Science Olympiad Dynamic Planet Practice Test

Which layer of the Earth is known as the crust?

1. The thickest layer of the Earth

2. The thin outer layer made of various rock types

3. The layer primarily composed of liquid metal

4. The inner core made of solid iron and nickel

The correct answer is: The thin outer layer made of various rock types

The crust is indeed recognized as the thin outer layer of the Earth composed of various rock types. This layer is distinct from the other layers of the Earth, such as the mantle, outer core, and inner core, which have different characteristics and compositions. The crust is relatively thin compared to the underlying mantle, which is much thicker and made primarily of silicate rocks. It varies in thickness, averaging around 5 to 70 kilometers, but still remains the most superficial layer where life exists and where we live. The crust is divided into oceanic crust, which is denser and thinner, and continental crust, which is less dense and thicker, consisting of a variety of rock types including igneous, sedimentary, and metamorphic rocks. The other options describe different Earth layers. The thickest layer refers to the mantle, which is mainly solid rock but can flow very slowly. The option mentioning liquid metal corresponds to the outer core, which is primarily composed of molten iron and nickel. The inner core, made of solid iron and nickel, is very hot but remains solid due to immense pressure. Therefore, the characteristics outlined in the correct answer accurately reflect what the crust is composed of and its geological significance.