Day: May 29, 2007

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Observations for 29 May

For the wait for yesterday (28 May) evening's eruption of Grand, the sky was dark and overcast to the west, while clear to the east. The wind was still as blustery and annoying as earlier in the day. As I waited, the gray got darker, and eventually, it started to snow wet, fat flakes. But at the same time, it began to lighten to the west, so that the disk of the sun could be made out. The shower was colored pink by this low lighting. By the time the shower ended, the sun would have been visible if it hadn't just set. That's when Grand erupted. It would have been a very pretty eruption if it hadn't been so steamy and windy.

The overnight Grand was in completely different circumstances. There was still some clouds obscuring a setting moon, but it was dead calm. The boardwalks were still covered with ice from the previous evening's snow. The eruption itself was unremarkable except for the fact that Percolator was dead and there were two bursts.

On to Giant afterwards, where it was obvious from the platform that there hadn't been a hot period in a few hours. Also, it appeared that Grotto was once again going into a marathon eruption. The platform also reflected this, as Bijou was chaotic in its behavior, and all the features seemed weak.

I placed my thermometer outside the cabin when I came back in at 06:15, and just a few minutes later, it read 29°F. Which means it was much colder out in the basin itself.

Of course, the problem with making plans based on what you think the geysers are going to do is that the geysers might have other plans. When I got out for the late morning Grand eruption, it was obvious that Grotto had quit. So no marathon, and it appears I'm going to have to drop some of the errands I'd planned for today.

So just as I'm about to post the above, the call goes out that "there's water rising in Mastiff". So at 11:18 we get an 8m25s hot period, and I get to add some exercise I hadn't intended.

Other Geyser Times

28 May 2007

  • Grotto Fountain 18:57 w/o Grotto
  • Rift 21:07ns

29 May 2007

  • Penta 06:31ie, steam phase
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Observations around Giant


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Catfish Geyser and erosion

One of the first things I noticed at Giant was the amount of erosion in two areas. In the first, the edge of the platform northwest of Feather and the rest of the sputs has been eaten back by what seems to be over a meter in places. This area of fresh, unweathered sinter is distinctly terraced.

Over by Catfish, the whole front of the base of its cone also shows fresh, laminated sinter which, I would assume, is being exposed and undermined by the action of Mastiff during both eruptions and hot periods.

If this is what frequent activity over a few years time can do, the the question, it seems to me, becomes, how long until a major change in one of these features occurs because of this erosion. One of the sput vents could have it's rim dropped by several centimeters. The whole southwest side of Catfish could be opened up and exposed, turning it into another breached cone just like Giant.

Another possibility is that the deposits within the actual vent of Catfish do not have the horizontal laminations characteristic of all the erosion going on, and thus will be more resistant to the attack on it.

Perhaps erosion plays a larger part in the formation of cones than is realized. A feature builds up a modest raised vent in the middle of a larger, flat platform. Then another feature erodes away those horizontal platform deposits, leaving the vent's vertical deposits intact. The second feature subsides, allowing the first feature to continue to build deposits on its cone, but now outside over the newly exposed platform. Eventually, it might be difficult to determine that the platform was ever much higher, and the cone not as tall.


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Turtle Geyser cone

A perfect example of this is not far away: Turtle. Note how the turtle shaped cap is sitting on a horizontally laminated pedestal. If it were to reactivate and begin depositing over the entire structure, evetually those laminations would be hidden and instead we would see a tall cone there.