To determine which natural calamity cannot be predicted in advance very accurately, let's analyze each option:
1. Famine:
Famines are often predictable to some extent because they result from prolonged droughts, crop failures, or socio-economic factors. Early warning systems can monitor food security and weather patterns to anticipate famines.
2. Flood:
Floods can be predicted with reasonable accuracy using weather forecasting, rainfall data, and river level monitoring. Advanced systems provide warnings days or even weeks in advance.
3. Cyclone:
Cyclones (or hurricanes/typhoons) are tracked using satellite imagery and meteorological models. Their paths and intensities can be predicted several days in advance, allowing for timely evacuations.
4. Earthquake:
Earthquakes are currently the most difficult to predict accurately. While seismic activity can be monitored, there is no reliable method to predict the exact time, location, or magnitude of an earthquake in advance.
Final Answer:
The natural calamity that cannot be predicted in advance very accurately is Earthquake.