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1998 Expedition

Page history last edited by Frederick Belton 13 years, 3 months ago

During 1998 there were some problems with attacks by Somali bandits in the Rift Valley around Ol Doinyo Lengai, but I was lucky enough to visit the region twice without incident. I spent July 17-21 and August 2-6 camped inside the north crater of Ol Doinyo Lengai with my Tanzanian guide, Paul Mongi. There was a great deal of activity at two spatter cones on the crater floor, which have been designated on crater maps as T48 and T37N1.

Approaching Ol Doinyo Lengai from Engaruka.

A climb to the active north crater of Ol Doinyo Lengai reveals a beautiful and dramatic landscape, especially in early morning light.

Spatter cone T48 is erupting splashes of natrocarbonatite lava, with cone T44 in the background.

Ropy (pahoehoe) lava flows from T48. The dark black lava is liquid and flowing and contains very little gas. The lighter black is recently cooled and probably still hot. The white lava at the top and bottom of the picture has been weathered by moisture absorption. The whitening can happen slowly over a period of several days or within seconds if it is raining.

Small lava channels such as this one often form during sustained eruptions. This channel near T48 is about 2 inches (5 cm) wide.

Typical weathering of a lava flow. Often the white color is first seen around the edge of a flow. Thin flows usually turn white much faster than thicker flows. This lava appears to be one or two days old, although the rate of weathering can vary a great deal depending on the level of humidity. Rainfall turns new lava white immediately, even when it is still hot.

Here is another example of the rapid weathering of Lengai's natrocarbonatite lava. A fresh black flow often becomes white around the edges after less than 24 hours. Thin flows turn white faster than thicker flows that retain their heat longer.

This is gas-rich lava from an eruption of T48. A pressure increase at the source of the flow is causing the lava to overflow the sides of the open channel. After the eruption ended a few hours later, I was able to climb inside this channel and enter a short distance into a large lava cave that did not exist the day before. High temperatures inside the cave limited my stay to a few seconds.

Fred Belton stands near gas-rich lava emerging from hornitos that have formed over the lava tubes from T48.

This horizontal lava fountain resulted from a rupture in the side of a lava tube that formed on the south flank of T48. The low point on the NW crater rim is in the background.

Fred Belton standing just south of the base of T48. The lava fountain is being fed by the tube from the summit of T48.

From July 18-21 this lava pond inside the large cone T37N1 frequently overflowed and formed long lava flows on the crater floor.

Looking west from T37N1 at a new lava flow from the pond shown in the previous photo. The tall cone to the left is T47.

This long slender lava channel was formed on July 20 by an eruption of T37N1.

A bursting lava bubble in T37N1 splashes against the underside of a newly formed overhang. This flash photo was taken at very close range on the night of Aug 6, 1998. The flash made it impossible to see the orange glow of the lava.

Early morning light of Aug 6 gives a striking appearance to this cone on the side of T37N1 which erupted numerous times during the previous night. Lava was visible inside the cone when this picture was made.

These stalactites and "soda straws" were in a cave near T40. They were not formed from dripping lava but are a result of chemical reactions within the lava after it has solidified, and are essentially the same composition as the white deposits that often form around cracks on cooling carbonatite lava flows. Roger Mitchell of Lakehead University has found that they are mainly composed of natron (hydrated sodium carbonate Na2CO3.10H2O) and aphthitalite (K,Na)3Na(SO4)2.