Question

What is the outermost layer of the Earth?

• A. Mantle
• B. Core
• C. Asthenosphere
• D. Crust

Answer 1

Answer:

D. Crust

Spheres of the earth

• Based on the analysis of the structure & composition generated during earthquakes, the Earth has been divided into different layers.

• Crust

• Mantle

• Outer core

• Inner core

Crust

• The comparatively thin outer shell of the earth.

• Approximately 10 km thick

• Two parts – Continental crust, oceanic crust.

• The continental crust is made of granitic, metamorphic, and sedimentary rocks. It's sometimes called sial because it's rich in aluminum silicates (Al-Si)

• Oceanic crust differs from continental crust in several ways: it is thinner, denser, younger, and of different chemical composition.

Mantle

• Located beneath the curst.

• Extended upto 2900km from the crust

• Two parts - upper mantle, lower mantle.

Upper mantle

• This layer is made up of solid and molten rock, and extends from the Earth's crust to a depth of 255 miles. It contains two parts: the asthenosphere, which is a transition zone of semi-molten rock, and the lithosphere, which contains the tectonic plates

Lower mantle

• This layer is located directly above the outer core, and is made up of solid rock that's around 7,000° F in temperature. It's hotter and denser than the upper mantle, and is less ductile. The intense pressure in the lower mantle keeps it solid, despite the high temperatures

Core

• Central part of the earth

• From 2900km to 6371 km

• Two parts - outer core, inner core

• Inner core - Solid, with a radius of 1,216 km. The inner core is under intense pressure, which keeps it solid despite its high temperature

• Outer core - Liquid, with a thickness of about 1,300 miles (2,092 km). The outer core is liquid because there isn't enough pressure to keep it solid.