Then, as now, the coast was made of unconsolidated sands and gravels from the fans of major rivers such as the Rakaia and Waimakariri. Powerful southerly waves in the Canterbury Bight rapidly eroded these weakly-resistant sands and gravels, and transported them northwards by longshore drift.
Then, as now, the coast was composed of unconsolidated sands and gravels from river fans like the Rakaia and Waimakariri. Strong southerly waves in the Canterbury Bight rapidly eroded these weakly-resistant sands and gravels, and transported them northward by longshore drift.