What did the drowned forests in cascadia show scientists about the size of past earthquakes in the region?

The drowned forests in Cascadia provided crucial evidence about the magnitude of past earthquakes through the study of tree rings and sediment layers. When massive subduction zone earthquakes occur, they can cause land subsidence, leading to the inundation of coastal forests. By dating the layers of sediment and the growth patterns of the trees, scientists have been able to reconstruct a timeline of significant seismic events, revealing that some past earthquakes reached magnitudes of 9.0 or greater. This research underscores the potential for future large-scale earthquakes in the region.