[Geysers] Union Geyser Refilling Rate

[Jeff Cross]

After reading the accounts of Union Geyser in Hayden's 12th annual report (found online at Google Books), I am intrigued to find that the geyser had a very slow fill rate.

Two eruptive series were seen in 1878.  The 1st series had 3 eruptions (I = 2h50m and 7h05m), and the 2nd series had 2 eruptions (I = 3h11m).  The series start interval was 5d13h01m.

Union required just over 24 hours following the first eruption of the series before water was visible in the center cone.  This was consistent between the two series, even though the 1st series had 3 eruptions and the 2nd series had only 2 eruptions.  I would think that the extra eruption in the 1st series should have delayed the refilling because Union would have to collect an entire extra eruption's worth of water.  But that assumption is wrong here.

It took days for Union to reach a point where it "spurts" or "spouts" "over the edge" (Hayden's terms), 3.6 days after the start of the 1st series and 4.0 days after the start of the 2nd series.  (The meaning of "over the edge" is ambiguous, as it could refer to overflow, or to splashes rising above the cone's rim.)

The refilling rate when the water was between -4 feet and overflow can be calculated from the data presented in the 12th annual report.  The vertical rate of ascent was only 0.06 ft/hr, which works out to 0.7 inches / hour.

My question:

=> Does anyone know of a large geyser with a similarly slow refilling rate?  On the order of days to rise just 4 feet?  <=

If not, then we have one potential hypothesis to explain Union's present state of abject dormancy--the geyser never had much of a water source to begin with.  Whatever change occurred in the late 1970s when Union fell dormant may have been slight.

Compare the slow refilling rate of Union with that of Old Faithful, which can be calculated at around 38 feet/hr (from Hutchinson, Westphal and Kieffer, Geology, v. 25 p. 875, Figure 5A), which strikes me as unusually fast.  But, then, Old Faithful is an unusual geyser, erupting about 10 times as frequently as other geysers of the same size.  I would guess that refill rates of about 1 to 10 feet per hour would be typical of most geysers.  What do you think?

Jeff Cross
jeff.cross at wallawalla.edu