Effect of sea level on tectonic plates. Illustration showing a subduction zone between two tectonic plates. An oceanic plate (right) is descending beneath a continental plate (left). Subductions zones have a high rate of volcanic and earthquake activity. If there is an increase in pressure on the subduction zone, for example caused by a rise in sea level above it, the subduction process is accelerated and volcanic and earthquake activity can become more frequent and more violent.