The Equatorial Mountains, or Montes Aequinoctialis, are a massive range of mountains encircling Darwin IV's equator. It is only broken briefly by the Sinus Columbus, the great pass through the range. Darwin IV's montane region almost completely encircles the globe along the equator. While not impassable, the mountains present many problems for the planet's huge migratory herds. Storms and fogs claim thousands of individuals each year as they traverse the difficult and often icy mountain passes.