What went wrong when the king rode under the arch?

It was too low and knocked off his crown

How does the chain of blame unfold in the poem?

Each accused person blames another, ending with the king's own changes

Name two direct sources of information about the earth's interior.

Surface and mined rocks (and deep drilling projects like the Kola well), and magma from volcanic eruptions.

What is the difference between focus and epicentre?

The focus is the point inside the earth where energy is released; the epicentre is the point on the surface directly above it.

How do P-waves and S-waves differ?

P-waves are faster and travel through solids, liquids and gases; S-waves are slower and travel only through solid materials.

Why do earthquake waves develop a shadow zone?

Because S-waves cannot pass through the liquid outer core, so a large zone beyond 105° from the epicentre receives no S-waves.

Which earthquake waves are the most destructive?

The surface waves, which cause displacement of rocks and collapse of structures.

How thick is the crust under oceans, continents and the Himalayas?

About 5 km under oceans, around 30 km under continents and up to 70 km in the Himalayan region.

What is the asthenosphere and why is it important?

The weak upper part of the mantle (extending to about 400 km) that is the main source of magma during volcanic eruptions.

What is the "nife" layer?

The core, made of heavy material mostly constituted by nickel (ni) and iron (fe), with a liquid outer core and a solid inner core.

Which type of volcanic eruption formed the Deccan Traps?

Flood basalt eruptions, which outpour highly fluid lava over thousands of square km.

Name three intrusive volcanic landforms.

Batholiths, laccoliths and dykes (also lapoliths, phacoliths and sills).

Interior of the Earth

Class 11 Geography · Fundamentals of Physical Geography · Chapter 3

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CBSE Class 11 · Geography

Earth's interior + plates: Unit II, 9 marks

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Summary

Because no one can reach the earth's centre, knowledge of its interior comes from direct sources (surface rocks, deep mines and drilling projects such as the Kola well at about 12 km, and volcanic magma) and indirect sources (temperature, pressure and density trends, meteors, gravitation, the magnetic field and especially seismic activity). An earthquake is the shaking of the earth caused by the sudden release of energy along a fault; the point of release is the focus (hypocentre) and the point on the surface above it is the epicentre. Earthquake waves are recorded on a seismograph and are of two kinds: body waves (P-waves, which are fast and travel through solids, liquids and gases, and S-waves, which travel only through solids) and surface waves, which are the most destructive. The fact that S-waves cannot pass through the liquid outer core creates a shadow zone and reveals the earth's layered structure. The earth consists of the crust (oceanic about 5 km, continental about 30 km, up to 70 km under the Himalayas), the mantle (with the weak asthenosphere as the source of magma), and the core (liquid outer core, solid inner core, the "nife" layer of nickel and iron). The chapter also classifies volcanoes — shield, composite, caldera, flood basalt provinces (like the Deccan Traps) and mid-ocean ridge volcanoes — and describes intrusive volcanic landforms such as batholiths, laccoliths, lapoliths, phacoliths, sills and dykes.

Interior of the Earth

Key terms

Focus (hypocentre)

the point within the earth where earthquake energy is first released.

Epicentre

the point on the surface directly above the focus, the first to experience the waves.

P-waves and S-waves

primary (fast, travel through all media) and secondary (slower, travel only through solids) body waves.

Shadow zone

the region where S-waves are not recorded, revealing the liquid outer core.

Asthenosphere

the weak upper-mantle zone that is the main source of magma.

Deccan Traps

a large flood-basalt province covering much of the Maharashtra plateau.

Extra questions & answers

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Which of these is a direct source of information about the earth's interior?

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Interior of the Earth

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Summary

Key terms

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Practice quiz · Interior of the Earth

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