Geology Reference
In-Depth Information
The Arnold Lava Cave system extends northeast-
erly from Paulina Mountains over 4 miles. In a number
of places the roof has collapsed producing a series of
smaller caves. This long lava channel system formed in
basalt originating from fissures on the flanks of Newbe-
rry caldera. At the southwest end of the Arnold cave
system is the well-known Arnold Ice Cave. Within the
cave, water cascading down the walls freezes into silent
waterfalls. Where the cave intersects the water table,
ice forms. Since the water level is rising, ice now covers
a stairway once in use, so that special climbing equip-
ment is needed to enter the cavern.
Southwest of Arnold Ice Cave, the famous mile-
long Lava River Cave, formerly known as Dillman
Cave, is one of the longest, uncollapsed lava tubes in
Oregon. Leander Dillman, trapper and rancher, discov-
ered the southeast entrance about 1909, but when he
was convicted of "gross immorality" in 1921 the name
was abruptly changed. Entered where the roof has
collapsed, the main passageway of the cave is 5,040 feet
to the lower end which is blocked by sand. Delicate
lava formations, vertically stacked lava tubes, ledges
marking the levels of lava that flowed through the tube,
and unusual sand castles where surface water drained
down through the tube to carve out the sands into a
miniature badlands make the cave of geologic interest.
Lavacicle Cave, south of Millican in Deschutes
County, is best known for its unique spikes of lava
hanging from the ceiling of the tunnel and projecting
up from the cave floor. Discovered in 1959 and named
for these unusual formations, the cave was once filled
to the roof with molten lava. Once the lava had
drained out, the material coating the ceiling of the cave
dripped to the floor forming the pinnacles, called
lavacicles. Lavacicles from the ceiling are only a few
inches long, but those projecting from the floor are 2
to 6 feet in height. Because of the fragile formations,
the cave entrace is barred and permission to enter must
be obtained from the U.S. Forest Service.
On the extreme eastern edge of the Lava
Plains, privately owned Malheur Cave is difficult to
locate. At least one-half of the cave is filled with water
creating a long underground lake where the lava tube
intersects the ground water table. The cave must be
explored by canoe or raft, although the lake waters and
configuration of the tunnel prevent passage after a
certain point.
Crack-in-the-Ground from the south with
Four Craters Lava Field in the back-
ground (photo courtesy of Oregon
Department of Geology and Mineral
Industries).
Crack-in-the-Ground
A narrow northwest-southeast rift in the ground
a few feet wide, 2 miles long, and up to 70 feet deep in
places has remained open for several thousand years.
Located in Lake County between prehistoric Christmas
Lake to the south and the Four Craters lava field to
This narrow, two mile-long crack in Lake County
opened in layers of lava when a block beneath the
flow dropped down. (after Peterson and Groh, 1964)
