[Geysers] Upper Mortar initiated eruptions

[Tara Cross]

The fact that the 7/8/09 was initiated by Upper Mortar brought up the question of how long it's been since that type of start was last observed.  I made a quick check of the information I have on observed eruptions 2000-2009 and counted up the start types for each year.  Two important clarifications:

1. This list includes only OBSERVED eruptions that were reported to me in some way.

2. For an eruption to be Upper Mortar initiated, the eruption must start from a series of cone-filling surges in Upper Mortar, and the initiating surge must occur when Fan's minor vents are NOT having "lock" behavior.  Simply having Upper Mortar as the first major vent to start during "lock" behavior does not make it an Upper Mortar initiated start.


Key--UM = Upper Mortar initiated, LMM = Lower Mortar minor initiated

Type  Lock  UM  LMM  Total
2000    1      1     0       2
2001    1     17    3       21
2002   12    16     0      28
2003    7     11     0      18
2004    16    1      0      17
2005    9      0      0      9
2006    0      0      0      0
2007    5      0      0      5
2008   20     0      0      20
2009    1      1      0      2


The last known Upper Mortar initiated eruption prior to the most recent was on August 2, 2004, and that was the only one observed that year.

--Tara Cross
fanandmortar at hotmail.com

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