Here's why:

* Formation: Shale is a sedimentary rock, meaning it forms from the accumulation and compaction of sediments like clay, silt, and sand. These sediments are deposited on the Earth's surface, usually in water bodies like lakes or oceans.

* Pressure and Heat: Over time, the weight of additional sediments creates immense pressure, and the presence of water acts as a catalyst for chemical reactions. These processes compact the sediments, cement them together, and transform them into shale.

* Melting: The process of rock melting, called magma, happens deep within the Earth's mantle and crust due to extreme heat and pressure. This molten rock can rise to the surface and erupt as volcanoes, but it's not the origin of shale.

So, while shale is formed under pressure and heat, it doesn't involve the melting of rock material. It's a result of the gradual compaction and transformation of sediments over long periods.