708 E. S. MOORE 



been reports of sympathetic action in Ruapehu, White Island, and 

 other places along the volcanic zone. 



Previous to the eruption of Mount Tarawera there were numer- 

 ous hot springs and geysers in the area occupied by the present 

 Lake Rotomahana, and the famous Pink and White sinter terraces 

 were situated well within the border of the present lake. 



THE GREAT FISSURE 



As stated above, the eruption of Mount Tarawera began at the 

 northern end of the mountain and progressed southward with the 

 opening of an enormous fissure. This chasm is about 8f miles 

 long, if miles wide in Lake Rotomahana, and 900 feet deep in the 

 mountain. It is one of the most extraordinary openings to be 

 found anywhere in the earth's crust (Fig. 11). Where it cuts 

 through the mountain it takes the form of several deep, narrow 

 craters in linear succession, separated by wedges of rock not blown 

 out by the great explosions. The deepest opening is about 900 feet 

 and it is about 1,000 feet wide at this point. In some places the 

 crater walls are nearly vertical, but in others they have a gentle 

 slope and can be descended to the bottom. There are a few small 

 fumaroles, but they are no longer important. Along the brink 

 of the chasm there is about 175 feet of highly colored, red and 

 variegated scoriae deposited on top of the rhyolite materials thrown 

 out of the fissure, but there is no evidence of a lava flow. 



The fissure runs down the mountain side and through Lake 

 Rotomahana, where it is 520 feet deep and has very steep walls 

 in some places. It reached its maximum width here, where it is 

 ij to. if miles wide. The present lake is about 4 miles long and 

 2 miles wide, and it covers the areas formerly occupied by the old 

 Lake Rotomahana and Lake Rotomakariri. In the fissure, 

 immediately after the eruption, there was a small lake called Hot 

 Lake, but gradually the whole depression became filled with water. 

 The explosion completely destroyed the Pink and White sinter 

 terraces, which were located within the present basin rim, and 

 fragments of them may be picked up for miles around where they 

 are mingled with the other ejectementa from the fissure. There is 

 still much thermal activity around Rotomahana, the name of which 



