In September 2005, a sixty-kilometer crack opened in the Ethiopian desert in days, swallowing several hundred years of tectonic motion in one event.
Documented
The dike, measured
Between September 14 and October 4, 2005, a 163-earthquake swarm announced the intrusion of a roughly sixty-kilometer-long dike beneath the Dabbahu and Manda Hararo segment, with a maximum opening of about eight meters. Geodetic inversion put one to two cubic kilometers of magma into the crust in under two weeks, most of it arriving laterally, without a matching eruption at the surface.
Assessment: Documented by satellite radar interferometry, seismology, and fieldwork: the largest dike intrusion ever measured on land.
Stories
Centuries in a fortnight
The popular read was a freak crack. The geological read was worse and better: rifting is punctuated, not smooth. Long quiet centuries of strain get paid off in violent two-week events, which means slow plate-motion averages hide the true rhythm. The 2005 event kicked off a five-year episode of at least seven more dike intrusions along the same segment.
Assessment: Stories: the crack was not the anomaly. The calm between cracks is.
Interesting claims
The balloon model
Ebinger's own framing: the crust is a balloon being overfilled by magma, and the science question is the straw that breaks the camel's back. Rifting is a pressure event with a schedule nobody can read yet.
Assessment: Interesting: the mechanism that splits continents behaves less like erosion and more like an aneurysm.
Sources and further reading
Keir et al., 2006, on the 163-event M>3.9 earthquake swarm and 60-km dike of September 2005
Grandin et al., JGR 114:B07402 (2009): 1.5-2.0 cubic km dike, faults slipping 3 m, lateral magma injection
Cynthia Ebinger, via National Geographic and USA Today: several hundred years of plate movement in a few days
Wright et al., Nature (2006) and Ayele et al. (2007, 2009) on the 2005-2010 Dabbahu-Manda Hararo rifting episode
Worth asking
If continents tear in sudden jerks instead of slow drifts, what else about gradual Earth is a sampling illusion?