Reventador, located in northern Ecuador, is an active volcano. In 2002 it erupted with such massive force that it blanketed Quito, Ecuador's capital city 60 miles to the west, with a layer of ash so thick the airport had to shut down.

Today it blows its stack with lesser force but with great frequency. And just as storm chasers want to be where the cows are flying around, volcanologists want to be as close as they can get to 11,500-foot peaks that spew grapefruit-sized molten rocks several times a day.

What scientists want even more than taking in the sights and sounds, however, is gathering precise records of seismic activity and studying the data, which is where Matt Welsh, assistant professor of computer science at Harvard University, and his wireless sensor mesh network come in.

Previously, seismologists from the University of New Hampshire (UNH) and University of North Carolina (UNC) collected data by lugging bulky, heavy sensor stations up the mountain - each one containing a car battery for power plus sensors, cables, and data logging and data storage equipment.

Every few days someone had to trek several hours back up the mountain to collect the microdrives. This put severe limits on the number of sensor stations deployed and consequently on the amount of data collected. The setup also had other limitations - for example, there was no way to tell if one of the stations had stopped functioning.

Welsh had a better idea. He had a 190-node wireless sensor mesh running at Harvard that was designed to detect changes in a building's temperature and humidity. Now it was time to bring his mesh network out of the lab and into the line of fire.

It's a jungle out there

For the Reventador expedition, Welsh created a tiny, low-power sensor station that runs on ordinary D-cell batteries and fits into a plastic case the size of a lunchbox. It sends seismic and sonic data around the clock to a base station that collects data in real time. Total cost: $400 per node.

In August 2005, the seismologists from UNH and UNC and the computer scientists from Harvard flew to Quito, drove three hours, then bushwhacked through the jungle for several hours to the base of the mountain, where they camped. At 5 a.m., Reventador issued a loud wake-up call.