Photo Essay for Pierce College's Hawaii Island Field Excursion 2011.

1. Brian Shoaf
2011

2. (courtesy of Google Earth)
The Emperor Seamount and Hawaiian Island Chain are a geologically peculiar archipelago in
the middle of the Pacific Ocean that lies thousands of miles away from any tectonic plate
boundary or continent. This chain of volcanic islands are among the most geographically
isolated places on earth.

3. The current paradigm suggest the
formation of the Chain was caused by
the “hot spot” it sits atop. A hot spot is
an area deep within the earth‟s interior
that erupts Molten rock from beneath
the ocean floor. Over time, volcanic
gasses and basaltic lavas from the
eruptions build to sea level and
continues the process upwards,
gradually forming a volcanic island.
eventually the Pacific plate functions as
a conveyor belt and carries each island-
volcano northwest from the hot spot at
an estimated 4 inches per year. The
island of Hawai‟i, or “The Big Island”
is still under-going this process, being
the only island on the archipelago that A diagram of the Hotspot (USGS)
currently sits on the hot spot, aside from
the submarine Lo‟ihi seamount.

4. Unlike the volcanoes we‟re accustomed to seeing here at home, the
volcanoes of Hawaii are gently sloped with wide summits –
think „naturally-occurring Tacoma Dome‟ . Because of the
high-temperature magma of the hot spot, the chemical
composition of these eruptions are fluid often allowing lava
flows to go on for years at a time. This long, gradual process of
erupting builds the gentle slopes of lava around the magma
vents.
Classification of shields are determined by the distance of the
flows around the vents, if the flows are only a few miles across
they‟re considered lava shields, examples of these from the trip
are Mauna Iki and Mauna Ulu. If the mounds span more than a
dozen-or-so miles, they‟re called Shield Volcanoes.
Mauna Loa and Kilauea are the youngest and most active volcanoes on
the archipelago. These are two classic examples of shield
volcanoes. Mauna Loa, with an estimated volume of up to
19,000 cubic miles beginning at its depressed seafloor base is
the largest volcano on earth in terms of mass. The slopes of
these volcanoes are littered with volcanic features such as lava
shields and cinder cones that formed during single eruptions
from the magma chamber. Like most geologic features, shield
volcanoes go through long stages of formation and de-
formation. The three phases are the first alkalic stage, where
small volumes of basaltic lavas form, the second is the Shield Mauna Loa’s gentle slopes
Building stage, where large volumes of thoeleiitic basalt build,
and finally the Second Alkalic stage where the basalt is once
again alkalic with low volume. Because the location of The Big
Island relative to the Hot Spot, these young volcanoes are still
amidst the early building stages. Mauna Kea, Hawaii‟s tallest
mountain (above sea level) is in the Late Second Alkalic stage.

5. Shield Volcanoes are essentially
huge unstable piles of basalt that
spread over time under their own
mass. During the spreading process,
fracturing occurs on the flanks of
the volcanoes and often allows
magma to encroach into the flanks,
often causing eruptions far from the
summit of the volcanoes. These
areas of the volcano are called rift
zones. Shield volcanoes like Mauna
An aerial view of Mauna Loa’s northeast rift. (J.P. Lockwood, USGS)
Loa usually have three rift zones,
but younger volcanoes like Kilauea
– that builds on the eat rift of
Mauna Loa has only two rift zones.

6. Cinder Cones usually form during the
second alkalic stage of shield
volcanism. They form when there
are axial cracks on the surface of
tumuli that allow magma to escape
from their vents. They have the
physical appearance of classic
volcano imagery we all saw
growing up, but on a smaller scale.
These structurally-weak volcanic Three cinder cones at Mauna Kea’s summit
features usually erupt only once in
their lives, when the last of the
volcanic gases escapes their craters.

7. When lava first erupts from a magma vent
it is usually very fluid with low
viscosity. As it travels down slope,
the physical properties may change
based on the speed of the flow and/or
the terrain it travels across. As it
travels downward, the lava‟s
temperature cools and subsequently
gains density.
Although the flow comes from the
same source, physical properties like
gas content of the magma,
temperature and rate of travel
ultimately determine what type of
lava it becomes.
We saw two different types of flows,
pahoehoe and a‟a, which I have
described above (respectively).
A field drawing of two lava flows
off Saddle Road

8. Pahoehoe lava has a smooth physical
appearance, runs fluidly and can be classified
into three different types: entrail, ropy and
shelly. These three types of pahoehoe are
classified by their texture.
Entrail pahoehoe forms when pahoehoe toes travel
at a relatively quick rate down slope. To
entrail
identify entrail pahoehoe, look for a flow with
a thick, furrowed appearance.
As the pahoehoe flow moves down slope, it
gains viscosity and may form a plastic-like
coat that allows lava to continue flowing
beneath it. When this happens, the Pahoehoe ropy
may form a coil-like structure due to the
traveling lava, we call this type ropy
pahoehoe.
As the pahoehoe solidifies, it may also
display a cracked, turtle shell-like texture, this
type is known as shelly pahoehoe
shelly

9. Unlike pahoehoe, a‟a is a type of
basaltic flow that has a rough, jagged
surface with a dense interior full of gas
bubbles. It forms when thick, cooler
lava breaks apart as it travels down
slope.
This picture of Amanda meditating on Pahoehoe is a
great shot to differentiate the two different types of
flows. Pahoehoe being the lighter gray basalt, and a’a the
darker reddish basalt.

10. Lava tubes come in all shapes and sizes. On the trip
we explored the depths of two massive lava
tube caves and also observed several that
ranged from a few inches to several feet in
diameter.
Lava tubes start as any other flow channel, as
the lava cools the outside margins begin to
solidify, the hardening process eventually
forms a roof structure and unlike most flows
that harden completely, these flows leave a
core of flowing lava that is surrounded by the
margins. Once the flow has run its course, the
lava channel empties leaving a hollow tube,
similar to if you were drinking out of a straw
that had walls formed by a margin of your
hardened beverage.
Inside of a bigger lava tube

11. When lava travels through wooded
areas or forests, most of the trees
become engulfed by fire, but
sometimes, moisture-rich woods in
some trees may cool the lava that
surrounds it. As the flow gradually
recedes, the hardened lava that
surrounds the tree remains, leaving a Lava tree
cast around the tree. The layer of lava
that encompasses the tree inhibits
further growth and eventually kills it,
but the hardened pillar remains, making
it a lava tree.
In a case where the lava flow continues
without receding the area, trees may
become overpowered by the flow. Over
time, the trunk may decay and leave a
vertical, well-like tube that we call a Tree mold
tree mold.

12. A caldera is a sunken depression at
the top of volcanoes. Calderas can
occur as either of the following:
Explosive calderas are the outcome
of an outward explosive eruption
from avolcano, Crater Lake in
Oregon is an example of this.
Collapsed calderas are pit craters
on a larger scale. As lava lakes are
drained from underground and
eruptions occur, sunken or
collapsed summits may result due
to the weight of the edifice.
Kilauea Caldera, a 2.5 by 2-mile
caldera that is currently
experiencing activity within its
Halemaumau crater within Kilauea Caldera
limits at the Halemaumaucrater,
was a collapsed crater that we saw
on the trip.

13. There are two different types of craters,
explosion craters and pit craters.
Pit craters are formed by tensional stress
caused by the recession of magma,
resulting in the upper-most crust
sinking and collapsing into the
receded area beneath, creating a
scarp.
In contrast, explosion craters form
when a subterranean explosion
occurs and erupts debris or tephra
from the source. Mauna Ulu Crater

14. Faults are abrupt fractures in a volume of rock that
has undergone significant displacement.
When energy is released from fault systems,
seismic activity usually occurs.
During the trip, we studied the Koa‟e fault
zone with renowned geologist Don Swanson
of Hawaii Volcanoes Observatory. The Koa‟e
fault zone is an area that connects Kilauea‟s
southwest and east rift zones. Seismic activity
at Koa‟e is caused by the massive weight of
Kilauea Volcano and has been home to
earthquakes that have left cracks up to 80
meters deep in some places. This area is
known as one of the world‟s most active fault
zones.

15. A scarp, or “pali” in Hawaiian, is an
expression of faulting as a result of
activity or fault movement that
causes structural displacement.
Scarps contain fractured rocks and
can be very steep.
HoleiPali slump scarp is a type of fault
landslide that drops debris into the ocean
and can cause a tremendous threat that I
will talk more about in the Hazards
section of the project.

16. Within this fault zone lies an area
known as White Rabbit, named after a
1960s song by the psychedelic band
Jefferson Airplane. This fault is one of
Koa‟e‟s numerous thrust fault scarps.
White Rabbit is a 2.5 km-long fault that
faces uphill towards Kilauea‟s summit
and is a continuation of the east rift. The
last major faulting event was an
earthquake that took place on Christmas
Eve 1965 that caused an 8 foot vertical
offset of a 500-700 year-old flow.

17. Ring faults are circular fractures that develop
around emptied magma chambers.
Kilauea Caldera is surrounded by a
circumferential ring fault that also
functions as a binding for Kilauea‟s
southwest and east rifts
Part of Kilauea caldera’s circumferential ring fault system

18. Steam vents are series of roughly
parallel vents that are caused by shallow
sources of magma (1 kilometer or less)
that steams groundwater from below the
ground‟s surface.
Sulfur banks are the result of deep faults
extending down to the magma layer
where volcanic gasses seep from the Sulfur vent
ground when mixed with the
groundwater steam. The sulfuric gasses
are rich with hydrogen sulfide, carbon
dioxide and sulfur dioxide. Green
crystal deposits and a brownish to red
clay substance are known to form
around the surface of the vents due to
the released gasses from the steam.
Steam vent

19. Being a resident of Hawaii may be
a dream to some people, but it
doesn‟t come without its fair share
of risks.
Because Hawaii is essentially a
huge chain of either inactive or
active volcanoes, obvious volcanic
risks like explosive eruptions, lava
flows, towering lava fountains and
the release of dangerous volcanic
gasses may occur.
Other other dangers such as
earthquakes and tsunamis are also A former part of Chain of Craters Road where
more likely to occur in Hawaii than a Pahoehoe flow took over
other places in the world, creating a
hazardous environment for all of its
inhabitants, not just humans.

20. Volcanic eruptions may come in several
forms. A lava fountain, like the one that
occurred at Kilauea Iki, is a visually
astounding eruption that spews lava
thousands of feet into the air.
I‟ve discussed lava flows, a slow-moving eruption
that occurs often in on the island of Hawaii.
The two types of eruptions I‟ve listed above
can be easily monitored and their vicinities
can be evacuated to avoid potential hazards to
life.
Explosive Eruptions
To be considered an explosive eruption, there
needs to be a form of tephra, airborne lava
fragment, erupted into the air.
Explosive eruptions in Hawaii are believed to An explosive eruption at Kilauea
occur due to groundwater coming into contact
with magma and creating steam. This
tremendous force of steam can cause an
eruption if a present lava lake recedes below
the water table and collapses, allowing the
built-up pressure of the steam to escape in the
form of an eruption.

21. Pele’s
Hair Ash In-order from smallest to
Lapilli largest, tephra comes in all
shapes and sizes. Pele‟s hair
Cinders is different among most other
units because of its hair-like
appearance.
Blocks
Bombs

22. Organizations like the U.S. Geological
Survey‟s Hawaiian Volcano
Observatory monitors volcanoes
and earthquakes to observe patterns
of past, current and future eruptions
and study the process of the
activity.
Monitoring of ground and volcanic
activity includes real-time video (HVO courtesy of USGS)
capture, seismometer testing,
tiltmeter recordings, GPS mapping
and sample-taking.

23. The most common rock type
found in Hawaii is the igneous
basalt. Basalts are usually dark,
fine-grained in texture, and are
extrusive. Basalt is a rock that
forms when lava cools and
solidifies and is common
throughout the world, but seen
everywhere in Hawaii because
of the islands‟ volcanic make-
up.
TheBlack Sand Beach (Punaluu
Harbor) was produced by the
rapid cool down of a volcanic
explosion, causing the fine
black sand debris.

24. The most common mineral
observed on the trip was olivine.
This magnesium iron silicate
crystallized from magnesium-rich
magmas that are low in silica. The
olivine we saw in Hawaii were
always features on basalt, a mafic
rock, but can also occur in
ultramafic rocks like peridotite.
The Green Sand Beach of The Big
Island gets its name from the
greenish color of the sand there that
is caused by eroded olivine from
basalt. Under the magnifying glass,
I saw that the sand appeared to
have an 80 – 90% olivine content, a
much higher level than in previous
years.

25. Pumice
Is a lightweight highly-pressurized
volcanic rock that is created by
rapid magma eruptions.
Reticulate
Reticulate gets its name from the
hexagonal shape of its holes. It is a
type of pumice that is found only at
volcanoes that erupt basalt. It has a
soft spongy texture with a 98%
Part of a CE ~1500 reticulate layer at Kilauea
bubble content

26. Rain shadow Elevation Zones
Most of Hawaii‟s rainfall comes Hawaii has six distinct
from windward trade winds while elevation/vegetation zones that
the leeward flanks stay relatively include (from sea level):
dry. This makes for an enormously 1. lowlands
diverse climate for an island of its 2. mid-elevation woodlands
size.
3. rainforest
4. upland forests and
woodlands
5. subalpine
6. alpine/aeolian
(Courtesy of NOAA Climate Services)

27. Succession
Succession is an ecological process by
which a community sees changes over
time, then progressively forms into a
stable community. Succession is often
triggered by geologic catastrophes like
eruptions, earthquakes or tsunamis.
Primary succession is when a former
landscape is destroyed and there are
little to no living organisms left behind.
In Hawaii, Primary succession is
common because of its highly active
volcanoes. Secondary succession is
when an environment is disturbed, but
not obliterated like an environment that
Kipukas are islands of older lava that have been
would undergo primary succession. In surrounded by more recent flows. Primary succession
secondary succession, living organisms surrounds this particular kipuka.
can remain, but in smaller numbers. A
forest fire is a leading example of a
cause for secondary succession

28. Hawaii‟s rich cultural history began
when Polynesian rigger canoes first
arrived on the islands around CE 500.
These settlers brought with them most
of Hawaii‟s trademark tropical plants,
animals and a rich tradition of
agroforestry and farming.
Hawaiians are known to have always revered
their natural surroundings, especially
the islands‟ volcanic features. Pele, the
A painting of Pele at Jaggar Museum
Hawaiian goddess of volcanoes is said
to live within Kilauea caldera, where
she often shows her magnificence
through displays of eruptive power.
Reverence was also displayed through rock
carvings, known as petroglyphs, near
the shore where new mothers were
believed to have gave their newborns
umbilical cords as an offering of unity
with nature and their family.
Hawaiian petroglyphs

29. Google Earth. Web. 10 Oct. 2011. <http://earth.google.com/>.
Hazlett, Richard W., and Donald W. Hyndman. Roadside Geology of Hawaiʻi
.
Missoula, MT: Mountain Pub., 1996. Print.
Stone, Charles P., Linda W. Pratt, and Danielle B. Stone. Hawaii's Plants and
Animals: Biological Sketches of Hawaii Volcanoes National Park.
Honolulu, HI: Hawaii Natural History Association, 1994. Print.
USGS Hawaiian Volcano Observatory (HVO). Web. Oct. 2011.
<http://hvo.wr.usgs.gov/>.