We will then focus on the Vema fracture zone at 10°–11° N, where a We will consider in particular lithosphere generation occurring along the northern MidĪtlantic Ridge (MAR) from Iceland to the equator, including the formation of trans-įorm offsets. Sphere is generated along mid-ocean ridges due to upwelling of convecting hot mantle. We will review the processes leading to the generation and evolution of theĮarth’s lithosphere that lies beneath the oceans. The lithosphere is the external, mostly solid and relatively rigid layer of theĮarth, with thickness and composition different below the oceans and within the con. Tinents and ancient stable ocean basins to one with wandering continents and young,Īctive ocean basins, reviving Wegener’s Continental Drift that had rested dormant for Half a century ago, our view of the Earth shifted from that of a Planet with fixed con. Multiple boundaries develop so that strike-slip ruptures avoid very thick and strong lithosphere. Numerical modeling predicts the development of wide multiple transform boundaries when the age offset is above a threshold value of similar to30 m.y., i.e., in extra-long (>500 km) slow-slip transforms. Some of these events may be triggered by earthquakes from the principal boundary. However, strike-slip seismic events also occur in the second valley and elsewhere in the deformed zone. One of the valleys is seismically highly active and constitutes the present-day principal transform boundary. Examples are the 750-km-long, 120-km-wide Andrew Bain transform on the Southwest Indian Ridge, and the Romanche transform, where the Mid-Atlantic Ridge is offset by a lens-shaped, similar to900-km-long, similar to100-km-wide sliver of deformed lithosphere bound by two major transform valleys. However, we define here a new class of oceanic transform boundaries, with broad complex multifault zones of deformation, similar to some continental strike-slip systems. Multiple boundaries develop so that strike-slip ruptures avoid very thick and strong lithosphere.Oceanic transform plate boundaries consist of a single, narrow (a few kilometers wide) strike-slip seismic zone offsetting two mid-ocean ridge segments. Numerical modeling predicts the development of wide multiple transform boundaries when the age offset is above a threshold value of ∼30 m.y., i.e., in extra-long (>500 km) slow-slip transforms. Examples are the 750-km- long, 120-km-wide Andrew Bain transform on the Southwest Indian Ridge, and the Romanche transform, where the Mid-Atlantic Ridge is offset by a lens-shaped, ∼900-km- long, ∼100-km-wide sliver of deformed lithosphere bound by two major transform valleys. Oceanic transform plate boundaries consist of a single, narrow (a few kilometers wide) strike-slip seismic zone offsetting two mid-ocean ridge segments.
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