Final answer:
The Earth's mantle is primarily solid, made of rock that behaves in a plastic manner because the pressure is so high. However, there are areas of the mantle where melting occurs and the molten rock can erupt out of volcanoes.
Step-by-step explanation:
The Earth's mantle is primarily solid, composed of rock that behaves in a plastic manner in the long term. It consists of silicate minerals similar to those on the Earth's surface, but which have been altered under the intense pressure and heat in the mantle.
It might be surprising to hear that, considering we often associate the mantle with lava which we know is liquid. However, the majority of the mantle behaves as a solid because the pressure is so high that atoms are pushed together and the substance behaves as a solid despite the high temperatures.
There are areas of the mantle where melting occurs, such as at the boundary with the Earth's crust and in certain 'hot spots'. This molten rock can reach the surface through volcanic activity, which is why we often think of the mantle as being liquid.
Learn more about Earth's mantle