yläkuoreen

Yläkuoreen is the illative form of the Finnish noun yläkuori, which in geology refers to the upper portion of the Earth’s crust. In scientific usage, yläkuori denotes the shallow part of the crust lying above the crust–mantle boundary, commonly studied to understand crustal structure, tectonics, and surface processes. The exact depth of the boundary between the upper and lower crust varies by region and tectonic setting.

The upper crust differs in composition and rheology from the lower crust. In continental regions, it is typically dominated by felsic and sedimentary rocks such as granites and sedimentary rocks, often overlain by weathered and weatherable rocks. In oceanic regions, the upper crust is primarily basaltic. Below the upper crust lies the lower crust, which tends to be more mafic in character and mechanically distinct. The upper crust is where most weathering, crustal deformation, and early-stage magmatic and hydrothermal processes occur.

Geophysical and geological methods—such as seismic imaging, gravity studies, and rock sampling—are used to characterize yläkuori and to delineate its properties from the underlying mantle. Understanding the upper crust is important for interpreting tectonic history, resource distribution (minerals, groundwater), and crustal evolution, and the concept is also applied in planetary geology to describe analogous regions on other bodies.