The area affected by the Hawaiian volcano

When reporting the Big Island volcano eruptions, the media rarely mentions the relative size of the affected area to the whole island. Here is the latest map from the USGS which shows the affected area.

On the inset on the map above, you can see that the affected area, in pink, is a small portion of the island. Furthermore, there are only two spots in the affected area with volcanic activity, the Kilauea summit and the Leilani Estates, 26 miles apart.

There are no lava eruptions at the Kilauea summit nor are any expected. There used to be a lava lake at the top of the vent at the summit, visible from an overlook and a big tourist attraction. The activity that we now see at the summit is not caused by lava coming up, but by lava draining down the vent.  Falling rocks and steam from ground water have caused all the eruptions we have seen from the summit.  (The definition of "eruption", allows for a steam explosion without lava). The "Big One", often mentioned in the news, is the hypothetical worse case steam explosion, and may have already happened. No lava flow was ever expected to follow the Big One at the summit.

The lack of lava flow from the summit should not be surprising. Most of the Kilauea eruptions have been along its rift. The rift is the red line in the map inset above. The recent 35 year Kilauea eruption came from the Puu Oo vent on the Middle East Rift Zone, 12 miles from the summit. When the 5.0 earthquake happened on May 3, there was huge pink cloud from Puu Oo. This was caused by rock falling down the vent. There was no lava eruption. Lava had already drained down the Puu Oo vent. Its crater floor had collapse on April 30. There is currently no action at Puu Oo.

The lava eruptions are all contained in an area around Leilani Estates on the Lower East Rift Zone. You can see the size of the eruption area in the inset of the map above; it is the small rectangle on the right. There was nothing surprising about the location; it was classified with a the highest hazard level. The homes were cheap and the insurance was very high. The home owners knew the risks.

The larger part of the map above shows the current lava flows and past lava flows from the Lower East Rift Zone in 1840, 1955 and 1960. You can see that the current flow is normal for the area. The current lava flows came in two phases. The flow from 5/3 to 5/18 was from old magma already in the rift and was sluggish. When a rift opened, there was initial lava splattering and stopped soon after. The flow after 5/19 came from the magma drained from the Middle East Rift Zone. It was more fluid and can be expected to spread, but it does not look like it will exceed past eruptions in the area.

When taken by themselves the two events, the steam explosions at the summit and the lava flows in the Lower East Rift Zone, are not unusual. However, the news reports these event together and made no attempt to stop their audience from conflating them. So one could get the impression that a catastrophic lava explosion is imminent at Kilauea that will affect the whole island. Totally wrong.

There is no imminent catastrophe. There are problems next to the summit and near Leilani Estate. We will be far from either location. The Kona Airport, our Waikoloa condos and Auntie's Honokaa house are all far away from either the Kilauea summit or Leilani Estates. The shortest distance is 48 miles from the Kilauea summit to Honokaa. The longest distance is 75 miles from Leilani Estates to the Kona Airport.

But will the distance protect us from the SO2 gas. The short answer is yes, but requires more explanation and will be the topic of the next blog post.