#pyroclastic flow

So I'm adding dwarves to my setting but not your typical short stubby fleshy dudes. But rather short stubby rocky dudes. There are three types of dwarves upper crust, mid crust, and lower crust. They grow at different levels in the earth's crust and are made out of different rocks depending on what's available at that level. Like if they're closer to the surface they're made out of rocks and gems and such that naturally grow at that level.

Small issue though I have no idea what grows- forms? At those different levels farther or closer to the surface and I also don't know in what amounts. What's rare and what's common? I imagine diamonds don't grow in the same place as amethyst.

If you guys could help me out it would be much appreciated!

P.s. I did try googling it first but I couldn't find anything.

P.p.s. a visual representation like a rock map or something would be nice but is not required.

A superheated avalanche ( >800 °C / >1,500 °F) of toxic gases, volcanic ash, pumice, shattered rock and blocks of lava over 320kph (200mph).

It's the deadliest weapon in a volcano's arsenal.

And this is what the monster SOUNDS like:

This is what an erupting volcano looks like from space.

📽: NASA Johnson

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A fortuitous orbit of the International Space Station allowed the astronauts this striking view of Sarychev Volcano (Kuril Islands, northeast from Hokkaido in Japan to Kamchatka Peninsula in Russia) in an early stage of eruption on 12 June 2009.

Sarychev Peak is one of the most active volcanoes in the Kuril Island chain, and it is located on the northwestern end of Matua Island.

Prior to June 12, the last explosive eruption occurred in 1989, with eruptions in 1986, 1976, 1954, and 1946 also producing lava flows.

Ash from the multi-day eruption has been detected 2,407 kilometers east-southeast and 926 kilometers west-northwest of the volcano.

Commercial airline flights are being diverted away from the region to minimize the danger of engine failures from ash intake.

This detailed astronaut photograph is exciting to volcanologists because it captures several phenomena that occur during the earliest stages of an explosive volcanic eruption.

The main column is one of a series of plumes that rose above Matua Island on June 12.

The plume appears to be a combination of brown ash and white steam. The vigorously rising plume gives the steam a bubble-like appearance.

In contrast, the smooth white cloud on top may be water condensation that resulted from rapid rising and cooling of the air mass above the ash column.

This cloud, which meteorologists call a pileus cloud, is probably a transient feature: the eruption plume is starting to punch through.

The structure also indicates that little to no shearing wind was present at the time to disrupt the plume.

(Satellite images acquired 2-3 days after the start of activity illustrate the effect of shearing winds on the spread of the ash plumes across the Pacific Ocean.)

By contrast, a cloud of denser, gray ash — probably a pyroclastic flow — appears to be hugging the ground, descending from the volcano summit.

The rising eruption plume casts a shadow to the northwest of the island.

Brown ash at a lower altitude of the atmosphere spreads out above the ground at image lower left.

Low-level stratus clouds approach Matua Island from the east, wrapping around the lower slopes of the volcano.

Only about 1.5 kilometers of the coastline of Matua Island are visible beneath the clouds and ash.