Crand Canyon Tracks Were Not Formed During a Worldwide Flood

TB says: "1. The 2nd order sea-level curves were primarily generated tectonically
2. Specifically via sea-floor spreading and subduction processes which varied the volume of ocean basins."It appears to me that, as the bulges and subduction trenches occur only at the margins of oceanic tectonic plates, the changes in volume of ocean basins because of these factors would be a very small percentage change to the total ocean basin volume. And dramatic, widespread (simultaneous?) spreading and subduction events would be necessary to produce a noticeable change in ocean volume and consequential change in sea levels.Does TB envisage simultaneous movement of all of the tectonic plates comprising the Pacific Ocean basin to produce a noticeable change in sea level? Surely such a scenario would produce other detectable physical effects - for a start it seems like there would be a lot of heat and chemicals would be released as magma erupts to form the new sea floor.