The Geological mapping of Iceland’s Insular Shelf and Adjacent Deep Ocean.

We present our contribution to the European Marine Observation and Data Network (EMODnet) and the first comprehensive marine geological seafloor map compilation for Icelandic waters across an area of 764,000 km2. Our study is based on a variety of datasets, such as multi-beam and high-resolution bathymetry, sub-bottom profile and 2D seismic reflection, seafloor samples, and core data. This forms the basis for this map compilation, as well as previously published research. Mapping the seafloor geology of Icelandic waters is highly variable and challenging including volcanic, tectonic, sedimentary, and glacial features. These include e.g., present-day active and dormant volcanic systems, eruptive fissures and craters, seamounts and ridges, faults and lineaments, submarine lava borders, landslides, hydrothermal vents, terminal moraines, the extent of the last glacial maximum, glacial streamlines, drumlins, and gravity channels elements. Iceland´s onshore volcanic systems are well characterized based on their distribution of volcanic and tectonic fissures and rock compositions, which continue across the Icelandic insular shelf and the country´s marine domain. On the Icelandic insular shelf and shelf slopes, 17 active volcanic systems have been defined. Seamounts and Seamount ridges were mapped as isolated topographic features rising from the ocean floor that are typically volcanic and/or tectonic in origin. More than 600 craters and 250 eruptive fissures have been mapped and are common within active spreading zones or along extinct ridges. Subaerial and submarine lava flows, primarily seen as pillow lava sheets, have been mapped along the Reykjanes- and Kolbeinsey Ridges, craters, and eruptive fissures. Distinct submarine pillow lava flows can be seen deeper than 400 m depth with flow lengths up to 8-9 km from the crater of origin, and an aerial extent of 45-50 km2. Tectonic elements, fault zones, or fissures are prominent along the active spreading zones, and common across the insular shelf all around Iceland. They follow the primary structural grain of the mid-oceanic ridges north and southwest of Iceland and are predominantly active normal fault systems that are accompanied by earthquakes. Near the rift axes, these faults can form 20 km long and up to 400 m high continuous fault escarpments. Submarine landslides around Iceland are found in the fjords of east and west Iceland, but some are located on the insular slopes and on the Iceland-Faroe Ridge. The ages of these landslides are inferred to be of prehistoric age (>1200 years B.C.) as coastal areas became unstable after the last glaciation. Glacial landforms and erosional marks have been mapped along the entire insular shelf. This includes moraine ridges and glacial streamlines that hold information about past glacial movements and behaviour. This marine geological map compilation for Icelandic waters provides vital data input and starting point for future research and mapping projects that require maps such as seabed substrate, seafloor geology, coastal behaviour, geological events and probabilities, minerals, and submerged landscape map coverages.