HAWAIIAN LAVA FLOWS
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Scott K. Rowland, University of Hawai‘i at Manoa
Lava flows: ‘a‘a- and pahoehoe
From Hawaiian Dictionary by M.K. Puku‘i & S.H. Elbert
- 1. To burn, blaze, glow; fire; staring, as eyes. Fig., angry,
‘a‘a:
fury. Ua ‘a‘a-‘ia au i ke aloha (I burn with love). 2. stony,
abounding with ‘a‘a- lava.
pahoehoe:
1. Smooth, unbroken type of lava. 2. Satin.
3. to drive fish into a net by beating the paddles
rhythmically against the canoe.
Lava flows: ‘a‘a- and pahoehoe
These two types of flow are identical chemically, their
differences are due to different emplacement processes
(flow rates, cooling rates, etc.).
- - - to gush, ooze forth
Pahuhu:
Ho‘opohaku:
to harden, as lava
(Courtesy of Ululani Makue)
‘a‘a-high volumetric flow rate
(10-103 m3 s-1)
-high flow-front velocity
(102-104 m hr-1)
-develops large channels
-few, large flow units
-thick (1-10 m) flow units
-higher viscosity
-higher yield strength
-slightly cooler
-“apaluhraun” (rough lava)
in Icelandic
pahoehoe
-low volumetric flow rate
(<10 m3 s-1)
-low flow-front velocity
(1-10 m hr-1)
-develops lava tubes
-innumerable flow units
-thin (10-100 cm) flow units
-lower viscosity
-lower yield strength
-slightly hotter
-“helluhraun” (pavement lava)
in Icelandic
These terms are “…the barbarous expressions of an insignificant and
uncivilized race in a small archipelago in the Noth Pacific…” (Bonney, 1899)
Stone for making implements:
- lots of vesicles, easy to shape by “pecking”,
Pohaku
‘eleku,
(usually the interior of a pahoehoe
flow)
- few or no vesicles, breaks along planar fractures,
Pohaku
‘ala,
difficult to shape but good for cutting tools
(the core of an ‘a‘a-flow or dike rock)
Note that the personal preferences of the stone worker entered into the decision as well,
as shown by portions of an interview of Herbert Kuumi Kin In (HKI) by William Meinecke
(WM) and Mary Kawena Pukui that contains the following:
WM: Ah no, the ‘āla was too smooth. Stones with little holes, that’s this.
HKI: Yes, coarse, vesicular basalt. That is the pōhaku ‘elekū
WM: ‘Elekū, that’s right.
HKI: Good stone for hewing. Pōhaku ‘alā, hard, one has to handle carefully they break.
WM: There’s one fault, that makes people dislike the ‘alā, because it’s not porous at the base,
and the stone slips when pounding poi.
HKI: Ah, I prefer the ‘alā.
(Bishop Museum Archives Manuscript/Typescript no. HAW ID5.7.1,
typescript pp. 18-19)
‘a‘a- and pahoehoe
flows on the north flank of Mauna Loa
~3 m
Wave-cut cliff section, Makapu‘u, O‘ahu
‘a‘a- flows
Proximal-type ‘a‘a- flows
-relatively thin
-vesicular interior
-thin top and bottom
clinker layers
When moving, the incandescent interior is deforms fluidly
~1 m
The top surface is relatively small, spiny clinkers
Distal-type ‘a‘a-flows
standard geologists
for scale
Distal-type ‘a‘a- flows:
-dense, angular, large surface
blocks
-incandescent lava has a high
yield strength
-advance is by avalanching of
loose blocks and fine material
George Walker, walking around on the surface of the (active)
1984 Mauna Loa distal-type ‘a‘a -lava flow
Three relatively thin ‘a‘a- flows in cross section
clinker
flow cores
Accretionary lava balls
~1.5 m diameter
pahoehoe
flows
Flow field of pahoehoe
“toes”
(individual flow units)
~0.5 m
Old pahoehoe
flows in cliff section, Kaua‘i
~2 m
pahoehoe
issuing from a crack in a previous toe
~40 cm
active pahoehoe
toe
~20 cm
Stretched vesicle walls on the skin of s-type pahoehoe
~10 cm
The interior of an s-type (“spongy”) pahoehoe
flow
Folding of the plastic surface crust: ropy pahoehoe
Side view into an active lava tube
Master lava tubes can be
many meters high and wide.
Note that during a tube-fed
eruption, the main tube is
almost as long as the flow,
but that afterwards it
almost never drains completely.
Lava trees (~2 m high)
A forest of lava trees, partially buried by scoria
‘Olelo
no‘eau involving lava (from M. K. Pukui; compiled by Ululani Makue
O ka la- ko luna, o ka pahoehoe
ko lalo. The sun above, the
smooth lava below. Said of a journey in which the traveler
suffers the heat of the sun above and the reflected heat
from the lava below (a difficult trip).
- - ke ‘ala,
- uwe
- ka mamane.
Kike
When the boulders clash, the
mamane
tree weeps. Meaning that when two people fight,
those that are dear to them often weep.
PAU
Solidified dikes are exposed by erosion on old Hawaiian volcanoes
If a whole lot of dikes are exposed, it means that erosion has exposed
the core of an old rift zone
Here are a whole bunch of dikes in a roadcut near Windward Community
College (unfortunately they’re now covered by a wall). Photo by F. McCoy
The axis of one of the Wai‘anae
Volcano rift zones is exposed in
the cliff at Kaneana.
Makua
cave
Farrington Hwy.
Dike rock is usually more resistant to erosion than the lava flows that
the dikes are cutting through. They end up standing above the moreeroded flows to form narrow blade-like ridges.