Straits and Seaways: The importance of being connected

Straits and seaways connect basins between emerged landmasses, and they represent key areas for the regulation of water, sediment and biota exchanges, as well as local and global climate. However, their distinction is not always straightforward. Here, we challenge the community to compare the characteristics of straits and seaways, and to consider if they represent the same or different features. Different geomorphological, oceanographic, geological and depositional characteristics of straits and seaways based on well-documented modern and ancient case studies are presented. A first major difference is based on their spatial (e.g., widths in the order of kilometers for straits, and in the order of 100s to 1000s of kilometers for seaways) and temporal (from 10s kyrs to few Myrs for straits vs. several Myrs to 100s of Myrs for seaways) scale. Straits are characterized by convergence, turbulence and acceleration of water masses through one or multiple constrictions, so that currents flow parallel to the strait margins. Seaways are also characterized by water convergence due the geographical narrowing, but no significant water turbulence occurs, the influence of waves and storm waves is stronger compared to strait settings, and tidal currents can flow both parallel and perpendicular to the seaway margins. Straits can be regarded as individual depositional systems, whereas seaways are composed of a variety of depositional systems including the well-defined alluvial, deltaic, estuarine and deep-marine depositional systems (as well as straits). Straits and seaways represent end-members of a natural continuum during the evolution of a connection between two basins.