Interior of the Earth Test - 3

The material in the upper mantle portion is called magma.

The innermost layer of the earth is the core. This central mass is mainly made of nickel and iron and therefore is known as NiFe.

Seismic Focus is the place where an earthquake originates and the focus is also called the hypocenter of an earthquake. The point on the surface of the earth where the seismic waves hit is known as the epicenter.

It is incorrect that the P-wave shadow zone is larger than the S-wave shadow zone. P-wave shadow zones are formed due to refraction, which causes the waves to deviate away. But S-wave shadow zones are created because these waves are completely blocked. Thus the S-wave shadow zones are much larger.

The most abundant metal in the earth crust is aluminium. Although aluminum is the most abundant metal in the earth's crust, it is never found free in nature. All of the earth's aluminum has combined with other elements to form compounds.

The portion of the interior beyond the crust is called the mantle. The mantle extends from Moho’s discontinuity to a depth of 2,900 km.

Volcanic eruption forms a source of obtaining direct information. As and when the molten material (magma) is thrown onto the surface of the earth, during volcanic eruption it becomes available for laboratory analysis. However, it is difficult to ascertain the depth of the source of such magma.

The Mohorovicic discontinuity, usually referred to as the Moho discontinuity, is the boundary between the Earth's crust and the mantle. It occurs at an average depth of about 8 kilometers beneath the ocean basins and 32 kilometers beneath continental surfaces.

The shadow zone results from S waves being stopped entirely by the liquid core. Three different S-wave phases show how the initial S wave is stopped (damped), or how it changes when encountering boundaries in the Earth.

The Deccan Traps from India, presently covering most of the Maharashtra plateau, are a much larger flood basalt province.