Thundereggs specifically form in rhyolitic lava. Rhyolitic lava flows are volcanic flows composed of rhyolite — a high-silica (over 70% SiO2) volcanic rock. This type of lava is known for its ...

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 ...

The second type, rhyolitic magma, is thicker and has a higher resistance to flow. In Yellowstone ... with each one producing enough ash and lava to fill the Grand Canyon. However, the last ...