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Glossary and Abbreviations

Geyser Terminology

The following words are commonly used to describe eruptive activity. Geyser terminology is not always applied consistently to different geysers, but the following definitions will provide you with a starting point.

geyserA feature that periodically erupts a mixture of water and vapor.
perpetual spouterA feature that continuously erupts a mixture of water and vapor.
bubble showerVigorous boiling at the surface of a pool (e.g. activity at Beach Spring and Crested Pool).
preplaySplashes that occur prior to an eruption.
eruption startThe beginning of the water phase, usually the first burst of water. Note: Its defintion is geyser-specific (e.g. "one-meter boil" for Great Fountain).
water phaseThe part of an eruption dominated by water.
steam phaseThe part of an eruption dominated by vapor.
eruption endThe end of the water phase and for eruptions with a steam phase, the transition to steam phase.
durationThe time between the start of the eruption and the end of water phase.
intervalThe time between two eruption starts.
quiet intervalThe time between an eruption end and the start of the following eruption.
seriesA group of eruptions with similar intervals separated by a relatively long interval (e.g. Lion and Dome). The first eruption in a series is usually called the initial.
burstA segment of a single eruption that is separated by a brief pause (e.g. Grand). Note: Bursts are called series at Great Fountain.
post-eruptiveThe state of a geyser after it has finished an eruption. Experienced observers may be able to assess post-eruptive behavior to determine an approximated start time of a missed eruption.
major and minorEruption types. Major eruptions are usually defined by their greater intensity, taller height, and/or longer duration (e.g. Castle and Lone Star). Note: The designation of major eruptions at a certain geyser does not necessarily imply that the other eruptions are designated minor, and vice versa.
long and shortMajor and minor eruptions of Old Faithful. Short eruptions last for ≤2.5 minutes and long eruptions last for >2.5 minutes. This distinction is important because Old Faithful has a bimodal interval distribution, and the eruption type controls whether the next interval will be shorter (average 68m) or longer (average 94m).

Time Code

ieIn eruption. Eruption was observed, but not from start.
nsNear start. Eruption was observed within a minute of the start.
EElectronic. Eruption was determined using monitoring data (e.g. runoff temperature).
AApproximate. Eruption was observed, but exact time not noted and therefore later approximated, or eruption not observed and inferred from post-eruptive activity.
wcWebcam. Eruption was observed via webcam.
iniInitial. Eruption was the first eruption in a series of a geyser known to erupt in series.
(?)Questionable. Observer thinks that an eruption occurred, but isn't sure.
majMajor. Eruption was a major eruption of a geyser with different eruption types.
minMinor. Eruption was a minor eruption of a geyser with different eruption types.

Duration Code

~Approximately. Eruption is known to have lasted about the given time.
>Greater than. Eruption is known to have lasted at least the given time.
<Less than. Eruption is known to have lasted no more than the given time.

Grand Code

D#Turban Delay. The interval between Turban eruptions was 25m or greater. The number after the letter "D" is the number of Turban eruptions until Grand started after the delay.
V#Vent Delay. Vent overflowed but Grand didn't start even though it was time for Turban or Turban started. The number after the letter "V" is the number of Turban eruptions until Grand started after the delay.
GGrand. Eruption was initiated by Grand.
TTurban. Eruption was initiated by Turban which started shortly before Grand.
*Star. Duration of the second burst was 1m15s or greater.
#Pound. Duration of the third burst was 1m15s or greater.
CContinue. Vent & Turban continued after the eruption.
QQuit. Vent & Turban quit after the eruption.

The following examples may help to clarify the meaning of the codes:

  • T2*C: Turban started before Grand, two bursts, second burst was >1m15s, Vent and Turban continued
  • V2/G1Q: Grand erupted two Turban cycles after a Vent delay, Grand started before Turban, one burst, Vent and Turban quit
  • D5/D2/T1C: Turban delay, then another Turban delay five cycles later, then Grand erupted after an additional two Turban cycles, Turban started first, one burst, Vent and Turban continued

Great Fountain Code

p=#Pause. The quiet pause between the "one-meter boil", the start of the eruption, and the first burst of water. The number after the equal sign is the interval of the pause in minutes.

Geyser Group Abbreviations for Yellowstone

AbbreviationGeyser Group
BBGBiscuit Basin
BSBBlack Sand Basin
CDGCascade Group
CGGCastle, Grand and Sawmill Groups
CLCChain Lakes Complex
CLXCulex Basin
DSGDaisy Group
FCGFairy Creek Groups
FLGBlack Warrior (Firehole Lake) Group
FTNFountain Group
GFGGreat Fountain Group
GHGGeyser Hill Group
GIBGibbon Geyser Basin
GNTGiant Group
GRGGrotto Group
HFGHeart Lake's Fissure Group
HLGHeart Lake's Lower Group
HMGHeart Lake's Middle Group
HRGHeart Lake's Rustic Group
HUGHeart Lake's Upper Group
IMPImperial Group
KLDKaleidoscope Group
LSGLakeshore Group
LSTLone Star Group
MGBMidway Geyser Basin
MGGMorning Glory Group
MHGMarshall's Hotel Group
MMGMorning Mist Group
MMSMorning Mist Springs
MYRMyriad Group
NBKNorris Back Basin
NPRNorris Porcelain Basin
OFGOld Faithful Group
ORGOld Road Group
OSGOrange Spring Group
PBGPunch Bowl Group
PINPine Springs
PMGPipeline Meadows Group
PNKPink Cone Group
POTPotts Hot Spring Basin
QAGQuagmire Group
RSGRound Spring Group
RVGRiver Group
SDPSerendipity Springs
SHOShoshone Geyser Basin
SMGSentinel Meadows Group
SPRSprinkler Group
TGGTangled Geysers
THDThud Group
UPGUpper Springs
WCGWhite Creek Group
WDGWhite Dome Group
WSGWestside Group
WTLWest Thumb Lower Group

Other Abbreviations

UNNGUnnamed Geyser
TDTemporary Designation
UGBUpper Geyser Basin
LGBLower Geyser Basin
NGBNorris Geyser Basin
GOSAGeyser Observation and Study Association
OFVECOld Faithful Visitor Education Center
OFVCL-EVOld Faithful Visitor Center Log - Electronic Version
RTEDRalph Taylor Electronic Data
VRVisitor report. Used in the comments or observer fields when the entrant received word about the geyser activity from a Yellowstone visitor.
FRSFamily radio service. Used in the comments or observer fields when the entrant received word about the geyser activity over a radio and cannot identify the observer.
YNMThe code for the seismometer housed in the Norris Museum.
YNBThe code for the co-located seismometer and infrasound station in the Ragged Hills on the western side of Norris Geyser Basin.
YNRThe code for the seismometer just east of Norris Geyser Basin.
YFTThe code for the seismometer nearest to Old Faithful.