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what are the sub layers of the mantle
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If you mean Earth's mantle, it’s commonly divided into these sublayers (depths are approximate):
- Upper mantle
- Lithospheric mantle: the rigid uppermost part that, together with the crust, forms the tectonic lithosphere (extends from the Moho down to roughly 50–200 km depending on location).
- Asthenosphere: a weaker, partially ductile layer beneath the lithosphere that can flow on geological timescales and allows plate motion (roughly from the base of the lithosphere down to ~410 km; thickness varies).
- Transition zone
- Between about 410 km and 660 km depth. Characterized by major phase changes of olivine (to wadsleyite/ringwoodite then to bridgmanite + ferropericlase) that produce seismic discontinuities at ~410 km and ~660 km.
- Lower mantle (sometimes called the mesosphere)
- From ~660 km down to the core–mantle boundary at ~2891 km. Higher pressures and temperatures, dominated by high‑pressure silicate minerals; convects on long timescales.
- D″ (D double-prime) layer
- The lowermost ~200–300 km of the mantle just above the core–mantle boundary. It shows complex seismic structure (including ultra‑low velocity zones) and likely chemical/phase heterogeneity.
Brief notes: the mantle is mostly solid silicate rock but behaves viscously over long timescales and convects; the 410 km and 660 km boundaries are the most prominent seismic markers that define the transition zone.
- Upper mantle
- Lithospheric mantle: the rigid uppermost part that, together with the crust, forms the tectonic lithosphere (extends from the Moho down to roughly 50–200 km depending on location).
- Asthenosphere: a weaker, partially ductile layer beneath the lithosphere that can flow on geological timescales and allows plate motion (roughly from the base of the lithosphere down to ~410 km; thickness varies).
- Transition zone
- Between about 410 km and 660 km depth. Characterized by major phase changes of olivine (to wadsleyite/ringwoodite then to bridgmanite + ferropericlase) that produce seismic discontinuities at ~410 km and ~660 km.
- Lower mantle (sometimes called the mesosphere)
- From ~660 km down to the core–mantle boundary at ~2891 km. Higher pressures and temperatures, dominated by high‑pressure silicate minerals; convects on long timescales.
- D″ (D double-prime) layer
- The lowermost ~200–300 km of the mantle just above the core–mantle boundary. It shows complex seismic structure (including ultra‑low velocity zones) and likely chemical/phase heterogeneity.
Brief notes: the mantle is mostly solid silicate rock but behaves viscously over long timescales and convects; the 410 km and 660 km boundaries are the most prominent seismic markers that define the transition zone.
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