mantlecirculating

Mantle circulation, or mantle convection, refers to the slow, large-scale movement of Earth's mantle driven by thermal buoyancy. Hot, buoyant material tends to rise while cooler, denser material sinks, transferring heat from the interior toward the surface over geologic timescales. Although the mantle is solid, its rocks flow on long timescales like a highly viscous fluid, enabling global rearrangement of material and heat.

The mantle extends from about 35 kilometers beneath the crust to nearly 2,900 kilometers below the surface and is commonly divided into the upper mantle, transition zone, and lower mantle. The asthenosphere, a relatively weak region within the upper mantle, acts as a lubricating layer that allows the overlying tectonic plates to move. Mantle circulation interacts with plate tectonics, as subducted slabs sink back into the mantle and may accompany upwellings that influence surface volcanism.

Mantle convection operates on tens to hundreds of millions of years, with viscosity, mineral phase changes, and composition shaping flow patterns. Subduction drives recycling of surface material into the mantle, while mantle plumes—localized upwellings—are proposed to contribute to hotspot volcanism and surface volcanism in some regions. The precise patterns of circulation—whether the mantle behaves as a single, whole-mmantle system or exhibits layered convection separating upper and lower mantle—are active areas of research.

Evidence for mantle circulation comes from seismic tomography showing temperature- and composition-related velocity anomalies, geochemical isotopic data from basalts, and the global pattern of plate motions. Numerical models and laboratory experiments simulate convection under varying viscosities and boundary conditions, helping to explain the coupling between mantle dynamics and surface geology. Mantle circulation is a foundational concept in understanding Earth’s geodynamics, shaping tectonics, volcanism, and thermal evolution.