Ol Doinyo Lengai volcano (Tanzania), activity update: shallow magma present
During our latest expedition to the active crater of Lengai volcano from early 31 Jan - 2 February 2007, no eruption of natrocarbonatite lava occured from the summit vents. According to local Maassai guides, the central area of the crater with the large collapse pit near the tall hornito T49b had not seen significant changes since last summer.
From an open vent in the NE corner at the bottom of the pit at the base of the hornito, loud washing-machine like sounds of boiling lava was audible all the time. A large pool of lava must be found somewhere at very shallow depths in some caverns beneath that area. This assumption is confirmed by the glow of lava that was clearly visible one night from a second, smaller vent located about 30 m south of the large vent in the base of the collapse pit. One guide confirmed he had seen spattering of lava from this vent some two weeks earlier.
In addition to the loud sound of revolving lava underground, a constant, deep rumbling could be heard from the ground, resembling the sounds of very distant thundering. It was strongest in the NW area of the crater between the collapse pit and the fissure vents of the March 2006 lava flow. We think it might be an audible form of volcanic tremor more or less directly related to a magma volume still inside the same dike. When talking to local guides, they believe that a new, large-volume effusive eruption of lava from a similar area as in March 2006 might occur in the near future.
A GPS survey and some photographs of the area will be published here in the near future.