By Dr. Robert Thorson

How can I use it? Will it harm me?

These two basic questions lie beneath all land-use decisions.

Humans live wherever the benefits of using the land for habitat, resources or disposal outweigh the risk of being harmed by the land. This is smart.

But there are three problems associated with evaluating the potential for harm. First is the tendency to quickly forget catastrophes such as major hurricanes, tsunamis, river floods and earthquakes that repeat at a time scale of decades or longer. A second, more humbling problem is how stunningly ignorant we can be about how complex the earth is in some situations. Thirdly, how we use the land can decrease or increase the potential for harm.

A perfect example of the last point is the unstoppable gush of hot mud oozing out of the ground near Sidoarjo, Indonesia. The media isn’t sure what to call this geological whatchamacallit: Mud volcano? Mud swamp? Mud lake? Mud spring?

For more than three months, a slurry of steaming, stinky mud has been flowing out of the ground in the vicinity of a natural gas and petroleum well field. The homes of 8,000 to 10,000 people have been submerged by a wet silicate pudding up to 20 feet deep, from which bubbles of hydrogen sulfide are belching to the surface. Factories, farms and roads have been destroyed. Roads have been drowned. People are confused. The stuff keeps coming. Nobody seems to know what to do.

An exploration company was in the process of boring deep (2 miles) into the earth in a search for natural gas. Then came a small earthquake. A few days later, something noxious began to ooze up out of the earth at the drilling site. The company, Lapindo Brantas, has accepted responsibility, and is beginning to compensate those affected.

Unfortunately, local scientists and engineers haven’t been able to stop the hemorrhage, which bleeds at a rate of about 1.75 million cubic feet per day. As the sun-baked, fissured, smoke-puffing surface of the mud lake rises, the dikes designed to hold it back are failing. And with the rainy season approaching, the problem will only get worse, chemically and physically.

Nearby residents were using the land principally as a place to live, work and farm. They did so knowing that this part of Java is prone to volcanic eruptions, earthquakes and landslides.

In contrast, Lapindo Brantas was poking holes in the landscape, hoping to extract a commodity for sale. Only then did things go awry, though the relationship between the drilling and the mud eruption is still not clear. Nevertheless, human use of the land always leads to change, whether it’s visible or not, whether we understand it or not.

Let’s start with a simple example. Consider a Neanderthal living in a cave. The advantage of shelter offsets the risk of getting clobbered by stone falling down from the cave roof. Depending on circumstances, however, the presence of humans may increase (by breathing) or decrease (by fire) the moisture level in the cave, changing the stability of the roof for better or for worse.

Now consider the much more complex case of drilling through wet, porous layers of fine-grained oceanic sediment full of sulfur- bearing organic remains that are being flexed and thrust downward into the earth by tectonic forces. Meanwhile, nearby volcanoes are producing all manner of solids, liquids and gases, which squirt around below the surface.

Pressures rise. Temperatures rise. Gas from exhaling volcanoes mingles with gas from decaying organic materials. Petroleum, boiling water, lava and crystals of clay move around until trapped. Rock fractures open and close. The squeeze continues.

Then this underground cauldron was tapped. Was it a seismic shift in the crust — possibly provoked by drilling — that initiated fluid movement and mud liquefaction? Or did the drill hole puncture some barrier? Scientists don’t yet know. What they do know is that the mud chose the well field as a means of escape from below.

We should be careful when messing around with the Earth. As the philosopher and statesman Sir Francis Bacon (1561-1626) once remarked, “Nature, to be commanded, must be obeyed.”