How long from the worlds longest glaciers are from their widest tips. Maybe 5 miles, 10? Maybe even 20 miles long!? Well, be prepared to be shocked as I bring you the ten longest glaciers in the world and also where they are located… The Ten Longest Glaciers in the World and Where to Find Them 10 – Slessor Glacier, Glacier in the Antarctic – Last Recorded Length: 115 miles (185 km) The Slessor Glacier is a glacier is always flowing west into the Filchner Ice Shelf to the north of the Shackleton Range. First seen from the air and mapped by the Commonwealth Trans-Antarctic Expedition (CTAE) in 1956. Named by the CTAE for RAF Marshal Sir John