Application | Volcano
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CABLES TO THE CRATER Hekla is one of Iceland’s most active volcanoes. Scientists hope to use a network of seismometers to peer into the belly of the mountain and warn of an impending eruption. Connecting this network calls for an especially tough cable from LAPP, as the environment in the mountains of Iceland is anything but friendly. /////////////////////////////////////////////////////////
DETECTING THE WARNING SIGNS Möllhoff’s team is in the process of installing six seismometers on top of Hekla. Each of these metal cylinders contains a mass made from a thermally stable metal alloy. This is kept virtually motionless by means of an electronic feedback loop. Tremors in the ground cause the housing to vibrate, while the mass does not follow the motion due to its inertia. The position of the mass relative to the housing is measured and the feedback loop executes a magnetic or electrostatic counterforce, depending on the model. The voltage required to generate this force is the measurement value that is digitally recorded. This makes it possible to detect movements of just a few nanometers (1 nanometer = 1 millionth of a millimeter). As Hekla offers so little warning time, it is not possible to save the measurement values in the seismometer and take readings on site every few months as usual. Instead, they must be communicated immediately. This usually occurs via 3G mobile modems, but is not possible for all six seismometers as the modem requires up to five watts of electrical power. In the gloomy Icelandic landscape, where the sun only rises for a few hours a day — if at all — in winter, solar cells cannot provide enough energy. That is why Möllhoff’s team decided to use a cable from LAPP to transfer the data. This cable transfers not only the data but also the power required to run the seismometers, which is generated by three independent small wind turbines. Each turbine is supported by a solar cell to compensate for periods of low wind in summer. The aim is to keep overall energy consumption as low as possible. The cable was supplied by Johan Rönning, the market leader for electrical equipment in Iceland. Johan Rönning imports and sells LAPP products in Iceland, and supplies electrical components to most geophysical installations. The company has been working with LAPP since 1985. “We are very happy with the cooperation,” says Óskar Gústavsson, key account manager at Johan Rönning. Gústavsson praises the excellent support from LAPP’s experienced experts: “They’re also fantastic with delivery times.” ACROSS RAZOR-SHARP VOLCANIC ROCK The distances between the wind turbines, data transfer centers, and the seismometers are relatively short. The scientists were able to order
The equipment, including 3,000 m of cable from LAPP, was transported through ice and snow up the slopes of the Hekla volcano in Iceland. Source: Icelandic Meteorological Office
Volcanoes are just as much a part of Iceland as geysers, elves, and trolls. One of the most active and dangerous of these is Hekla, located in the south of the island. It erupts approximately every ten years, most recently in 2000, spewing fountains of ash 18 miles into the sky. But since the last eruption, the volcano appears to have been on a break. This is good news for tourists, who have come in droves to hike to the crater rim 4,892 feet above sea level. But this makes geophysicists nervous. “Hekla could erupt at any minute,” warns German geophysicist Martin Möllhoff, “and the longer this quiet period goes on, the more violent the eruption will be.” Möllhoff works at the School of Cosmic Physics of the Institute for Advanced Studies in Dublin, Ireland. Here, he leads the technical division that uses seismometers to monitor countless volcanoes around the world, including Hekla. If these probes detect minor tremors in the ground, it is red alert. This is because the last eruptions were only detected 30 to 80 minutes in advance. To ensure safety on such short notice, all visitors to Hekla must download an app which receives warning messages via SMS.
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