Lava domes are rounded, steep-sided mounds built by magma that is highly resistant to flow, usually either dacite or rhyolite. Such magmas are typically too viscous to move far from the vent ...

That’s hotter than the surface of the planet Venus, and hot enough to melt many rocks. It’s also as hot ... like the thicker dacite lava that erupts at Mount St. Helens in Washington state.