Convergent Margin Comparison

Title: Convergent Margin Comparison
Description: Landforms - Though these margins are both convergent, they exhibit somewhat different landforms. The Cascades consist of many more stratovolcanoes, indicative of more siliceous magma and more viscous magma. This is due to the difference in the thicknesses of overlying continental lithosphere (thicker at the Cascades).

Geochemistry - Referring to the Harker Diagrams for the Bismarck Arc - New Britain Chain and the Cascades, we see an immediate higher concentration of MgO series in the Bismarck Arc. This is possibly due to the fact that the Cascades sit further inland, allowing for the further evolution of a magmatic body.

According to Alkali analysis, we see an agreement among the data that the margins exhibit a sub-alkaline series, however, the cascades have a higher alkali content than the Bismarck to New Britain Arc - likely due to the same reason listed above (higher amount of continental lithosphere incorporated into the melt).

REE analysis of the convergent margins suggests that the Cascades have a higher concentration of incompatible elements relative to the Bismarck - New Britain Arc.
Creator: Robert Ashton & Devon Leach
Date: May 5th, 2015
Mediator: Tamara Carley