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Mid-Ocean Ridges: Discontinuities, Segments and Giant Cracks

1991; American Association for the Advancement of Science; Volume: 253; Issue: 5023 Linguagem: Inglês

10.1126/science.253.5023.986

1095-9203

Ken C. Macdonald, Daniel S. Scheirer, S. M. Carbotte,

Geological formations and processes

Geological observations reveal that mid-ocean ridges are segmented by numerous rigid and nonrigid discontinuities. A hierarchy of segmentation, ranging from large, long-lived segments to others that are small, migratory, and transient, determines the pattern and timing of creation of new ocean floor. To the extent that spreading segments behave like giant cracks in a plate, the crack propagation force at segment tips increases with segment length, which may explain why long segments tend to lengthen and prevail over shorter neighboring segments. Partial melting caused by decompression of the upper mantle due to plate separation and changes in the direction of spreading result in the spawning of new short segments so that a balance of long and short segments is maintained.