A group of students measured pebble size at five sites along a shingle beach to investigate the impacts of longshore drift.
| Site | Distance from start of beach (m) | Mean pebble diameter (cm) |
|---|---|---|
| 1 | 0 | 12.4 |
| 2 | 100 | 9.8 |
| 3 | 200 | 14.1 |
| 4 | 300 | 7.1 |
| 5 | 400 | 5.3 |
Site 3 shows an anomalous result.
Suggest one possible explanation for this.
