Volcaniclastic sediments from mid-oceanic Kolbeinsey Ridge, north of Iceland: evidence for submarine volcanic fragmentation processes

Volcaniclastic sediments of the active Kolbeinsey Ridge reflect changing fragmentation mechanisms due to increasing sea level during the last deglaciation. Glass shards deposited on the western flank of the mid-oceanic ridge before 13.4 ka are vesicular (20%-60%), whereas shards deposited since 13.4 ka are mostly vesicle free and of hyaloclastic origin. An eruption mechanism is proposed in which hot vesiculating bombs from a low-energy eruption are transported upward through the water column by convection. These particles reach their volcanic fragmentation depth (VFD) and undergo secondary fragmentation, creating the vesicle-rich shards recovered near the ridge. Rising sea level since the end of the last glaciation was sufficient to prevent the erupted particles from reaching the VFD, thus ending the formation of vesicle-rich shards. -from Authors