A group of geography students investigated the hazards of a volcanic eruption by measuring the thickness of volcanic ash fall at different distances from the crater.
| Distance from volcanic crater (km) | Ash thickness (cm) |
|---|---|
| 2 | 45 |
| 5 | 38 |
| 10 | 12 |
| 15 | 28 |
| 20 | 8 |
| 25 | 3 |
Suggest one possible explanation for the anomaly shown in Table 1 at 15 km.
