students.
(http://ase.tufts
.edu/geology/v
arves/default.a
sp)

Varves can be used as a climate proxy due to the
variability in their annual thickness.

Thicker varves indicate warmer climate years.

Thinner varves indicate colder climate years.

Changes in varve thickness can be plotted against
time to determine climate variability.

One varve year (summer
and winter) is contained
between the yellow
arrows.

The variability in varve
thickness can be used as
a climate proxy.

A long term climate record
can be assembled using
changes in varve
thicknesses in a core.
Cool Year
Warm Year
A sample varve that is typical of the New England area
(http://ase.tufts.edu/geology/varves/default.asp)

A warmer climate
more meltwater from the glacier
thicker varve layers. (More Sediment)

A colder climate
less meltwater from the glacier
thinner varve layers. (Less Sediment)

Water from the melting glacier carries
sediment into a lake basin.

In the picture to the right, we can
observe a melting glacier
(2003-2005).
Much of the Northeastern United States was
covered by ice at one time.
The red line
indicates the
furthest
extent of the
glaciers.
Other lines
indicate
landforms
where the
glacier
paused in its
retreat.
Bethlehem, PA
Map of NE deglaciation
(http://ase.tufts.edu/geology/varves/default.asp)


Glacial Period- A
cool period in
which glaciers
advance.
Interglacial
Period- A warm
period in which
glaciers retreat.
Glacier
http://earthobservatory.nasa.gov/IOTD/view.php?id=40962
Keep in mind that eventually the ice will
retreat away from the lake during a warm
period. This means that less sediment will
be deposited into the lake.



Lake varves can only be found in regions that
were affected by glaciers.
The varves for this activity come from
Dummerston, VT.
Scientists study varves in this location
because there used to be a large glacial lake
where these lake varves could form.
Finding Lake Varves/Methods
• Varves can be
measured in section
from bottom to top
(right)
Continuous Deep Drilling
Truck
Multiple drill bits that each
contain a varve core
A varve core packed in plastic
tubing for transport to the lab
and analysis
• Small sections of a
varve chronology
close to the surface
can be cored.
• Cores can also be
retrieved using large
mechanized drilling
system (pictures to the
left)
A student measuring a varve in
section from bottom to top.
(http://ase.tufts.edu/geology/varv
es/default.asp)
Once back in lab cores can
be photographed and the
thickness of each varve
layer can be measured.

Each group will measure varve thicknesses within
a piece of a core section. This section represents
a part of a long term record (~300 years).

Measurements will be recorded in a data table and
then plotted on the appropriate graph paper.

Graphed data will be aligned to form a
paleoclimate reconstruction using lake varve
measurements.
5695
5693
1. Measure
the width of
each varve
layer (cm)
5690
5685
2. Record the
data in the
measurement
table to the
right.
New England
Varve Year
Measurement
(cm)
5685
2.71
5686
2.09
5687
3.00
5688
2.74
5689
1.55
5690
0.63
5691
1.57
5692
1.75
5693
3.13
5694
2.51
5695
0.93
Core1 (Varve Years 5685 to 5714)
4.0
3.5
Varve Thickness cm
3.0
Warming
Trend
2.5
2.0
1.5
1.0
Cooling
Trend
0.5
0.0
5685
5690
5695
5700
5705
5710
New England Varve Year
3. Plot the points from the previous table onto the
associated graph and connect the dots.

Keep in mind that glaciers advance and retreat.
◦ This greatly influences the amount of sediment deposited
into a glacial lake.

As glaciers retreat the amount of sediment being
deposited into a glacial lake decreases.

It is sometimes difficult to accurately interpret a
varve record.
◦ Keep this in mind as you interpret this paleoclimate
record.