Final answer:
A pyroclastic flow is a dense and fast-moving mix of hot lava blocks, pumice, ash, and volcanic gas that can destroy almost anything in its path, as seen in the eruption of Mount Vesuvius in 79 AD.
Step-by-step explanation:
A pyroclastic flow is a mixture of gas and dust emitted by a volcano that is so dense that it hugs the ground. Unlike lava flows, which are molten rock that emerges from a volcano and hardens into rock, or the volcanic ash, which consists of fragments of rock, minerals, and volcanic glass created during volcanic eruptions and measuring less than 2 mm in diameter, a pyroclastic flow contains a high-density mix of hot lava blocks, pumice, ash, and volcanic gas.
It is extremely dangerous because of its high speed and temperature, capable of destroying virtually anything in its path. This phenomenon was notably observed during the eruption of Mount Vesuvius in 79 AD, which devastated the ancient cities of Pompeii and Herculaneum.