Subterranean Oceans
Subterranean oceans refer to vast reservoirs of water trapped within Earth’s interior, primarily within the mineral ringwoodite in the Transition Zone of the Upper Mantle. Recent seismological and geochemical evidence suggests these reservoirs may hold volumes comparable to or exceeding those of surface oceans, playing a critical role in the global water cycle, mantle convection, and plate tectonics.
Key Characteristics
- Location: Primarily located at depths of 410–660 km within the mantle transition zone, though water is also present in Olivine in the upper mantle and Bridgmanite in the lower mantle.
- Storage Mechanism: Water exists not as liquid pools, but as hydroxyl ions (OH-) bound within the crystal lattice of mantle minerals.
- Volume Estimates: Estimates vary significantly, ranging from 0.1 to several times the volume of the Hydrosphere, dependent on the heterogeneity of mantle domains.
- Role in Geodynamics:
- Facilitates lower-temperature Melting, aiding in Volcanism and Arc Volcanism.
- Influences mantle viscosity and convective patterns.
- Acts as a buffer for global climate over geological timescales via the Carbon Cycle.
Recent Discoveries & Context
- Seismic Imaging: Anomalous seismic wave velocities in the transition zone correlate with hydrated minerals, providing indirect evidence of large-scale water storage Unveiling Earth’s Geology: Hidden Oceans, Zealandia, and Mantle Provinces.
- Mantle Provinces: Distinct geochemical reservoirs within the mantle show varying degrees of hydration, suggesting that subduction zones transport surface water deep into the mantle over millions of years.
- Zealandia Connection: The geological complexity of Zealandia, a submerged continental mass, offers insights into how continental lithosphere interacts with mantle hydration processes during subduction and rifting.
Related Concepts
- Mantle Convection
- Subduction Zone
- Ringwoodite
- Earth’s Interior
- Hydrosphere