The Stability and evolution of triple junctions

• Other Authors: Apotria, Theodore G. (Creator), Gray, Norman H. (Major Advisor), Dehlinger, Peter (Associate Advisor), Geiser, Peter (Associate Advisor), Moran, Thomas (Associate Advisor), University of Connecticut (Degree grantor)
• Format: Text
• Language: unknown
• Published: University of Connecticut 1985
• Subjects: Antarctic; Bouvet; Antarc*
• Online Access: http://hdl.handle.net/11134/20002:860656393; https://digitalcollections.ctstatelibrary.org/islandora/object/20002%3A860656393/datastream/TN/view/Stability%20and%20evolution%20of%20triple%20junctions.jpg

Triple junction stability, as introduced by McKenzie and Morgan (1969)> assumes constant relative velocities and can only be defined instantaneously. Factors that affect the stability of triple junctions as a function of time include changes in the boundary orientations and relative velocities. Changes in the velocity triangle can be induced by the effects of motion on a sphere, and the motion of the lithospheric plates with respect to the mantle. Each type of triple junction has been assigned a number of degrees of freedom, where a degree of freedom is an imparted change in boundary configurations or relative velocities without upsetting the stability condition. The number of degrees of freedom correlates positively with the junction's ability to maintain stability under imposed changes. The exact stability condition of any triple junction can be calculated by least squares analysis. An equation for the location of the triple junction with respect to each boundary is introduced with respect to any reference frame. The equations are linear and of the form J = a + hh. A unique simultaneous solution results if the junction is stable. If the junction is unstable, the sum of the squares of the residuals is proposed as a measure of the degree of geometric instability. This analysis is particularly useful when several boundary types are consistent with a single velocity triangle. The type least affected by imposed changes can be regarded as the most geometrically stable, and can be considered in evolutionary schemes. The absolute motion of the Bouvet triple junction with respect to the mantle (mesosphere) plays a significant role in its evolution. Absolute poles of rotation from the AM1-2 model (Minster and Jordan, 1978) for the South American, African, and Antarctic plates were utilized to calculate an "isosceles line" in the South Atlantic. Along this locus (trending 91°)* the relative velocity triangle for the three plates is isosceles. The actual Bouvet triple junction lies about 5 degrees north of this line, ...