Jarðmöttlinum

Jarðmöttlinum is the Icelandic term for the Earth's mantle. It is the layer of silicate rock that lies between the Earth's crust and the outer core. The mantle is the largest part of the Earth by volume, making up about 84% of the Earth's total volume. It extends from the Mohorovičić discontinuity about 30 kilometers below the surface down to a depth of about 2,900 kilometers.

The mantle is primarily composed of silicate rocks rich in iron and magnesium. It is divided into two main regions: the upper mantle and the lower mantle. The upper mantle, extending from the crust down to about 410 kilometers, includes the lithospheric mantle (the rigid, outermost part of the mantle) and the asthenosphere (a hotter, weaker, and more ductile zone). The asthenosphere is crucial for plate tectonics as the lithospheric plates glide over it.

The lower mantle extends from 410 kilometers down to the core-mantle boundary. This region is hotter and denser than the upper mantle, and the rock is more rigid due to the increased pressure, although it still exhibits slow convective flow over geological timescales. This convection is the driving force behind plate movement and many geological phenomena like volcanism and earthquakes.

The temperature of the mantle increases with depth, ranging from about 500 to 900 degrees Celsius at the upper boundary to over 4,000 degrees Celsius at the lower boundary. While the mantle is mostly solid, the extreme heat and pressure allow it to behave plastically, flowing very slowly over millions of years. This slow churning of material in the mantle is a fundamental process shaping our planet.