VOLCANIC CRATERS AND EXPLOSIONS—DISCUSSION. 
129 
there is singularly little evidence of explosive action, such as the presence 
of ash, lapilli, or ejected bombs, all of which are very infrequent even right 
up to the brink of the crater. The details of its structure were shown by 
the aid of a series of photographs taken during a month’s stay at the 
volcano house. These showed among other things the lake of liquid lava, 
partly crusted over, and with the crust broken up by a series of cracks, 
through which the red-hot molten lava was visible at dusk, and which were 
photographed by their own light, as was Old Faithful, the great fountain 
of molten lava, which usually plays at intervals about once a minute or 
oftener. Bays were also formed in the crater during this visit by the 
remelting of parts of the black ledge f of lava. They were comparable in 
size to the quadrangle of Burlington House, and the lava which was 
remelted was entirely removed. 
Matavanu is a new volcano in Savaii, an island in the Samoan group, 
which only came into existence in 1905 . Its crater | contains a lake, or 
rather river, of molten lava, comparable to, but more active than, that of 
Kilauea. The incandescent lava is so hot as to appear white-hot, even in 
tropical sunlight, so fluid as to rise in fountains more active than those in 
Kilauea, and to break in waves on the walls of the crater. Finally, the 
lava rushes with the velocity of a cataract into a tunnel, or rather gulf, at 
one end of the crater, where it disappears and runs underground under the 
crust of a large lava-field f for a distance of 10 miles to the sea, into which 
it falls with tremendous explosions.“j* Its course under the lava-field is 
marked by a number of large pits or fumaroles,f which appear to have 
been formed by the remelting and falling in of the crust over the tunnel. 
They are very similar in structure f to the pit craters of Hawaii, f the origin 
of which has given rise to so much discussion, and which were possibly 
formed in a similar manner. 
As the lava at the seaside escapes from under the surface crust, it, where 
the action is not sufficient to set up explosions, begins to form lobes like 
those of ordinary corded lava j—and this corded structure is, in fact, formed 
in the usual manner in places above the water-level. Where, however, 
it falls direct into the sea, the surface is chilled before there is time for it 
to be wrinkled up into the corded structure, and it becomes consolidated 
into the characteristic form of one variety of pillow-lava.f This mode of 
formation, though previously on other grounds suspected by geologists, 
was, it is believed, first actually watched by the author in 1909 . 
The President (before the paper): The reader of the paper to-night, Dr. 
Tempest Anderson, bears a name well-known to geographers. Many of you 
here present are familiar with the work he has accomplished in connection with 
some of the greatest volcanoes in the world, and with the magnificent photo¬ 
graphs with which, when he lectures to us, he illustrates their activity, and the 
effect exercised by them upon the surface of the globe, which is, of course, the 
main study for which geography exists. Eight years ago Dr. Tempest Anderson 
f Slide shown. 
