On a flight from North Carolina, US to Saint Croix, Virgin Islands, Jane Friedmann (Member 65,471) passed over the eastern edge of Puerto Rico. Cumulus clouds were building upwards over the island. They’d formed at the top of rising columns of air, known as thermals, lifting off the sun-warmed ground. Since these towers of cloud are taller, top to bottom, than the elevation of their bases from the ground, they’re the largest form of Cumulus clouds, known as Cumulus congestus. The jagged towers contrast with the calm, flat patches of the mid-level cloud Altocumulus over both the land and the sea beyond. ‘I contemplated the forces,’ says Jane, ‘that would cause such disparate neighbors to coexist.’