7th Class Science Related to Competitive Exam Structure of the Earth

     Structure of the Earth

The internal and outer structure of the Earth is layered. Denser and heavier materials (iron and nickel) are present in the core. The layer between the inner core and mantle is outer core. The outer core of the Earth is in liquid form and is composed of iron and nickel.

Look at the following picture of the Inner layer of the Earth

The mantle layer of the earth is mainly composed of elements like, magnesium, iron, silicon and oxygen. Temperature of the mantle layer is about 3000°C Outer mantle of the Earth is thinner than the inner mantle. The upper layer (crust) is made up of rocks, which are again made up of amino silicates.

The outermost layer of the Earth is called crust. The average thickness of the continental crust is about 30 to 50/km and mostly contains granite. The average thickness of the oceanic crust is about 10 km and mostly contains basalt.

Continental crust is formed by the movement and colliding of the plates.

      The distance between the Sun and the Earth is slightly varied during the year. Which one of the following is the cause of the distance variation?

(a) The earth is tilted

(b) Rotation of the earth

(c) Rotation of the other planet

(d) All of these

(e) None of these

Answer: (a)

     Which one of the following is the most common cause of changing weather on the surface of the Earth?

(a) Distance between the earth and the moon

(b) Axial tilt                                        

(c) Rotation of the earth

(d) Static state of the sun

(e) None of these

Answer: (b)