Pl help Scientists have established that some of the layers of Earth are solid, some are liquid, and some are semi-fluid. Explain how the scientists are able to determine the liquid and solid layers. Use at least two pieces of evidence to support your answer.

Several studies has been made in order to understand the layers of the earth. Some of the evidences that proved the existence of solid and liquid layers are as follows-

1. According to the concept of Isostacy, the earth's crust is a like a solid  wooden block, that floats over a vast liquid which is compared here with the mantle. Due to the variation in the crustal density, the crust sinks or gets uplifted.

2. From the geophysical point of view, the study of the seismic waves made clear that the earth is comprised of three distinct layers such as the crust, mantle and the core. Crust refers to to top layer, mantle is the middle part and core is the interior part of the earth which is divided into two types, inner core (solid in nature) and outer core (liquid in nature).