The Influence of Magma Supply and Eruptive Processes on Axial Morphology, Crustal Construction and Magma Chambers
Abstract
This Thesis examines the influence of magma supply and eruptive processes on axial morphology, crustal construction, and the properties of crustal magma chambers at mid-ocean ridges. Variations in magma supply over ^ 100 Kyr generate along-axis changes in crustal thickness and temperature. Magma sill properties and hydrothermal activity are linked to spreading events which occur on much shorter time scales (ca 10-100 yr). The observed magma sills lie considerably deeper than the level of neutral buoyancy. Magma ponds beneath mid-ocean ridges at a thermally controlled permeability boundary. Thermo-mechanical models predict that rift valley and magma sill formation are sensitive to small changes in crustal thickness and mantle temperature. Gravity reveals small differences in crustal thickness and mantle temperature accompanying a change from axial high to rift valley. A stochastic model for the emplacement of dikes and lava flows, with a narrow dike intrusion zone and a bimodal distribution of lava flows, satisfies geological and geophysical constraints on the construction of the extrusive section. This Thesis underlines the importance of eruption dynamics in the emplacement of the uppermost volcanic layer and of the crustal thermal structure in controlling local variations in magma sill depth and ridge morphology.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1997
- Accession Number
- ADA331709
Entities
People
- Emilie E. Hooft
Organizations
- Massachusetts Institute of Technology