VOLCORE, a global database of visible tephra layers sampled by ocean drilling (NERC Grant NE/P020895/1)

Tephra layers are recorded in the Visual Core Description (VCD) during systematic logging of sediment cores on board during an expedition. Every expedition produces reports which include the visual core description forms (VCDs), these were the primary source used for VOLCORE data collection. Visual core description forms for all OD expeditions were individually inspected for recording of tephra, ash, glass or other volcanic products. To be consistent across all of the expeditions only the shipboard VCDs were used as the data source, published post-cruise literature were not used. If the user is interested in a particular expedition, they should check the literature for post-expedition updates regarding tephra identification. VOLCORE provides a global overview of volcanism via a standardised data capture method, it does not include post-expedition studies. The data were collected from 3,886 drill holes (expeditions 1–381), distributed across all major seas and oceans. For each tephra layer that passed the criteria (>25% tephra content) we extracted data on core location, on depth down the core and tephra layer thickness. Definitions of a ‘tephra layer’ vary between expeditions, so care should be taken when using VOLCORE, it is highly advisable to carefully read the accompanying data descriptor paper (https://www.nature.com/articles/s41597-020-00673-1). The data are spread over five worksheets, one with details per tephra layer (or patch), one with details for each drill hole, one with the age-depth models used in this study, one with the coring information for each drill hole. A fifth sheet titled ‘Key’ describes the basic meaning of every column in the data worksheets. The individual data sheets can be linked via the common Hole and Site ID fields (HID, SID). We estimated the age of the layer using age-depth models for each drill hole. In each age-depth model the rate of deposition between tie points in the age-depth model is assumed to be linear. The listing of a tephra layer in VOLCORE is based on descriptive criteria and does not imply any firm knowledge of source processes, i.e. primary fall, flow or reworking.

INSPIRE Implementing rules laying down technical arrangements for the interoperability and harmonisation of Geology

Commission Regulation (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services