category of mid-ocean ridges, accounting for about 15% of the total length of mid-ocean ridges worldwide. Since ultraslow ridges are located in the Arctic Ocean and the stormy Southwest Indian Ocean and are therefore [...] Ultraslow spreading mid-ocean ridges At mid-ocean ridges, the lithospheric plates move apart at rates of about 5-150 mm/year and new oceanic lithosphere is continuously formed. At low spreading rates of [...] making its way to the ocean floor through a cold, thick lithosphere. Therefore, the formation process of new ocean lithosphere differs at ultraslow spreading ridges from all other ocean basins. Ultraslow ridges