Joanne Baker

Slip Sliding Away

GEOPHYSICS During earthquakes, very high stresses within the crust press the two sides of the fault together so hard that they should be effectively locked together by friction. In the laboratory, rocks are similarly difficult to rip apart. Yet in the landscape setting, faults rupture suddenly and

Mantle Melting Mechanisms

GEOCHEMISTRY During Earths history, heavy metals gradually decoupled from silicate rocks and sank toward the core, which became differentiated from the overlying mantle. Signatures of this process can be traced in the distribution of highly siderophile elements (Re and the platinum group elements

ASTROPHYSICS: Blast Wave Bounce

ASTROPHYSICS On 27 December 2004, a magnetic star, or magnetar, erupted. This event generated a huge burst of gamma rays that were spotted by gamma-ray and x-ray telescopes. In a fraction of a second, the magnetar SGR 1806–20 gave off as much energy as the Sun does in a quarter of a billion years. The energetic blast released by the star was sufficiently large for the generated gamma rays to affect Earths environment when they arrived, causing ionosphere disturbances measured by radio receivers. Mandea and Balasis have found that currents set up in the ionosphere by the crashing gamma rays briefly upset Earths magnetic field. The records of the CHAMP and DEMETER satellites contain a faint ringing signal of the magnetars explosion with a period of 7.5 s for the duration of the flare. — JB Geophys. J. Int. , 10.1111/j.1365-246X.2006.03125.x (2006).