Research by Technique
Sea Surface Magnetic Field Studies
Sea surface magnetometers towed behind ships have been used to measure
the magnetic field of the ocean basins since the Second World War. The magnetic field measured
in this way typically show a characteristic pattern of magnetic stripes or anomalies that are
often symmetrically arranged each side of a midocean ridge spreading center. Just after
reversals in Earth's magnetic field were discovered in terrestrial lavas in the early 1960's,
Fred Vine and Drummond Matthews (1965) published a classic paper that suggested that the
igneous rocks of the ocean basins could also record these reversals and that the magnetic
anomaly stripes were a recording of earths past magnetic field behavior. It turns out
that the average depth of the ocean basins is just enough to filter the seafloor magnetic
signal to produce a easily observed wiggle signal at the sea surface.
Click on navigation buttons on left side for specific magnetic projects.
Deeptow Magnetic Field Studies
The spatial resolution of sea surface magnetic surveys is limited
by the depth of the oceans, typically on the order of 2 to 4 km. Thus, shorter
wavelength anomalies are often not well resolved. Deeptow magnetic surveys offer
the opportunity to improve our resolution by towing a magnetometer near the
ocean floor. Typical spatial resolutions are on the order of a few hundred
meters. Along with this improved spatial resolution comes high amplitude and
greater "noise" from topographic variations and towfish undulations.
Submersible Magnetic Field Studies
Submersible magnetic field mapping offers the highest resolution
of magnetic surveys. My work has focused on using this kind of data for very
specific types of problems. An important problem concerns the vertical structure
of oceanic crust and what part of the crust is responsible for creating magnetic
anomalies. I led an ALVIN cruise (BLANCOVIN) to the Juan de Fuca Ridge to
look at a steep scarp wall at the Blanco Fracture Zone. Some links to past
projects are shown below
ROV and Autonomous Underwater Vehicle Magnetic Field Mapping
We are also
using ROV and Autonomous Underwater Vehicles (AUV) to map the
high resolution magnetic field over seafloor features to look at very young
crust and how the magnetism changes over time. Also high-resolution
magnetic field mapping can image the effects of hydrothermal venting
on the ocean crust - by finding areas where the corrosive vent fluid
has demagnetized the crust through chemical alteration.
Along with Dan Fornari and the Deep Submergence Lab, WHOI also operates
a 4-barrel 1-m ROV-mounted drilling system originally built by MBARI but now available to the
science community through an NSF shared-used facility.
© Woods Hole Oceanographic Institution. All rights reserved