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← 🌍 Earth science · usually met in Std 6-10

Inside the Earth

Crust, mantle, outer core and inner core — worked out almost entirely from the way earthquake waves travel, because nobody has ever been more than a few kilometres down.

crust — a few tens of km, thinner under the sea mantle — solid rock that creeps outer core — LIQUID iron and nickel its motion makes the magnetic field inner core — solid, hottest of all Nobody has drilled past the crust. All of this was worked out from how earthquake waves travel — and where they do not.
Drawn for Star Student.

The crust is thin — a few tens of kilometres under the continents, less under the oceans. Beneath it the mantle makes up most of the planet's volume: rock that is solid but creeps very slowly over geological time. The outer core is liquid iron and nickel, and its motion generates the Earth's magnetic field. The inner core is iron under such pressure that it stays solid despite being hotter still.

We know this because earthquake waves change speed and direction when they pass between materials, and some types cannot travel through liquid at all. Seismometers all over the world record what arrives and what does not, and the shadow that the liquid outer core casts is how its existence was discovered.

Worth knowing

  • The deepest hole ever drilled reached about 12 km, which does not even leave the crust.
  • The inner core is roughly as hot as the surface of the Sun.
  • The magnetic field deflects much of the solar wind, and life on the surface depends on it.

Want to see it moving? Search YouTube for “Inside the Earth” ↗ — we send you to the search rather than to one video, because a link to one video eventually rots.

See also

🌍 Plate tectonics🌍 Earthquakes⚛️ Magnetism

🧭 Do not take our word for it

This entry was written for Star Student in our own words — it is a summary, not a source. Here is where the people who actually hold these facts keep them. Go and check.

Your own textbook ↗Balbharati publishes the textbooks free to read online. Your chapter is the thing to check first — an encyclopedia is a summary, and the syllabus is the syllabus. Geological Survey of India ↗Rocks, earthquakes, the Himalaya and seismic zoning. India Meteorological Department ↗The monsoon, rainfall and cyclone warnings, from the department that issues them.

Last gone through: 1 October 2026 · How these entries are written

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