Island Eddy consists of three low islets, inter-linked and flanked by extensive isthmuses and spits. The two isthmuses have shifted eastwards since the 1800s. Like many isthmuses, it is a location of great strategic value. This list of isthmuses is an appendix to the article "isthmus". All canals were open canals with no locks and were simply built across isthmuses. Both these isthmuses are very narrow compared to the bulk of the landmasses they unite. Others divided the continents by isthmuses, calling the continents "peninsulas".