Book contents
- Frontmatter
- Dedication
- Contents
- Preface
- 1 Introduction
- 2 Techniques of MOR study: a brief historical review
- 3 The oceanic lithosphere
- 4 Ridges as plate boundaries
- 5 Crustal structure and composition
- 6 Volcanism
- 7 Tectonism
- 8 Hydrothermal processes
- 9 Summary and synthesis
- Appendix A Glossary of terms
- Appendix B Directory of named features
- References
- Index
- Plate Section
7 - Tectonism
Published online by Cambridge University Press: 05 June 2014
- Frontmatter
- Dedication
- Contents
- Preface
- 1 Introduction
- 2 Techniques of MOR study: a brief historical review
- 3 The oceanic lithosphere
- 4 Ridges as plate boundaries
- 5 Crustal structure and composition
- 6 Volcanism
- 7 Tectonism
- 8 Hydrothermal processes
- 9 Summary and synthesis
- Appendix A Glossary of terms
- Appendix B Directory of named features
- References
- Index
- Plate Section
Summary
Introduction
Earthquake focal mechanisms show that MORs are everywhere under tension (Huang et al., 1986). As a result, as soon as young lithosphere is created by magmatic extrusion, intrusion and accretion, the forces of plate separation cause it to fracture (some of these fractures allowing emplacement of new melt – Chapter 6). This fracturing results in a wide range of tectonic features, from tensional fissures less than 1 m wide, through normal faults with horizontal and vertical offsets of tens to hundreds of metres, to detachment faults that cut right through the lithosphere and have offsets of several kilometres. Many of the characteristics of these fractures depend on the spreading rate through its effect on the thermal structure and hence rheology of the lithosphere.
Fissures
The smallest scale of fracturing occurs right at the ridge axis and consists of tensional fissures. The distributions of fissures have been mapped, amongst others, by Crane (1987) using deep-towed side-scan sonar and Haymon et al. (1991) using a towed camera system. Many aspects of fissuring were reviewed by Wright (1998).
- Type
- Chapter
- Information
- Mid-Ocean Ridges , pp. 163 - 199Publisher: Cambridge University PressPrint publication year: 2013