Ignimbrite
“Welded from fiery volcanic clouds”
Ignimbrite is a volcanic rock formed when pyroclastic flows — superheated avalanches of gas, ash, and pumice — come to rest and weld together under their own intense heat. These deposits can cover thousands of square kilometers and reach hundreds of meters thick.
volcanic glass, pumice fragments, crystals of quartz, feldspar, biotite
Taupo Volcanic Zone (New Zealand), Yellowstone (USA), Central Andes, Bishop Tuff (California), Bandelier (New Mexico)
4-6 (varies with welding)
The Bandelier Tuff in New Mexico is an ignimbrite so soft that ancestral Pueblo people carved entire cliff dwellings into it, creating homes that are still standing a thousand years later.
Test Your Knowledge
What determines whether an ignimbrite is 'welded' or 'non-welded'?
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