Investigation of Subsurface Magma Feeders Taryn Serwatowski Dr. Sven Morgan Department of Geology CMU

Introduction  One type of magma intrusion is called a laccolith  The current model for how laccoliths form involves vertical magma “feeders” called dikes  In this model, magma pushes its way through a crack and then spreads horizontally between layers of rock and creates a dome shape  We think the TML was fed by a horizontal feeder

The Trachyte Mesa Laccolith Top of dome

Background: Evidence of horizontal magma flow  The TML lies along an axis that can be traced directly back to Mt. Hillers  Magma flow direction and minerals are also aligned along this same axis  Both igneous bodies are of the same age and have the same chemical composition

Mount Hillers Area of Research Trachyte Mesa

Traverses 900 ft

Why collect our data here?  The area is directly between Mt. Hillers and the TML  The area is flat lying  There are overlying layers of sedimentary rock

Methods: How we acquired our data  Seismic Reflection and Ground Penetrating Radar were used  Waves sent in the ground reflect back when they strike a subsurface contact  Denser materials will create a high seismic reflection  A seismograph at the surface recorded the image of each wave How seismic reflection works

Acquiring Seismic Data

Anomalies found on 2 nd traverse

Anomaly found on 3 rd traverse

Anomalies found on 4 th traverse

Map x x x x x X Mt. Hillers

Results  Presence of highly reflective interfaces detected  Calculated depth to reflectors correlates with hypothesized depth  Reflectors oriented in line between the laccolith and Mount Hillers  These anomalies also correspond with magnetic anomalies along the same traverses

Conclusions  Not all laccoliths may have formed from vertical feeders  Studying the Trachyte Mesa can provide clues to how magma travels through the subsurface  Strong evidence exists for a subsurface connection between the TML and Mt. Hillers  Seismic Reflection supports theory of horizontal magma feeders  GPR data proved to be unsuccessful  A future survey using a hammer blow at each geophone could result in more reliable data

Questions? Investigation of Subsurface Magma Feeders