Historic Littoral Cones — M oore and Ault 
great number of basalt bombs and spatter. Many 
of the bombs are subspherical, with concentric 
structure, and show evidence of having flattened 
when they hit. Most of them are covered with 
fine cinders which adhered to them when they 
struck the surface of the growing cone. The 
bombs are commonly 3-5 inches in diameter, 
but some more than 1 ft in diameter are present. 
Large masses of spatter as much as 8 inches in 
diameter drape over the cinders as high as the 
summit of the cones. 
Puu Hou is notable in that it contains more 
bombs and spatter than the other cinder cones 
studied, indicating that a large amount of the 
material thrown into the air was still molten 
and was apparently not chilled and shattered. 
Very likely the steam explosions occurred near 
the base of a lava stream and threw molten 
material from the interior of the flow up onto 
the cone. 
1919 Cones 
The cone produced by the 1919 Mauna Loa 
flow is the smallest of the historic littoral cones. 
It is located on the southwest coast of the island, 
about 25 miles northwest of Ka Lae (Fig. 1). 
The cone is only about 50 ft above sea level and 
15-20 ft above the general level on the land- 
ward side. 
The 1919 Alika flow which formed the cone 
broke out 1 1 miles east of the coast at an eleva- 
tion of 7,500 ft on the southwest rift zone of 
Mauna Loa. The source vents opened about mid- 
night, September 28-29, and the lava reached 
the sea at 4:30 AM, September 30. This aa lava 
stream continued to flow into the sea for 10 
days. About 350 million cubic yards of lava 
were erupted, of which 200 million cubic yards 
flowed into the ocean (Stearns and Macdonald, 
1946:79). 
Many details of the contact of the lava with 
the sea were recorded by Thomas Jaggar of the 
Hawaiian Volcano Observatory (Jaggar, 1919: 
133-134). When the lava poured into the sea, 
he wrote: 
Noises were heard underwater of seething and of tap- 
ping concussions. The uprush of steam where the lava 
made contact with the sea carried up rock fragments 
and sand and built a black sand cone. The lava "rafts” 
or blocks of bench magma which rolled down the live 
channel, were seen to bob up, make surface steam, 
7 
and float out some distance from the shore without 
sinking at first, as though buoyed by the hot gas in- 
flating them. Lightnings were seen in the steam 
column. There was much muddying of the water and 
fish were killed in considerable number. . . . For 50 or 
more feet out to sea from the base of the great column 
of vapor which was rising opposite the lava channel 
somewhere beyond, the water was dotted with small 
jets and sometimes a swirling "steam spout” or tor- 
nado effect, a foot or two in diameter, would rise 
from the water a few feet away from the main steam 
column and join the cloud above. Sometimes a shower 
of small rock fragments each two or three inches in 
diameter would be jetted up from a place in the water 
close to shore, each projectile followed by a tail of 
vapor, to heights 15 or 20 feet above the sea. 
In describing the littoral cone as it appeared 
on October 23, a few weeks after the eruption, 
Jaggar stated (1919:151): 
This cone, at the lower terminus of the channel was 
built by the steam explosions resulting from the in- 
candescent torrent rushing into water, a crater being 
there formed, surrounded by a heap of black sand. 
This horse shoe heap was 7 5 feet high above sea level, 
and the front of it had broken down on the ocean 
side, revealing a section of bedded sands over a rock 
wall beneath. . . . The material was black and rather 
fine lava sand. . . . There were a few scattered small 
lava fragments on the surface of the sand. Everywhere 
the sand was coated with a thin film of crystalline 
white salt, common sea salt, to judge by the taste, and 
this made the cone white as seen at a distance. 
The 1919 cone is composed of crudely bedded 
glassy ash and cinders. In the sea cliff this pyro- 
clastic material is about 40 ft thick and extends 
from the crest of the cone almost to sea level, 
where it rests on top of a shattered and con- 
torted lava flow. It is not known whether this 
flow is a 1919 lava flow or is older. 
The east (landward side) of the cone is 
partly covered by a younger lobe of the 1919 
flow. This lobe flowed on top and around the 
north side of the completed cone and reached 
the sea, forming a prominent peninsula con- 
taining a major channelway. In the sea cliff this 
younger lobe lies on top of the littoral cone ash 
and cinders and has baked them to a reddish 
color for a distance of 4 ft below its base. The 
younger lobe is not covered by cinders and 
apparently marks the last phase of the 1919 
lava which flowed into the sea after the cone 
was formed. 
The lower part of the clastic material of the 
