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The northern Mid-Atlantic Ridge (MAR) is a classic, slow-spreading ridge with an average spreading rate of ∼25 mm/yr. The MAR is typically marked by a 1.5–3-km-deep, 15–30-km-wide axial rift valley Major transforms offset the ridge along its length. Between the transforms, the ridge is divided into spreading segments; their ends are defined by non-transform offsets. The rift valley commonly contains an axial volcanic ridge that is considered to be the predominant site of volcanic activity [e.g., Ballard and van Andel, 1977]. Based on the sizes of the volcanic ridges [e.g., Smith and Cann, 1999], large volumes of lava must be erupted on the valley floor. Currently, however, it is not known how frequently magmatic events occur, whether they migrate along the axis, whether there are spatial patterns in these events, or how they vary through time.