All that can be seen in this photograph is cloud stretching several hundreds of miles to the limb of the Earth, yet it tells us a great deal about the sea water in the Bering Sea below. The line or cloud margin running diagonally across the frame with dense thick cloud to the right and lighter, more broken cloud to the left reflects an ocean current margin. A difference in water temperature on either side of the margin is reflected in the cloud forms condensing above. This striking cloud boundary stretches for 500 to 600 miles in this photograph.