September 5, 1997

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.

Lava's not fire

"A curtain of fire extended far down the rift zone. Fire fountains played to great heights. Burning embers fell to the ground. Smoke drifted downwind from the fountains of fire. Rivers of fire flowed downslope."

Most readers will recognize the description of a Hawaiian eruption. They will also acknowledge, though perhaps only unconsciously, how inaccurate that description really is. Fire and smoke are words often used in connection with eruptions, but the words are rarely accurate. Colorful metaphors, perhaps, but they are not useful for understanding the eruption and not even necessary for visualizing the events.

Volcanology is replete with reminders of its nonscientific past. Ash, cinders, the term igneous (referring to rocks once molten, from the Latin ignis, meaning fire), even volcano itself (from the Latin god of fire, Vulcan), are some of the technical words used today by scientists that derive from a time when fire was considered one of the primal elements and volcanoes were ovens or hearths above the fiery interior of the world. This lack of understanding transcended cultures. Fire was considered responsible for, and indeed synonymous with, lava.

There was some logic to this. Fires are hot, and so is lava. Flame is orange, and so is lava. Fire is mesmerizing, and so are eruptions. Both fire and eruptions were viewed as mysterious natural sources of heat that must somehow be related.

But we have made progress in understanding nature. We now know that lava (and its underground equivalent, magma) is formed, not by burning anything, but by slow heating under great pressure within the earth. There are several sources of the heat - chemical reactions, radioactive decay, residual heat left from the formation of the planet, to name a few - that in combination with the pressure can cause rocks to melt in the earthís crust and especially the underlying mantle. Some of the melted rock, magma, rises buoyantly to the surface and erupts as lava, and some is trapped underground, cools slowly, and forms rocks such as granite.

It is clear today that we should avoid confusing fire with lava. This is a problem that all of us - volcanologists, interpreters of natural science for the public, and you, the general public - need to work on. We scientists are stuck with having to use technical words such as ash, cinders, and igneous, but words such as fire, smoke, embers, and burning do not apply to eruptions (unless, of course, vegetation or buildings were actually ignited by the eruption.)

As an example of how correct words can substitute for misleading metaphors, the introductory paragraph of this column can be rewritten:

A row (or curtain) of fountains extended far down the rift zone. Lava fountains played to great heights. Glowing spatter fell to the ground. Fume drifted downwind from the fountains. Rivers of lava flowed downslope.

Kilauea Eruption Status--September 5, 1997

During the past week, there was constant effusion of lava from the crater cone vent within Pu`u `O`o. Through a network of tubes, the lava flowed down to the seacoast where it entered the ocean at four locations. Two of the ocean entries are located at Waha`ula, and two are located in the area of Kamokuna. The public is reminded that the ocean entry areas are extremely hazardous, with explosions accompanying frequent collapses of the lava delta. The steam cloud is highly acidic and laced with glass particles.

Recent Big Island Earthquakes

There were no felt earthquakes reported during the week.