March 29 @ 4:00 pm - 5:00 pm CDT
Current Research in EEPS Seminar: Paul Wessel, University of Hawaii
Hot-, Pole-, Plume- and Ridge-Spotting: Geometric Games of Plate Tectonics
The study of plate tectonics can be separated into the two broad categories “how?” and “why?”. Why plates move remains a fundamental research question and its answer is deeply connected to the Earth’s desire to lose heat, mantle rheology, the inferred current and modeled past patterns of mantle convection and the quest for answers ultimately goes back to the initiation of plate tectonics on Earth billions of years ago. How plates move is in contrast seemingly a much simpler question that largely revolves around plate kinematics and applications of spherical geometry.
Plate motions themselves are furthermore typically described in two ways: Relative plate motions describe the motion between two (or sometimes more) plates, usually with one of the plates being held fixed. In contrast, absolute plate motions attempt to describe the motion of a plate relative to a fixed mantle reference frame. Several such reference frames have been proposed and the most common, but also the most controversial, is the hotspot reference frame. Recent work suggests hotspots may not be as fixed as they once were believed to be, but evidence is also mounting that true polar wander has played a more important role in Earth’s history than previously recognized. In 2018, more than 50 years after Tuzo Wilson’s fundamental insight into plumes and absolute plate motion we are still hotly debating the origin of fundamental features such as the Hawaii-Emperor bend.
Ultimately, progress on understanding why plates and plumes move the way they do will likely be closely tied to constraints on absolute rather than relative plate motions, hence it is important to make progress on the quantification of absolute plate motions. In this talk I will review some of the ways plate motions are quantified and what we know about both relative and absolute plate motions, including the status of the infamous bend.