The College of Arts and Sciences

Andrew Horst

PhD Candidate Earth Sciences

Advisor: Jeff Karson

Research and Teaching Interests

My research interests encompass combining tools from structural geology and paleomagnetism to address problems in geology. Primarily, I use both structural analysis and rock magnetic properties to understand deformation of Earth’s crust. I’m also very interested in mid-ocean ridges and other volcanic systems and what’s going on beneath these volcanoes, below the surface lavas and other eruptive products. These are places that we could never directly observe, so there are a number of approaches used to better understand these subvolcanic areas. My approach has been to look at rocks that originally formed in these areas beneath mid-ocean ridge volcanoes that are now exposed in various locations. Some of these rock exposures occur at large fault escarpments on the seafloor due to tectonic forces at propagating rifts, or in subaerial analogs such as in Iceland, where glaciers have carved exposures into older, deeper portions of the crust. I’m particularly interested in the spatial distribution and transport of magma beneath volcanic systems, or how magma flows within the subvolcanic plumbing system. In addition, I would like to better understand deformation that occurs in oceanic crust near the mid-ocean ridge crest, as well as far from this ridge axis where it forms. The implications from these studies range from providing a better understanding of the formation of oceanic crust that covers ~70% of Earth’s surface below the oceans, to determining potential drill sites for geothermal energy, or understanding basin-forming processes and heat flow variations in the deep ocean. Through combining structural and magnetic analyses of modern seafloor and various analogs, I seek to better understand the processes that occur beneath mid-ocean ridges and how these processes may vary along the ridge axis to provide deeper insight into divergent plate boundaries.

My dissertation focuses on structural and magnetic analysis of oriented samples collected from the seafloor and in Iceland to advance our understanding of subaxial seafloor spreading processes and along-axis variations in mid-ocean ridges with high magma supply. I’ve had the opportunity to work on fully-oriented samples of basalt dikes from Pito Deep Rift, a seafloor escarpment in the southeastern Pacific Ocean, collected using Alvin and Jason II submersibles. The goal of this study is to better understand the geologic history from early stages of intrusion and flow of magma to later structural rotations of crustal blocks. Measuring the anisotropy of magnetic susceptibility (AMS) of specimens from block samples reveals the rocks magnetic fabric, as a proxy for the silicate crystal fabric, and offers insight into accretionary processes such as magma flow in these seafloor dikes. By combining additional measurements of paleomagnetic remanence in these specimens with structural data, we can address the style and magnitude of structural rotations within igneous components of the oceanic crust that otherwise lack a reliable paleohorizontal reference. Since these areas on the seafloor are difficult and expensive to access, I am incorporating studies in Iceland to augment of these seafloor studies. I’ve been fortunate to work on a few different projects in Iceland, but my most recent focus has been structural and paleomagnetic analysis of lavas and dikes within a broad transform fault zone in northern Iceland as an analog for deformation in oceanic transform faults, especially those associated with propagating rift systems. By comparing these different studies, I hope to provide a better understanding of the nature and details of accretionary processes and structural aspects of oceanic crust at mid-ocean ridge spreading centers that are not permitted by seafloor surface and remote geophysical studies alone.

Teaching

Spring 2012: Teaching Assistant for Oceanography (EAR 117), Syracuse University, NY

Fall 2011: Teaching Instructor for History of Earth and Life (EAR 102), Syracuse University, NY

Spring 2011: Teaching Assistant for Earth Science (EAR 105), Syracuse University, NY

Fall 2010: Teaching Assistant for Structural Geology (EAR 333), Syracuse University, NY

Spring 2009: Teaching Assistant for Earth Science (EAR 105), Syracuse University, NY

Fall 2008: Teaching Assistant for Structural Geology (EAR 333), Syracuse University, NY

Spring 2007: Teaching Assistant for Processes and Concepts (GEO 200), College of Wooster, OH

Fall 2006: Teaching Assistant for First Year Seminar ‘Science in the Media’, College of Wooster, OH

Publications

Papers:

Horst, A. J., R. J. Varga, J. S. Gee, J. A. Karson (2011), Paleomagnetic constraints on deformation of superfast-spread oceanic crust     exposed at Pito Deep Rift, J. Geophys Res., 116, B12103, doi:10.1029/2011JB008268.

Varga, R. J., A. J. Horst, J. S. Gee, J. A. Karson (2008), Direct evidence from anisotropy of magnetic susceptibility for lateral melt     migration at superfast spreading centers, Geochem., Geophys., Geosyst., 9(8), Q08008, doi:10.1029/2008GC002075.


Conference Abstracts:

Horst, A. J., R. J. Varga, J. S. Gee, J. A. Karson (2011), Paleomagnetic Analysis of Block Rotations in the     Wake of the Migrating     Tjörnes Transform Zone in Northern Iceland, Abstract T23D-2430 presented at 2011 Fall Meeting, AGU, San Francisco,     Calif., 4-9 Dec.

Siler, D. L., J. A. Karson, A. J. Horst, R. J. Varga (2010), Subsidence and basaltic caldera formation  during crustal construction in     Iceland, Abstract T31B-2160 presented at 2010 Fall Meeting, AGU, San Francisco, Calif., 13-18 Dec.

Karson, J. A., D. L. Siler, A. J. Horst, R. J. Varga, D. Curewitz (2009), Toward a Comprehensive View of     Seafloor Spreading:     What’s Happening Under the R2K Study Areas?, Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract OS21B-01.

Siler, D. L., J. A. Karson, A. J. Horst, R. J. Varga, M. Pollock, A. Nanfito (2009), Structure and kinematics of segment-scale crustal     accretion processes in Iceland, Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract OS13A-1165.

Horst, A. J., R. J. Varga, J. S. Gee, J. A. Karson (2009), AMS Constraints on Initial Magma Flow in Sills:     An Icelandic Analog for     Crustal Accretion at Mid-Ocean Ridges, Eos Trans. AGU, 90(52), Fall     Meet. Suppl., Abstract GP43A-0838.

Horst, A. J., R. J. Varga, J. S. Gee, J. A. Karson (2008), Evidence of tectonic rotations and magmatic flow     within the sheeted dike     complex of super-fast spread crust exposed at Pito Deep Rift, EOS Trans. AGU, 89(53), Fall Meet. Suppl., Abstract V43I-04.

Siler, D. L., J. A. Karson, A. J. Horst (2008), The 3-dimensional structure of inclined sheet swarms in Iceland and associated crustal     thickening at Icelandic spreading segment centers, EOS Trans. AGU, 89(53), Fall Meet. Suppl., Abstract GP13A-08.

Varga, R. J., A. J. Horst, J. A. Karson D. L. Siler, J. S. Gee (2008), Rapid subsidence and formation of thick volcanic sections at     magma-rich spreading centers:  Paleomagnetic and AMS evidence from north-central Iceland, EOS Trans. AGU, 89(53), Fall     Meet. Suppl., Abstract GP21D-0801.

Horst, A. J., J. A. Karson, R. J. Varga, J. S. Gee (2007), Models of deformation of uppermost oceanic lithosphere: Comparison of     crustal flexure in the Blönduós area, Northern Iceland, and structure of     East Pacific Rise Crust at Hess Deep, EOS Trans.     AGU, 88(52), Fall Meet. Suppl., Abstract T23B-1411.

Siler, D. L., J. A. Karson, R. J. Varga, A. J. Horst (2007), Internal structure of the extinct Skagi-Hunafloi     Rift Zone, and     implications for magmatic construction, EOS Trans. AGU, 88(52), Fall Meet. Suppl., Abstract T23B-1424.

Horst, A. J., R. J. Varga, J. S. Gee, J. A. Karson (2006), Magnetic remanence and anisotropy of magnetic     susceptibility of dikes     from super-fast spread crust exposed at Pito Deep Rift, EOS Trans. AGU, 87(52), Fall Meet. Suppl., Abstract T51C-1546.

Varga, R. J., A. J. Horst, N. Welty, K. Siegner, P. Ferringer (2006), Paleomagnetism of the Peach Springs     Tuff revisited, Geological     Society of America Abstracts with Programs, 38(7), 352.