What caused the variations in pressure that created the convectional circulation pattern? Heating caused air contraction, which lowers its density and causes buoyancy -- and the air rises Heating caused air expansion, which increases its density and causes the air to sink Heating caused air expansion, which increases its density and buoyancy -- so the air sinks. Heating caused air expansion, which lowers its density and causes buoyancy -- so the air rises

The correct explanation for the variations in pressure that create convectional circulation patterns is: **Heating caused air expansion, which lowers its density and causes buoyancy -- so the air rises.** ### Explanation: 1. **Heating and Air Expansion**: When air is heated, it expands. This expansion means that the same mass of air occupies a larger volume. 2. **Density Changes**: As the air expands, its density decreases because density is defined as mass per unit volume. Therefore, warmer air is less dense than cooler air. 3. **Buoyancy Effect**: The lower density of the heated air makes it buoyant compared to the surrounding cooler air. This buoyancy causes the warm air to rise. 4. **Pressure Variations**: As the warm air rises, it creates a low-pressure area at the surface. Cooler air, which is denser, then moves in to replace the rising warm air, creating a circulation pattern. 5. **Convection Circulation**: This process of warm air rising and cool air sinking leads to convection currents, which are responsible for various weather patterns and atmospheric circulation. In summary, the correct statement highlights that heating causes air expansion, which lowers its density and leads to buoyancy, resulting in the rising of air.