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Hawaii Volcanoes National Park, on the Big Island of Hawaii
Here, we visit the great active caldera of Kilauea volcano. Then, in the next slide show,
we walk to the glowing lava of Kilauea’s east rift, and see the earth turning inside out.
All photos by R., C., J., or K. Alley, except two from the United States Geological Survey
(USGS), and so labeled.
GEOSC 10: Unit 3: Plate Tectonics II
Dawn in the 2-mile-wide
caldera of Kilauea. Shallow
hot rocks produce steam
from rainwater percolating
through cracks.
GEOSC 10: Unit 3: Plate Tectonics II
Kilauea’s “Steaming Bluff”
occurs where faults parallel to
the 400-foot-high caldera wall
intersect the surface, allowing
steam to escape. (A caldera,
by the way, is a big, complex
crater.)
In the very-early-morning
picture from March 11, 2007,
above, the steam cooled and
then sank into the caldera
with a cool breeze. A little
later in the morning, left, the
steam was rising.
GEOSC 10: Unit 3: Plate Tectonics II
Ohi’a
flowers
GEOSC 10: Unit 3: Plate Tectonics II
Steam rises along faults parallel to but back from the edge of the
caldera, which is behind the camera. These faults were caused by the
tendency of rocks to slump into the caldera.
GEOSC 10: Unit 3: Plate Tectonics II
Karen Alley films her father in Kilauea’s Southwest Rift. The layered rocks behind Dr.
Alley (lava flows, plus pyroclastics--pieces thrown by the volcano) were split in 1971 to
form the rift when rising magma inflated the surface like a balloon; an eruption then
made the “lava fall” to Dr. Alley’s left.
GEOSC 10: Unit 3: Plate Tectonics II
Above, the Southwest Rift Zone of Kilauea as seen in March, 2007.
Right, an aerial photograph, taken in March, 1985, showing the rift.
The photo above was taken from the point marked by the tip of the
arrow in the right-hand picture, looking in the direction of the arrow.
The caldera of Kilauea is behind the camera in the picture above, and
at the very top of the picture to the right.
GEOSC 10: Unit 3: Plate Tectonics II
http://hvo.wr.usgs.gov/galle
ry/kilauea/caldera/4303019
_caption.html USGS photo
by J.D. Griggs.
Left, a fern struggles to grow just
below the toe of the 1971 lava
flow of Kilauea’s Southwest Rift
Zone. Above, the lush growth
near the mouth of Thurston Lava
Tube, on an older lava flow (about
400 years) on the eastern side of
the caldera, shows that the lava
will yield productive soils if given
enough time.
GEOSC 10: Unit 3: Plate Tectonics II
R
Complex geology. The large rock labeled R above Dr. Alley was thrown by an earlier eruption, and lies in a
layer of other pyroclastic pieces. Younger pyroclastic pieces slid off R, so those layers thin as they cross R.
The lava flow, the youngest layer, cascaded into the southwest rift to Dr. Alley’s right, ending just above the
yellow arrow.
GEOSC 10: Unit 3: Plate Tectonics II
Additional views of features in the
previous slide, from the Southwest
Rift of Kilauea, labeled in the
same way to make them easier to
recognize.
R
Later in the semester, you will get a chance to
read rocks and tell history--CSI Geology. Here,
for example, after some lava flows and big
explosions, the large rock R was tossed in, then
buried by additional things thrown by eruptions,
then the rift opened in which Dr. Alley stood to
take the pictures, and then a lava flow poured
across the top and down into the rift, now
ending near the yellow arrow.
If CSI Geology doesn’t make sense yet, don’t worry--it will later.
GEOSC 10: Unit 3: Plate Tectonics II
GEOSC 10: Unit 3: Plate Tectonics II
Volcanic gases include water and other chemicals, from rainwater circulating through rocks, but
also from deep in the Earth’s mantle. The atmosphere and oceans formed from volcanic gases. A
natural balance has existed for billions of years between the volcanic release of water, carbon
dioxide, sulfur (the yellow in the picture above) and other chemicals, and the return of those
materials to the deep Earth in subduction zones. Recently, human fossil-fuel burning has been
releasing carbon dioxide about 100 times faster than volcanoes do. This is another topic we’ll look
into later.
GEOSC 10: Unit 3: Plate Tectonics II
Halema’uma’u Crater, within the larger caldera of Kilauea, is now about one-half mile across and 300 feet deep. From 1905 to 1924,
a huge lava lake occupied the crater, often barely 100 feet below the rim (the prominent line marked by the yellow arrow shows
where the lava stood at one time). In 1924, the lake largely drained to feed an eruption of the East Rift Zone. Rocks fractured to let
the lava out, also letting water in, which flashed to steam and on May 18 caused a very vigorous eruption for “quiet” Hawaii, throwing
many-ton rocks as much as 1/2 mile (killing one person). The crater deepened to about 1500 feet, but by 1951 had filled to only half
that, and filled further in eruptions of 1974. You don’t need to memorize these details, but we thought you’d find them interesting.
GEOSC 10: Unit 3: Plate Tectonics II
Landslides have fallen down the steep crater walls, often
triggered by the shaking of the numerous earthquakes.
Notice that muddy water drained out of the big landslide
near the center of the photo, forming the light-colored
deposit at the point of the red arrow.
GEOSC 10: Unit 3: Plate Tectonics II
Thurston lava tube. About 400 years ago, lava drained through this 1030 foot high tube. A flow often hardens on the top and sides while
remaining molten inside, and the tube drains when the eruption ends.
Drips may harden on the ceiling as very strange “stalactites”. You’ll see
some active lava tubes in the next slide show.
GEOSC 10: Unit 3: Plate Tectonics II
Photograph by K. Shickman on 23 January 1990
http://volcanoes.usgs.gov/Products/Pglossary/tree
mold.html
Left: Looking down into a tree mold. When lava
hits a tree, water in the trunk boils, removing
heat and solidifying a “shell” around the tree.
The lava may then drain away, leaving the mold
sticking up. In this one, a new tree has rooted in
soil developed on the old flow, sending roots into
the space left when the old tree burned away.
The picture below, from the USGS, shows a tree
mold a few hours after formation, with the lava
still glowing and the tree fallen to the upper right.
GEOSC 10: Unit 3: Plate Tectonics II