NEWBERRY VOLCANO
Newberry Volcano in central
Oregon is part of the Cascade Range of America's Pacific Northwest. The
presence of Newberry Volcano, like the other Cascade volcanoes, is the result
of the Juan de Fuca Plate subducting beneath the North American Plate along
offshore Oregon & Washington State. Newberry Volcano experienced a
large eruption and has collapsed, forming a large caldera, now partially
occupied by two lakes (Paulina Lake & East Lake).
(Satellite photo provided by
TerraMetrics & DigitalGlobe & Google Earth)
LAVA BUTTE
Lava Butte is an obvious
& decent-sized cinder cone on the western side of Rt. 97, about 10 miles
SSW of Bend, central Oregon, USA. It is one several volcanic features
associated with a NNW-SSE trending fracture system extending from Newberry
Volcano to the south.
Basalt & vesicular
basalt aa lava flows extend to the west & northwest from Lava Butte.
These were erupted in about 5075 B.C. (~early Holocene).
Lava Butte Cinder Cone is
the rounded structure near the lower right corner. The brown sheet
extending toward the center & upper right of photo are the ~5075 B.C. lava
flows. (Satellite
photo provided by TerraMetrics & DigitalGlobe & Google Earth)
Looking N.
Lava breach on the southern
side of the Lava Butte Cinder Cone. Lava erupted from a fissure developed
in the flanks of the cinder cone, rather than from a vent at the top.
Looking ~WNW.
Looking ~W.
~5075 B.C. basaltic aa lava
flow.
Basalt & vesicular
basalt lava, ~5075 B.C. eruption of Lava Butte Cinder Cone.
Lava Cast Forest
Fossils are only common in
sedimentary rocks. They are scarce in metamorphics, and are exceedingly
rare in igneous rocks. Famous examples of fossils in igneous rocks
include a rhinoceros in the Columbia Plateau Flood Basalts (Blue Lake,
Washington State) and some trees in the basalt lavas of the Hawaii Hotspot.
Another spectacular place
for seeing fossils in igneous rocks is Lava Cast Forest, central Oregon.
Many upright & horizontal tree molds are preserved in the Lava Cast
Forest Flow (an aa lava flow consisting principally of vesicular basalt and
some scoriaceous basalt), which erupted about 5260 B.C. from a fissure ~7 miles
north-northwest of Newberry Volcano. [these tree molds really aren't
fossils, since they aren't >10,000 years old, but that's a minor quibble]
Location: area of 43° 48' 54" North, 121° 17' 11"
West.
Some of the tree molds are
suspiciously rounded, and resemble large drill holes. The trees
represented by the molds were likely ponderosa pines, which are still common in
central Oregon. Only occasional carbonized traces of the original trees
remain. During the original eruption, lava piled up against the upstream
side of the trees - these lava pile-ups are still evident, and the upstream
lava flow direction is readily discernible.
Basaltic aa lava of the Lava
Cast Forest Flow (erupted ~5260 B.C.).
Looking down into a vertical
tree mold in the Lava Cast Forest Flow.
Another vertical tree mold,
with a lava pile-up at the back (indicating the lava flow's upstream direction).
A horizontal tree mold in
the Lava Cast Forest Flow.
View of the inside of a
horizontal tree mold.
This gives a sense of scale
for one of the larger upright tree molds. This one has a particularly
sizable lava pile-up on the upstream side.
A modern ponderosa pine
living between two lobes of the Lava Cast Forest Flow.
BIG OBSIDIAN
FLOW
Words and pictures really
don't do justice to the Big Obsidian Flow of Newberry Volcano in central
Oregon, USA. There's nothing quite like walking on a gigantic pile of
black volcanic glass. Erupted in ~700 A.D., this lava flow in Newberry
Volcano's caldera is a jumbled mixture of rhyolitic obsidian, rhyolite pumice,
vesicular rhyolite, and rhyolite. The obsidian is its most appealing
feature, and one has to mind carefully the placement of feet and hands because
exceedingly sharp broken glass is everywhere.
Location: southern side of Rt. 21 in
the Newberry Volcano caldera, just southeast of Paulina Lake, southern
Deschutes County, central Oregon, USA. Area of 43° 42' 15" North,
121° 14' 06" West.
(Satellite photo provided by
DigitalGlobe & Google Earth)
Lava flow front of the Big
Obsidian Flow (~700 A.D.). The body of water in the foreground is Lost
Lake. Looking east.
Flow top of the Big Obsidian
Flow.
Large, sharp-edged boulder
of flow-banded rhyolitic obsidian.
Making a throne of sharp,
irregular obsidian boulders is tricky, but black rock that has been warmed by
the Sun is welcome on a chilly, windy day.
World-class piece of
rhyolitic obsidian.
I didn't keep it (this is a park).
Lifting a boulder of pumice.
Nice vesiculation on a piece
of partially pumiceous rhyolite.
Interesting obsidian-pumice
flow banding. This is somewhat the equivalent of flame structures in
turbidites. A piece of obisidian (black chunk at right-center) has been
picked up and moved around, drawing thin strands of pumiceous & non-pumiceous
glass into a convoluted, folded pattern.