Geology Reference
In-Depth Information
In Lava River Cave south of Bend the lava remained molten while the roof and sides solidified. Flowing
out, the lava left flow lines, benches, and a keyhole-shape to the sides of the tunnel (photo courtesy of
Oregon State Highway Department).
Lava Caves
follow the twisting pathway of an ancient stream
A number of caves and long cavern systems exist
channel cut into the surface and filled in by lava. As
in the Bend area as a result of volcanism which took
the lava smoothed out the older topography, the
place during the Pliocene and Pleistocene throughout
thicker flows along stream channels remained liquid to
the western High Lava Plains. Tubes and tunnels in
drain out while the roof hardened. After the lava tube
basalt occur as molten lava cools to form a solid crust
has formed, weathering processes attack the roof,
on the surface even as the hot lava stream continues to
leading to collapse, and producing cave openings,
run out deep in the flow. As volcanic activity producing
Historically lava caves were used for shelter by
the lava ceases, the tube is drained leaving the cave or
Indians and early settlers. Eastern Oregon ranchers
cavern. Tubes usually form when lava is thick and
often kept meat chilled in caves which maintain a
syrupy, and caves are most common in pahoehoe flows.
temperature of 40 degrees Fahrenheit year round. In
Wide lava sheets often have several tubes within the
the early part of the century, large blocks of ice were
flow, some of which may be interconnected by lateral
cut from Arnold Ice Cave to supply the nearby commu-
passages. Pahoehoe lava, flowing through a narrow
nity of Bend on a commercial basis. One unusual
valley, will ordinarily produce only a single tunnel or a
advantage settlers found for the caves near Bend was as
series of tubes which are stacked up over each other.
a place to brew whiskey. Federal agents conducting
The pathway of lava caves are variously straight
monthly raids, as the one in January, 1921, confiscated
to meandering. Straight caves follow old fault and
2 stills, 3 quarts of whiskey, and several barrels of corn
fracture patterns. More often, however, lava caves
mash. Once raided, the caverns were sealed.
