Images: Listening Closely to 'See' Into the Earth
Revealing the plume beneath Hawaii The Hawaiian Island chain was formed by a plume of hot, buoyant rocks from the mantle, but scientists know little about it. 1. To determine the plume’s depth, width, and temperature for the first time, scientists plan to deploy 35 ocean-bottom seismographs. 2. The OBSs will record earthquake-generated seismic waves traveling through the plume, revealing new insights on how mantle plumes work. (Jayne Doucette. ) 3.
A vanload of new WHOI “D2” ocean-bottom seismographs is readied for field testing. The D2s are small and light, for easy deployment and recovery. With a six-month battery capacity, they are designed for relatively short-term experiments. The D2s are available to scientists through the newly created National Ocean-Bottom Seismograph Instrumentation Pool. WHOI Senior Engineer Ken Peal, who helped design the D2, is in the background. (Photo by Victor Bender, Woods Hole Oceanographic Institution)
The D2’s electronic data logger (above), which records seismic wave measurements, resides in a glass ball in one half of the peanut-shaped D2. Batteries are in the other half. (Victor Bender.)
A D2 is field-tested on the seafloor near the TAG hydrothermal vent site in the North Atlantic. A weight anchors it to the bottom. The seismometer is housed in the silver canister at right. (Rob Reeves-
WHOI is designing and building new-generation ocean-bottom seismographs (OBSs) for long-term deployments of more than a year. The four orange fiberglass “hardhats,” mounted on a plastic grillwork, contain batteries and electronics. A differential pressure gauge measures earthquake-generated waves in the water. The seismometer is housed in a metal sphere attached to an swivel at right. When the OBS is deployed, a line corrodes, positioning the seismometer on the seafloor. (Jack Cook.)