{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"26ae2890a14ea42651dfb910b3dc4d01fed855873d999ffd9cc1c6e56982e548","created":"2026-10-03T07:18:03Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"e554151436853789af7080d889cb7ee1b25dcde0b7421403b1af6d0a7f73409c","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"classification","assisted_by":[],"external_id":"earth.volcano-physics.fragmentation-criterion","kind":"well-posed","literature_status":"contested","n":"1","parents":[],"plain":"As magma rises, gas bubbles grow until the frothy melt may break apart into fragments and gas, turning a lava flow into an explosive jet. Scientists still disagree on which condition sets the break point.","posed_since":"","precise":"Determine the fragmentation criterion for vesiculating silicic magma: a critical porosity (about 0.6 to 0.8), a critical bubble overpressure relative to melt tensile strength, or a critical strain rate exceeding the inverse Maxwell relaxation time of the melt, including the effects of permeability and crystals. An answer is a single criterion, or a regime map, validated by shock-tube experiments and natural pyroclast textures.","problem_ref":null,"references":"","settled_by":"Decompression experiments spanning melt viscosity, porosity and permeability that collapse onto one fragmentation threshold, matched by textures of natural pumice.","status_note":"","title":"What criterion decides when rising magma shatters into ash?","topic_ref":"55338021c8ec86f4869f67772d325391efbf51e4cd18d86f6f0b30da4d45908b"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"680cc40f99f62c5ee111c7eb02d01031b41e2d72ffe48b62f9d535cbca1306dd","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"2dc17e8cb111a477275e4743777459ee6234a49228b4cfcd95870ea16e41c5f5","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"CIyzkoTIQX7nuxB1JQ4kYe99Z_-MOkkxtZUfdk3cNALvFvKl68sd5MUqJOi91vtjIPYfVKnapfltqDR729mbDw"},"schema":"pubphys.envelope/1"},"record_hash":"680cc40f99f62c5ee111c7eb02d01031b41e2d72ffe48b62f9d535cbca1306dd","leaf_index":1386}