Explore the intricate connections between earthquakes, rock compositions, and volatile elements in the Earth's mantle transition zone through this comprehensive AGU Fall Meeting Birch Lecture. Delve into global tectonics as presented by W. Chen from the University of Illinois, Urbana, covering topics such as travel time curves, the Tonga Subduction Zone, petrologic effects, and global subduction zone studies. Gain insights into seismic slabs, GPS data interpretations, and hydroxyl reduction processes. Analyze real data, examine current configurations, and understand the complex relationships between various geological phenomena in this hour-long presentation that offers a deep dive into the Earth's internal dynamics.