Presentation via Zoom By Courtney J. Sprain, University of Florida

Title: Magnetic to the core: A brief introduction to the study of geo- and paleomagnetism

Host: Science Council's MagX Presentation

Discussion Leader: Greg Boebinger

Abstract: Earth’s magnetic field is a fundamental but largely invisible feature of our planet, and we knowingly and unknowingly interact with it in many ways in our daily lives. The magnetic field has been utilized for navigation for centuries, and additionally the magnetic field forms our magnetosphere, which protects Earth’s surface, including our technological infrastructure, from harmful solar storms and cosmic radiation. Despite being a fundamental feature of our planet, our understanding of Earth’s magnetic field is incomplete.

Currently, there are many gaps in our knowledge including:

1. what drives the magnetic field,
2. when did the magnetic field originate,
3. how has magnetic field behavior changed through time, and importantly
4. how will Earth’s magnetic field vary in the future?

Fortunately, we can turn to the geologic record to answer some of these questions.

Fe is one of the most abundant elements on Earth and as such magnetic minerals capable of carrying a remanence over millions of years, such as magnetite and hematite, occur in almost every geologic setting. These minerals interact with the geomagnetic field and once they are incorporated into rocks, either by the cooling of molten lava or deposition and solidification of sediments, they capture a snapshot of Earth’s magnetic field behavior.

By studying the magnetic signature recorded in rocks, we can reconstruct the behavior of the magnetic field going back in time. However, there are many challenges to this work, the largest being the imperfections of naturally occurring magnetic minerals. For synthetic magnetic materials, it is possible to control properties, such as grain size, in order to create an optimal magnetic recorder. For geologic materials, instead we are at the mercy of natural processes which do not always create perfect magnetic recorders. Additionally, we are at the mercy of geologic time, where the rocks we work with have been sitting at Earth’s surface for millions to billions of years in the presence of the geomagnetic field. In spite of these challenges, we have been able to discover a lot about Earth’s magnetic field through paleomagnetic study. In this presentation, I will give a quick overview of these topics, highlighting how paleomagnetic research UF is helping to unravel the history of our planet.