Quirks & Quarks

How have supercontinents affected the Earth's rotation?

A listener asks whether the supercontinent Pangea caused the Earth to wobble in its rotation.

Did Pangea cause the world to wobble?

Supercontinents like this suggested formation 250 million years from now, do not impact the Earth's rotation (NASA)

This week's question comes to us from Jerome Cheung from Toronto. He asks: 

When the world only had one supercontinent, like Pangea, how did that affect the spin of the Earth with all the water on one side, and all the land on the other? 

Elaina Hyde, and assistant professor of physics and astronomy at York University reminds us that several supercontinents have formed throughout the Earth's history. These include Rodinia a billion years ago, Pannotia 600 hundred million years ago, and 335 million years ago Pangea. Within the next 250 million years, another will form as part of the continuous supercontinent cycle. 

The mass of land that makes up the continents, and the water in the oceans is just a fraction of Earth's mass. This means that supercontinents do not present much of a change as far as the effect on rotation for the whole planet. 

The Earth's rotation does wobble a bit, but it is not thought to be due to the distribution or concentration of land masses associated with supercontinents. Supercontinents may cause changes in climate and the pattern of storms, but it is the tidal forces generated by the Moon that have a much greater impact on the Earth's rotation.