The higher the ratio of oxygen-18 to oxygen-16 in the shells of organisms that lived in the sea during the geologic past, the ____ the climate at that time.
A)colder
B)warmer
C)wetter
D)drier
E)more humid

Question

Quizplus · Accepted Answer

The ratio of oxygen-18 to oxygen-16 in the shells of marine organisms increases in colder climates because lighter oxygen-16 evaporates more readily, leaving behind water that is enriched in oxygen-18. This water is then incorporated into the shells of marine organisms, indicating a colder climate.

The Higher the Ratio of Oxygen-18 to Oxygen-16 in the Shells