Most of the earthquakes we hear about are due to tectonic plates colliding or sliding past each other near plate boundaries. Yet researchers have detected some enigmatic earthquakes happening inside the more stable interiors of plates. Intermediate-depth earthquakes (IDEs), which occur around 70–3 00 kilometers (43–186 miles) below the surface, are especially puzzling because rocks at those depths are hot enough to flow more fluidly. ...read more read less