what did scientists believe about the earths crust before the theory of plate tectonics?

Before the theory of plate tectonics, scientists believed in a theory known as "Continental Drift" proposed by Alfred Wegener in 1912. According to this theory, all the continents were once joined together in a single landmass called Pangaea, which began to break apart about 200 million years ago. The continents then drifted to their current positions.

However, Wegener couldn't explain how the continents moved. His idea was not widely accepted during his time.

Before Wegener's theory, the prevailing belief was that the Earth's features were caused by vertical movements, a theory known as "geosynclinal theory". According to this theory, mountains were formed by the crust of the Earth wrinkling as it cooled.

It wasn't until the mid-20th century that enough evidence was gathered to support the theory of plate tectonics, which explained not only the movement of the continents but also the occurrence of earthquakes, volcanic activity, the creation of mountain ranges, and other geological phenomena.