Consider the following with respect to structure of the earth 1 n...........

Geography Earth Geology

Consider the following with respect to structure of the earth.

1. The oceanic crust is thinner than continental crust

2. Density of the Earth surface goes on decreasing from crust to core

3. Density of the mantle is more than that of outer core, as the inner core of the earth is in liquid state, while mantle is in solid state

Which of the statements given above is/are correct?

1 only

1 and 3 only

2 and 3 only

1, 2 and 3 only

छोटे Courses बड़े Results

Master Earth Geology

Prepare through Micro-courses

Try Now

Explanation:

Density of oceanic crust is greater than oceanic crust
Density of earth increases from crust to core
Though the second part of the statement (i.e as the inner core of the earth is in liquid state, while mantle is in solid state) is correct , but the density of outer core is more than that of the mantle

The Crust

It is the outermost solid part of the earth. It is brittle in nature. The thickness of the crust varies under the

oceanic and continental areas. Oceanic crust is thinner as compared to the continental crust. The mean thickness

of oceanic crust is 5 km whereas that of the continental is around 30 km. The continental crust is thicker in the areas of major mountain systems. It is as much as 70 km thick in the Himalayan region.

It is made up of heavier rocks having density of 3 g/cm3. This type of rock found in the oceanic crust is basalt. The mean density of material in oceanic crust is 2.7 g/cm3.

The Mantle

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. The upper portion of the mantle is called asthenosphere. The word astheno means weak. It is considered to be extending upto 400 km. It is the main source of magma that finds its way to the surface during volcanc eruptions. It has a density higher than the crust’s (3.4 g/cm3). The crust and the uppermost part of the mantle are called lithosphere. Its thickness ranges from 10-200 km. The lower mantle extends beyond the asthenosphere. It is in solid state.

The Core

As indicated earlier, the earthquake wave velocities helped in understanding the existence of the core of the earth.The coremantle boundary is located at the depth of 2,900 km. The outer core is in liquid state while the inner core is in solid state. The density of material at the mantle core boundary is around 5g/cm3 and at the centre of the earth at 6,300 km, the density value is around 13g/cm3. The core is made up of very heavy material mostly constituted by nickel and iron. It is sometimes referred to as the nife layer.