Geography Quiz: Structure of the Earth and Rocks

Named after the Croatian seismologist who noticed that earthquake waves suddenly speed up at a certain depth, it marks the base of the crust and the top of the mantle, and is commonly shortened to the Moho.

They are transverse waves, in which particles vibrate at right angles to the direction of travel, and such motion cannot be sustained in a fluid, so S waves die out at the outer core.

Limestone is a sedimentary rock made largely of calcium carbonate, and when heat and pressure recrystallise it without melting it, the result is marble, the stone used in the Taj Mahal and in the Dilwara temples.

The Deccan Trap was formed by vast fissure eruptions in which lava spread over the surface and cooled quickly, giving a fine-grained extrusive igneous rock, basalt.

They are built up layer by layer as sediment settles over the remains of living things and hardens gently, so shells, bones and plant matter survive as fossils.

Almost half the weight of the crust, about 46.6 per cent, is oxygen, because it is locked into the silicate minerals of which nearly all crustal rocks are made rather than existing as free gas.

It marks the change from the molten outer core to the solid inner core, and is named after Inge Lehmann, who deduced from the behaviour of earthquake waves that the innermost part of the planet is solid.

Granite forms when magma cools slowly deep below the surface, which gives the crystals time to grow, so the rock is coarse and speckled.

The core bends P waves sharply and stops S waves altogether, so a belt of the Earth surface receives neither type of wave from a given earthquake.

It lies in the upper mantle just below the rigid outer shell, is weak and partly molten, and is the main source of the magma that reaches the surface through volcanoes; the plates slide over it.

Coal is a sedimentary rock formed from buried plant matter, and prolonged heat and pressure drive off its volatile content and rearrange the carbon, first into harder anthracite and finally into graphite, a metamorphic rock of nearly pure carbon.

Nife is formed from the chemical symbols of nickel and iron, the two metals believed to make up the central part of the planet, and the flow of that metal in the liquid outer core is what generates the Earth magnetic field.