The following crater views are looking north toward Lake Natron from the summit of Lengai.

July 17, 1997. Note the large area of recent lava in the NW part of the crater. The photo was made by my
climbing partner, Scott Smith.

Approximately Aug 5, 1998.  Notice that lava had not yet crossed the NW crater rim.  The tall cone
in the center is T47.

July 25, 1999. The northernmost of the cones is T40, site of most activity from July 23-Aug 7. Since

1998, lava has spilled over the NW crater rim and also over the E crater rim. Those locations are now

referred to as crater rim overflows.

July 24, 2000.  Note the large aa lava flow in the south (lower) part of the crater.  In the upper right part

of the flow is a dark area of lapilli. This was probably all erupted on July 21 or 22, 2000.  The tall cone (T47)

near the center is essentially unchanged since 1998. The small dark cone to the upper left, just south of the

rim overflow, is a new cone called T51.  It was the site of activity on July 23 and July 28-30.

July 26, 2001. Spatter cone T51 at the left (west) side of the crater has grown much taller since 2000.

  Little change occurred in the SE two thirds of the crater during the previous year, in fact the aa flow

and lapilli field of approximately July 21, 2000 is still clearly visible in the south (lower) part of the crater.

  It is exactly as it appeared one year ago in the 2000 photo just above, except for its change of color

from black to pale brown. The tall pointed cone near the center is T47.  The new cone T53 is clearly

visible near the north crater rim, straight above (north of) T47.

July 28, 2001.  Lava originating from the T49 cone cluster (just north of T47)  flowed three ways across

the crater during the exceptionally large eruption of July 27-28.  The black lava flow of July 27 (lower left)

seems to have been the first lava to cover any part of the aa flow in the past year.  The eruption formed

a connecting ridge between cones T49D and T49B, making them more difficult to distinguish. Recent

rockfall from the crater rim is visible at right.

Aug 7, 2002. In the upper left (NW) part of the crater lava flowed from a new vent (T49F) on Aug 5th and

6th and destroyed our supply camp.  The black cones to the upper right were very new and two (T56 and T57B)

were erupting. To the far left is also a new feature, the W crater rim overflow. Spatter cone T58, formed by a

fissure eruption during 8-9 August, did not exist when this picture was made.

Aug 5, 2003. The prominent back cinder cone is T56B, and a smaller black cone, T58B, is situated

just in front and to the left of T56B's black slopes.  There are no fresh lava flows. Many old lava flows in

the southern part of the crater originated from a former lava lake at the base of T56B. The rim of the former

lava lake is visible as low ridge just in front of T56B. These flows have covered up a number of spatter

cones that existed in Aug 2002. There is no change in the width of the NW crater rim overflow since Aug 2002.

July 26, 2004. The tallest cone is T56B, and just in front of it the vent of T58B can be seen. To the lower
right of T56B is the new vent T58C.  It consists of 4 small cones and vents that cannot be distinguished

in this photo. The long narrow flow of  recent (black) lava toward the lower left was formed by eruptions

of T58B on July 23-24. Much of the white and black lava in the eastern (right) half of the crater flowed

during the violent birth of T58Con the late afternoon and evening of July 15, 2004.
 

Aug 7, 2005. The tallest cone is T49B. The cones from which the relatively young white lava flows

originatedare T58B and T58C.  Other than the growth of those two cones, there appeared to be relatively

few changes in the crater since late July 2004.

Aug 7, 2006.  Note the large collapse zone where T56B, T58B, and T58C once stood. The tall cone is

T49B. The dark lava on the right (eastern side of crater) is believed to have erupted around 20 June 2006

from T37B and lava lakes in collapse pit CP2 just beside it.  The dark lava to the lower left probably dates

from April 2006.  Although it appears dark and fresh, it has been highly altered by weathering and easily

crumbles into powder if touched.