This is the fifth in a series of eight earthcaches being
developed at major points of interest in
Newberry National Volcanic Monument in cooperation with the
staff of the Deschutes National Forest. Lava River Cave is closed
to all entry from November 1 to April 30 to protect hibernating
bats. For the remainder of the year (May 1 to October 31) the cave
is open to the public. The cave entrance is staffed from
approximately Memorial Day to Labor Day. No logs for this
earthcache will be accepted from November 1 to April 30.
To log this cache you will need to go more than half way through
the cave and you will need a tape measure. Please post a photo
taken in the cave. There are three interpretive signs in the cave,
e-mail me the "sign titles" and "width of the cave" at each of the
signs (to the nearest foot).
While doing this earthcache you may also be able to collect the
necessary information to claim several waymarks in the area.
Lava River Cave is an excellent
example of a lava tube and is the longest continuous tube in
Oregon.
During long-lived eruptions flowing lava
becomes channelized into a few main streams. Overflows of lava
from these streams solidify quickly and plaster on to the
channel walls, building natural walls that allow the level of
the lava to be raised. Lava streams that flow steadily in a
confined channel for many hours to days may develop a solid
crust or roof and thus change gradually into streams within
lava tubes. If molten rock (magma) stops rising to the surface
at the source, the still-molten lava moving beneath the
crusted-over top of a lava flow can continue to drain downhill
and may ultimately leave an open lava tube cave. Because the
walls and roofs of such tubes are good thermal insulators,
lava flowing through them can remain hot and fluid much longer
than surface flows. Tube-fed lava can be transported for great
distances from the eruption sites.
Newberry Volcano has been the source of numerous high volume
tube-fed lava flows that have flowed northward well beyond Bend.
These high volume flows generally come from small spatter/fissure
vents. These vents were typically low on the flanks of Newberry.
The highest elevation vent was in the area of Mokst Butte but it
has been buried by Mokst Butte and its flows. The eruption from
this vent occurred about 80,000 years ago and resulted in a flow
which nearly reaches Redmond and underlies much of Bend. Lava River
Cave was a major tube that carried the flow westward to the
Deschutes River.
