THE ERUPTIONS OF MAY, 1902, AT THE SOUFRIERE IN ST. VINCENT. 
325 
I. 
II. 
Si0 2 
53-51 
48-71 
TiO, 
1-06 
1-08 
A1 2 0 3 
18-90 
18-40 
Fe 2 03 
3-37 
3-70 
FeO 
5-70 
5-33 
MgO 
4-38 
10-30 
CaO 
9-15 
10-11 
Na,0 
3 13 
2-34 
KoO 
0-51 
0-43 
P 2 0 5 
tr. 
0-06 
HoO 
0-12 
0-25 
99-79 
100-71 
I. Hypersthene basalt ( labrador it e a hypersthbne) from the Somma of the Soufriere (anal. P ISAM).* 
II. Olivine basalt from Chateaubelair Point (anal. Pisani).* 
All the rocks are basic types of andesite and basalts. Hypersthene and olivine are 
the characteristic minerals with highly zonal crystals of plagioclase. 
During the recent eruptions in Martinique and St. Vincent, in spite of all variations 
the more basic character of the ejecta in the southern island has been maintained 
throughout. Perhaps for this reason the outbursts have been fewer and less 
spasmodic; other consequences are the comparative scarcity of pumice, the absence 
of bread-crust bombs which were partly solid when they struck the ground, and the 
non-appearance of quartz in the new St. Vincent andesites. After the emergence of 
the dome in the crater of Pelee, many of the ejected blocks had a quartzose 
groundmass. 
The greater viscosity of the magma in Martinique led to the extrusion of the lava 
as a high pillar which rose from the crater. No counterpart of this is known on the 
Soufriere, where the floor of the crater is now almost exactly at the same level as 
before the 1902 eruptions. The more basic character of the rocks of the Soufriere 
probably accounts also for the greater abundance of anorthite-olivine blocks. 
In spite of these differences there is a great similarity between the products of the 
eruptions in Martinique and St. Vincent. Representatives of every type of rock 
described heref have been obtained by the French geologists from the active or 
extinct volcanoes of Martinique. 
The material of the eruption of 1902 is the most acid which has been found in 
St. Vincent, where also hypersthene andesites are most common in the Soufriere at 
the north end of the island. For a prolonged period this volcano has erupted only 
andesitic materials. In its earlier stages, when flows of lava were more common, 
* Lacroix, A., ‘La Montagne Pelee,’ p. 598. 
f With the exception of the albite rock described on p. 322 
