Final answer:
The outer shell of Earth is called the crust, which is a thin layer about 35 km thick on land and thinner under oceans. The crust and upper mantle form the lithosphere, which is around 100-200 km thick. Below the lithosphere is the mantle, followed by the liquid outer core and solid inner core.
Step-by-step explanation:
The outer shell of Earth is known as the crust, which is a cold, thin, brittle outer shell made of rock that is very thin compared to the radius of the planet. The crust comprises two types, continental and oceanic, varying in thickness, composition, and density.
The average thickness of the Earth's crust is about 35 kilometers on land and 5-6 kilometers under the oceans. Earth's crust and the uppermost part of the mantle together are referred to as the lithosphere, which is approximately 100-200 km thick and is the strong layer that includes the Earth's tectonic plates.
Beneath the crust lies the mantle, which extends down to a depth of about 2,900 kilometers. The mantle is more or less solid; however, under the high temperatures and pressures found there, mantle rock can slowly deform and flow.
Below the mantle, starting at a depth of 2,900 kilometers, is the core of the Earth, which is divided into two parts: a liquid outer core and a solid inner core. The core mainly consists of molten iron and nickel and is responsible for generating the Earth's magnetic field. The inner core is thought to be solid because of the immense pressure it is under, despite the high temperatures.