Lava Zone Change?

[ckg]

With the most recent lava flow near Pahoa town, did the lava zone locations change? I had heard from a friend that the maps have been revised but I can not find seem to find anything official to corroborate that so not sure if what he is saying is accurate or tall tale.

[dakine]

Why would they change? If you are at the vents (along the rift zones - Leilani/Kapoho) you're in zone 1. If you are in an area immediately adjacent to the vents (Pahoa/all points south of the East Rift Zone) you're in 2. If you are in an area that lava flows will inundate during a long lived eruption (HPP and all the other Puna subdivisions) you're in zone 3.

More precisely (from HVO's website at http://hvo.wr.usgs.gov/hazards/lavazones/main.html):

• Zone 1: Includes the summits and rift zones of Kilauea and Mauna Loa where vents have been repeatedly active in historic time.

• Zone 2: Areas adjacent to and downslope of active rift zones.

• Zone 3: Areas gradationally less hazardous than Zone 2 because of greater distance from recently active vents and/or because the topography makes it less likely that flows will cover these areas.

• Zone 4: Includes all of Hualalai, where the frequency of eruptions is lower than on Kilauea and Mauna Loa. Flows typically cover large areas.

• Zone 5: Areas currently protected from lava flows by the topography of the volcano.

• Zone 6: Same as Zone 5.

• Zone 7: 20 percent of this area covered by lava in the last 10,000 yrs.

• Zone 8: Only a few percent of this area covered in the past 10,000 yrs.

• Zone 9: No eruption in this area for the past 60,000 yrs.

A good map is at: https://en.wikipedia.org/wiki/Lava_Flow_...rd_Map.png

[PaulW]

I thought they might change too, after seeing lists like this:

http://www.daylum.com/HawaiiRealEstate/h...-maps.html
Zone Percentage of area covered by lava since 1800 Percentage of area covered by lava in last 750 years
1 greater than 25 greater than 65
2 15-25 25-75
3 1-5 15-75

But as I understand it, those percentages are more descriptive than defining.

[dakine]

Why would they change? What about the lava flow into the Pahoa area would facilitate a change? The lava has stayed within zones 1 and 2 and has behaved as described in the zone definitions. To even imagine that the current activity would cause a realignment of the zones is a clear indication of not understanding the lava zones and how they are defined.

And besides, reading rewritten stuff on a realtor's website when the actual data from the authors is publicly available seems pretty silly, don't you think?

For those interested in the real thing, HVO's actual published map, in .pdf file format, and fairly large so as to see detailed land divisions, is linked to here:

https://pubs.usgs.gov/mf/1992/2193/

with the actual map itself here:

https://pubs.usgs.gov/mf/1992/2193/mf2193.pdf

and you will note that even the boundaries of each zone are fairly wide and noted as such:

Hazard-zone boundaries are approximate and gradational. These boundaries are not specific enough to determine the absolute degree of danger at any particular site. Lava-flow hazard maps are designed to show relative hazard across the Island of Hawaii and are meant to be used for general planning purposes only.

[HereOnThePrimalEdge]

What I would like to see is a new set of "Blue Line" maps that show the likely path of a lava flow. The current maps are from 1984 (I believe) and every time the lava fills in low areas, or a lot is graded to remove the gullies, ridges and small hills, the path of a subsequent lava flow will be affected. Admittedly, the Blue Line maps are at best an estimation of the topography in an area, and lava is nothing if not unpredictable, but during the flow of 2014 the lines provided a rough guide, and seemed to me to be fairly accurate a day or two in advance.

Oscar Wilde's Last Words: "Either this wallpaper goes, or I do."

[kalakoa]

[i]a new set of "Blue Line" maps that show the likely path of a lava flow[i]

I would like to see a set of "green line" maps that show the available bailout dollars for different areas.

[PaulW]

Well, if the the lava zones were *defined* by the percentage covered by lava in the last 250 / 750 years then the zones could indeed change every time the lava flows. But, that is not the case. That table, which I have often seen, can lead one to think that is how it is defined but instead it's more of a description.

There, did I explain that simply enough for you to understand?

Lava zones aren't likely to change any time soon, but they could if an entirely new vent opens up.

[dakine]

Lava zones aren't likely to change any time soon, but they could if an entirely new vent opens up.

Wrong again. The lava zone map takes into account all the areas where new vents are likely to happen. Again, this is another example of a serious lack of understanding of the zone designations as well as the volcanic structure and its behavior.

Now if it was said that "they could if an entirely new vent opens up in an unpredictable area outside of the summit and rift zones of the volcano then yes. But the likelihood of that happening is close to nil, at least not until we have the next catastrophic collapse of the a volcanic edifice itself. Then all bets are off.

[PaulW]

This FAQ explains it:

http://hvo.wr.usgs.gov/hazards/FAQ_LavaF...ne/P1.html

[DTisme]

Thanks for posting the link, PaulW. Really helpful!