Changes in global temperature over the last 1.8 million years have been calculated by measuring
A)the thickness of glacial deposits.
B)the amount of carbon-14 in volcanic ash layers.
C)the stable oxygen isotopes in shelly fossils.
D)the amount of carbon dioxide in shelly fossils.

Question

Quizplus · Accepted Answer

The stable oxygen isotopes in shelly fossils are used to calculate changes in global temperature over the last 1.8 million years. This method relies on the principle that the ratio of oxygen isotopes in the shells of marine organisms varies with the temperature of the seawater in which they lived, providing a record of past temperatures.

Changes in Global Temperature Over the Last 1