Did the Ocean Used to Be Bigger?

Yes, research suggests the ocean used to hold more water on Earth's surface.

Recent scientific research indicates that early Earth likely had significantly more water on its surface compared to today. This fascinating discovery challenges previous assumptions about our planet's hydrological history.

According to a study published in the journal Philosophical Transactions of the Royal Society A, conducted by Korenaga and colleagues, Earth's surface initially held twice as much water as it does today. This finding suggests a very different picture of our planet's early state, potentially featuring larger or deeper oceans.

Why the Change in Water Amount?

The amount of water on Earth's surface isn't static over geological timescales. While we commonly think of the water cycle involving evaporation, precipitation, and runoff, there's a deeper, more fundamental cycle involving the Earth's crust and mantle.

As the researchers noted, "Like the oceanic plates themselves, water can cycle in and out of the magma beneath Earth's crust." This process is known as deep-water cycling.

• Water Going In: Water can be incorporated into minerals within oceanic plates as they subduct (sink) into the mantle.
• Water Coming Out: Water can be released from the mantle back to the surface through volcanic activity and outgassing.

The balance between water entering and leaving the mantle can shift over billions of years, leading to changes in the total amount of water available on the surface to form oceans. The study by Korenaga and colleagues suggests that in the early stages of Earth's history, the balance favored more water being present on the surface.

Comparing Past and Present Surface Water

This research provides valuable insight into the dynamic nature of Earth's water reservoirs and its geological evolution. It highlights that the familiar oceans we see today are just one phase in the planet's long history of water distribution.