Planet Earth : The different layers of our planet

graphic courtesy of the Fiji Mineral Resources Department

Those wanting to understand where earthquakes come from, should know a few basic principles  about our planet.

The Earth is made up of three concentric zones : the crust, mantle and core.

The crust is the thin outer layer forming the continents and the ocean floor.
Oceanic crust is thinner and more dense than continental crust. Some Ocean floors are only 15-20 km thick. The crust is enriched in O, Si, Al, Ca, Na and radioactive elements.

The mantle is the middle layer, rich in Mg, Fe and silicates (combinations of mainly silica and oxygen) and the core is the dense inner layer composed of iron and nickel. The inner part of the core is liquid and extremely hot.

The lithosphere is the solid part of the Earth, up to 120 km thick, composed of rocks and minerals, which in turn, compose the crust and part of the upper mantle.
Geologists study the lithosphere because it is the most easily accessible part of the Earth.

The most dangerous earthquakes for humans and infrastructure are shallow earthquakes (0-40 km’s depth).

(Some Text and Graphic courtesy of the Fiji Mineral Resource department)

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