THE EARTH

Focus-Science and Technology - - GEOLOGY -

CRUST 0-200KM DEEP

The sur­face of the Earth is made of rigid yet flex­i­ble tec­tonic plates. Con­ti­nen­tal plates are old and light, com­posed of low-den­sity min­er­als rich in sil­ica. Con­ti­nen­tal plates av­er­age 15 to 30 kilo­me­tres thick, although the most an­cient plates can be up to 200 kilo­me­tres thick. Oceanic plates are younger and denser, com­posed of high-den­sity min­er­als rich in iron and mag­ne­sium with lit­tle sil­ica. At just

7 to 10 kilo­me­tres thick, they are thin­ner than con­ti­nen­tal plates.

MAN­TLE 30-2,890KM DEEP

The thick­est layer of the Earth con­sists of hot, duc­tile rock rich in iron and mag­ne­sium. Over mil­lions of years, the man­tle flows in enor­mous con­vec­tion cells (shown here by yel­low ar­rows) that drive plate tec­ton­ics and feed hot spots be­low vol­ca­noes. Di­a­monds form in the up­per man­tle at depths of 150 to 800 kilo­me­tres.

CORE 2,890-6,371KM DEEP

The Earth’s iron-nickel core is a solid in­ner ball wrapped in a liq­uid outer core that is con­stantly in mo­tion. This hot, fluid me­tal gen­er­ates the planet’s pro­tec­tive mag­netic field, which de­flects the Sun’s harm­ful so­lar wind.

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