Mima mounds were first described in Washington State, but can be
found in many areas throughout the United States and around the
world. Mysterious and beautiful, there have been many
theories about there origin.
Mima Mound distribution in the U.S.
Various theories range from Native American burial mounds, to
the somewhat extreme "giant gophers". For whatever reason,
they are still fun to look at, and in some areas, to explore.
The Fort Ord Public Lands however, has a strict off trail
policy. Please stay on the trail. The
coordinates for this Earthcache will take you to an interpretive
board that explains the Mima Mounds of Fort Ord.
Fort Ord Mima Mounds from Google Earth
The Mystery of Mima Mounds
The formation of mima mounds is still a mystery, but many
theories have been put forth. The association of the nearby
Vernal Pools in the Fort Ord area is one plausible explanation for
this particular group of mima mounds, but other explanations cannot
be discounted. The interpretive board at the coordinates
above lists the possible explanations, or perhaps a combination of
these explanations is the answer.
- Ground cracking and heaving during the colder Ice Age
conditions.
- Expansion and contraction of clay during wet and dry weather
cycles.
- Wave action of the higher sea level when the area was
submerged.
- Differential settling of lagoon sediments.
- Mound forming activity of burrowing rodents.
- Domes of methane gas plumes from underlying boggy soils.
- A combination of the above processes.
In addition, experiments have been done to test the possibility
of seismic action, using a piece of plywood covered with loose
soil. Indeed, the vibration of the board did produce an
effect on the loose soil that does resemble the same arrangement of
mounds that you would see here on Fort Ord. This was a theory
put forth by A Berg in the 1990's.
In 2004, VOILE, Toni and ORNDORFF, Richard L., submitted an
Abstract for the GSA Conference in Denver, CO which analyzed
various soil samples from a mima mound area in Western Washington
State. Their conclusions seemed to support the seismic theory
of formation:
"Consolidation testing demonstrated that Mima mound soil
exhibits a much looser structure than Palouse soil. These
characteristics of Mima mound soils may be most consistent with the
seismic hypothesis for Mima mound formation."
Still, the Indian Burial Mound, or even the Paul Bunyan Theory,
are fun to think about. Maybe you can come up with your own
theory and put forth your proposal in your Log Entry.
Logging Requirement:
At the coordinates above, you will find an interpretive board
that was installed back in the 1970's by the Army Corp of
Engineers, which undertook an environmental assessment of Fort
Ord. You can get a pretty good view from this location of the
field of mima mounds of Fort Ord.
Mima mounds can vary in size, depending on the area. In
one Mima Mound Preserve in Washington State, the mounds are nearly
eight feet high! What do guess would be the average
height of the Fort Ord Mima Mounds?
Email me your answers by clicking on the email link on my
Profile.
Mima Mounds and Similar Landforms
Mounds
of Mystery
ENGINEERING PROPERTIES OF MIMA MOUND SOILS FROM TURNBULL NATIONAL
WILDLIFE REFUGE
Dear Treasure Cacher:
The Bureau of Land Management (BLM) welcomes “treasure cachers”
to the Fort Ord Public Lands and we hope that enjoy your visit to
this ecologically unique and diverse area. At Fort Ord, the
BLM is carefully managing this activity to ensure that your visit
is safe and enjoyable, and that the sensitive natural, cultural,
and historic resources are protected for current and future
generations. The cache you are searching for has likely been
posted on one of the many “treasure cache” related websites such as
geocaching.com, letterboxing.org, atlasquest.com, etc. When
looking for this cache, we ask that you take note of our public use
restrictions on the land that include:
- Please use only trails that are signed open and shown on our
Fort Ord Public Lands Trail Maps. Cross-country travel, use of
unsigned trails and bushwhacking is not allowed.
- Please limit your cache searches to daylight hours. The
BLM lands are closed from ½ hour after sunset to ½ hour before
sunrise.
- Enjoy your cache hunting on foot, hoof or bicycle wheel because
vehicle use (including motorcycles, ATV’s and four-wheel drives)
are not allowed on the BLM road and trail systems.
- When considering a treasure to leave, please remember that this
is a family-friendly sport and never leave anything pornographic,
offensive, or flammable. Please never leave food
items.
Caches that have been approved by the BLM will never be more
than 20 feet from one our designated trails or roads, so save the
effort looking far off trail. Also, be sure to avoid tampering
with anything that is not within a clear container because there is
still a chance that dangerous military artifacts may be in the
area. Always obey signs that indicate closed areas that
include habitat restoration sites and dangerous munitions
sites. And remember, the lands you visit are home to several
species of rare and endangered plants and animals, so please tread
lightly and respect the natural environment.
If you have any questions about your visit to this area, feel
free to contact the BLM at (831)394-8314 or
(831)630-5000.