Tuff
Tuff is an igneous rock which forms by the eruption of a volcano where much volcanic material is blasted into the air and settles somewhere on the ground. If this material is cemented in situ it is called tuff.
The deposit of tuff can vary much. Close to the origin, most of the times a vent. The tuff layers are thickest and have a lens shape. More thick layers of tuff can be found in the direction of the blast or on the downwind side of the vent. Tuff deposits can reach up to hundreds meters of thickness made up of many cubic miles of eruptive volume.
Eruptive volume
The eruptive volume can be classified into three types:
- Volcanic gasses, made up of steam, carbon dioxide and a sulfur compound
- Lava
- Tephra, solid material which is ejected into the air during eruption
Tuff rings
A tuff ring is a small volcanic cone of low relief that surrounds a shallow crater. These craters, known as maars, are formed by explosions caused by hot magma coming in contact with cold groundwater. The explosion blasts fragments of bedrock, tephra, and ash from the crater. The tuff ring forms as these ejected materials fall back to Earth. Tuff rings range in size from several hundred meters across to several thousand meters. They are typically less than a few hundred meters in height and have a very gentle slope of less than ten degrees.
Welded tuff
Welded tuff is the name given for the soft and sticky particles that weld together upon impact or compaction due to the temperature of the particles. This happens mostly close to the vent because when particles travel they cool very rapid.
References
- https://geology.com/
- Schmidt, R. (1981). "Descriptive nomenclature and classification of pyroclastic deposits and fragments: recommendations of the IUGS Subcommission on the Systematics of Igneous Rocks". Geology. 9: 41–43. doi:10.1007/BF01822152. S2CID 128375559.
Tuff
| Type | Extrusive igneous rock |
|---|---|
| Clasts | Very coarse grained |
| Hardness | Hard |
| Color | Varying |
| Minerals | Can be every pyroclastic mineral |
| Touch | Rough |
| Image | Tuff |