Acommon misconception about earth's mantle is that it is a
thick layer of molten rock. explain, in your own words, why earth's
mantle is actually solid under normal conditions.

Lava or magma is considered to be in molten state while the earth's mantle is layer of rocks that changes its state

Explanation:

Earth's mantle is composed of solid rocks that exist in a liquid form, the upper layer is that of the Asthenosphere and the layer of the mantle is further divided into upper, lower and transitory layers.  Being the massive and most widely occurring layer covering the planet. It has a layer of silicate between the crust and outer core. It is approximately 1600 km thick.  The upper mantle contributes to the tectonic activity as the rocks in this layer are malleable. There are 15 major and minor slabs above the layer and lava i.e the molten rock is burned inside the magma at grater depths and as there exists water in the mantel the transition zone is evident from the upper and lower exchange of minerals.

Ithink it is space that makes up 70 percent