Washington Geology, Volume 28, No. 3. May 2001.
by: Wendy Gerstel
Have you ever looked at a stone wall and wondered where all the different rocks came from and what story each might tell? Some stone walls are made of angular rocks, probably mined from a quarry. Others are made of rounded stones. Observing the differences in shape, size, color, mineralogy, and other characteristics of the stones in a wall can tell us a lot about the history of the stones and of the wall. Stone wall builders usually take advantage of the most readily available and, of course, best looking materials. Walls can be used to support a building or to hold back a hillside or as decorative landscaping (Fig. 1). Here in western Washington, many of the walls, such as those facing the buildings on the Capital Campus, are built of angular stones quarried from the Wilkeson Sandstone near Tenino. In eastern Washington, many walls are made of basalt because of the abundance of that rock type there. A wide variety of metamorphic rocks can be found in the walls of north-central Washington.
In the Puget Sound area, we have an abundance of rounded stones of all sizes, carried here by glaciers that covered the area about 13,000 years ago. These stones have been tumbled, scraped, rolled, smoothed, and sculpted by the ice and its meltwater streams. The more rounded the stones, the longer they were rolled in streams. If they are faceted, that is, have rounded but distinct faces, they were probably deposited directly by the ice.
Rounded stones do not fit snugly against other stones in a wall and usually need mortar to hold them together. In New England and other areas on glacial deposits, however, farmers build walls with the stones cleared from their fields. Careful placement of the stones and annual spring maintenance preserve many miles of these walls built without any mortar. In Figure 2, the larger stones are at the bottom so they were probably put in place by hand. The smaller ones could be lifted, so were used in the upper layers.
This lesson will teach observation, analytic, and note-taking skills. It will encourage the observer to think about geology, history, transportation, engineering, and social sciences - and other aspects of wall building left to the creativity of the participants.
Questions
Find your own stone wall and answer the following questions:
1.
What
do
you
notice
about
the
shape
of
the
individual
stones?
Are
all
of
them
rounded?
Are
any
of
them
angular?
Are
some
of
them
faceted?
Was
it
built
for
decoration,
to
protect
a
garden,
or
to
support
a
structure?
2.
Did
the
wall
builders
use
Mortar?
Why
is
this
important?
Could
the
wall
have
been
built
without
it?
What
is
the
mortar
made
from?
3.
What
can
you
say
about
the
color
of
the
stones?
Look
closely.
Do
you
recognize
any
of
them
from
Washington
State?
From
Canada?
From
Idaho?
What
do
you
notice
about
the
mineralogy
-
the
individual
crystals
within
a
stone?
4.
How
did
the
stones
get
here?
Are
they
local?
Were
they
transported
by
glaciers
or
streams,
by
trucks
or
trains?
5.
Note
the
size
and
relative
placement
of
the
stones
in
the
wall.
Is
this
important?
Does
it
tell
you
anything
about
how
the
wall
was
built
-
by
humans
or
machine?
6.
What
can
you
say
about
the
age
of
the
wall?
What
do
the
surroundings
(the
building,
the
landscaping,
the
rock
source,
etc.)
tell
you?
What
condition
is
the
wall
in?
Discussion
1.
How
does
geology
control/affect
the
availability
of
building
materials
and
how
they
are
used?
And
how
does
access
to
and
transportation
of
the
materials
affect
their
use?
2.
What
can
you
say
about
the
age
of
a
wall
and
the
use
of
particular
materials?
(How
far
they
were
transported?
How
they
were
put
into
place,
etc.?)
3.
How
might
the
function
of
a
wall
have
changed
through
human
history
in
an
area?
In
different
areas,
climates,
cultures?
4.
What
are
the
advantages/disadvantages
of
stone
walls?
As
compared
to
wooden
fences?
(Costs,
resource
availability,
other?).
5.
What
might
cause
a
wall
to
degrade
or
weather
(chemical
and
mechanical
[wind
and
water]
break
down)?
Which
would
be
more
susceptible
to
weathering,
a
rounded
wall
or
a
wall
of
blocky,
tight-fitting
stones?
References
Articles
Guide to Geologic, Mineral, Fossil, and Mining History Displays in Washington, by David A. Knoblach: Washington Geology, v. 22, no. 4, p. 11-17, 1994.
The H.P. Scheel Family - A History in Stone, by David A. Knoblach: Washington Geology, v. 27, no. 1, p. 18, 1999.
Washington's Stone Industry - A History, by David A. Knoblach: Washington Geology, v. 21, no. 4, p. 2-17, 1993.
Books
Rocks and Minerals and the Stories They Tell, by Robert Irving, illustrated by Ida Scheib: Knopf, 175p. 1956.
Rocks and Minerals - Student Activity Book, by the National Science Resources Center, Smithsonian Institution, National Academy of Science: Carolina Biological Supply Co., 153 p., 1994.
Sermons in Stone - The Stone Walls of New England & New York, by Susan Allport with ink drawings by David Howell: W.W. Norton & Co. 205p. 1990.
Time worships a well-built wall, for a wall's stones can wend through silent woods with an eerie eloquence, suggesting the lives and labours of settlers long gone. As Susan Allport demonstrates in this charming book, the stone walls of New England and New York speak with the voices of Native Americans and Yankee farmers, of slaves, servants, and children, evoking the past from the elemental geological struggles of the Ice Age through the fencing dilemmas of neighbors in the 19th century. Allport's scaling of these humble but pervasive walls - who built them? When? Why? How? - is a narrative of fascinating and offbeat attention to the enduring tracks of the past [downloaded January 1, 2001, from http://www.commonreader.com/cgi-bin/rbox/ido.cgi?7248].
Stone
Wall
Secrets
by
Kristine
and
Robert
Thorson:
Tilbury
House
Publishers,
40
p.
1998.
[grades
3-6]
Stone
Wall
Secrets
-
Exploring
Geology
in
the
Classroom
(Teachers'
Guide),
by
Ruth
Deike:
Tilbury
House
Publishers,
80
p.
1998.
Website
Discovery.com has lessons, weblinks, and vocabulary at http://school.discovery.com/lessonplans/programs/rocks/index.html.
Essential science learning benchmarks/objectives
1.1
Uses
Properties
to
identify,
describe
and
catergorize
landforms.
3.2
Understands
that
science
and
technology
are
human
endeavors,
interrelated
to
each
other,
to
society.
And
to
the
workplace.
Grade levels
Grades
2-6,
answer
questions
1-3.
Grades
7-12,
answer
questions
1-6.
Subjects
Earth
science
Geography
Social
science
Mechanics/engineering
Concepts
Interpreting geologic origin of building materials and methods of transport and use.
Skills
Observations; identifying relationships of rocks to where they originated; hypothesizing rock transport.
Time needed
30-45 minutes (more if field trip)
"The small stones which fill up the crevices have almost as much to do with making the fair and firm wall as the great rocks, so wise use of spare moments contributes not a little to the building up in good proportions a man's mind." (Edwin Paxton Hood)
Lesson created by:
Wendy
Gerstel,
Washington
Division
of
Geology
and
Earth
Resources,
P.O.
Box
47007,
Olympia,
WA
98405-7007
e-mail: geology@wadnr.gov
Permission is granted to photocopy these lessons. Copyright has been waived.