Lava type
|
Must have
|
Commonly has
|
Commonly lacks
|
Must not have
|
|---|---|---|---|---|
| Pahoehoe subtypes:p-type pahoehoe,spongy pahoehoe | Smooth (continuous) flow top and base; glassy marginal selvage (0.2-1.5 cm thick); vesicular upper crust (15%-60% vesicles); lower vesicular crust (10%-50% vesicles) | 0.3- to 80-m flow thicknesses; inflation features (e.g., tumuli); thick massive interior (0%-5% vesicles); compound flow lobes; segregation structures (e.g., vesicle cylinders) | Angular and stretched vesicles | Autobrecciation |
| Pillow lava | Smooth (continuous) flow top and base; glassy marginal selvage (0.2-1.5 cm thick) | Concentric microvesicular zones; pipe vesicles; compound flow lobes; intercalated with hyaloclastite | Macroscopic vesicular zones | |
| Slab pahoehoe | Autobrecciated flow top; slabs of broken pahoehoe surfaces | A´a and pahoehoe clasts in breccia; thin basal breccia | ||
| Spiny pahoehoe | Continuous top and bottom spinose surface | High degree of crystallinity | Autobrecciation | |
| Rubbly pahoehoe | Autobrecciated flow top; broken and intact pahoehoe lobes; coherent vesicular crust below breccia; lower vesicular crust | Massive interior; distorted by rounded vesicles; smooth pahoehoe base | Well-defined vesicular zones | Basal breccia |
| A´a | Autobrecciated flow top; slabs of broken pahoehoe surfaces | 2- to 5-m flow thickness; clasts entrained within the core; core pushing into the flow-top breccia; 5%-20% vesicularity of clasts and core; minor eolian sediment infill | Round vesicles; inflation features; segregation structures | Smooth pahoehoe surfaces |
Note: Modified from Keszthelyi (2002).