Does The asthenosphere consist of partially molten mantle rock?

The asthenosphere is commonly said to be made of partially molten rock, but that is not entirely true. There are areas of the asthenosphere that are partially molten, but they make up a small portion of its volume. The asthenosphere is hot enough that it would be molten is brought to the surface, but the enormous pressure inside Earth keeps it in a state that is technically solid. The rock is still rather soft though and can flow slowly over the course of thousands to millions of years. When you look at substances over such long periods of time the distinction between solid and liquid becomes a bit blurred.