Much of the areas in high latitudes, especially the Ismenius Lacus quadrangle, are suspected to still contain enormous amounts of water ice. Recent evidence has led many planetary scientists to conclude that water ice still exists as glaciers across much of the Martian mid- and high latitudes, protected from sublimation by thin coverings of insulating rock and/or dust. An example of this are the glacier-like features called lobate debris aprons in an area called Deuteronilus Mensae, which display widespread evidence of ice lying beneath a few meters of rock debris. Glaciers are associated with fretted terrain, and many volcanoes. Researchers have described glacial deposits on Hecates Tholus, Arsia Mons, Pavonis Mons, and Olympus Mons. Glaciers have also been reported in a number of larger Martian craters in the mid-latitudes and above. Glacier-like features on Mars are known variously as viscous flow features, Martian flow features, lobate debris aprons, or lineated valley fill, depending on the form of the feature, its location, the landforms it is associated with, and the author describing it. Many, but not all, small glaciers seem to be associated with gullies on the walls of craters and mantling material. The lineated deposits known as lineated valley fill are probably rock-covered glaciers that are found on the floors most channels within the fretted terrain found around Arabia Terra in the northern hemisphere. Their surfaces have ridged and grooved materials that deflect around obstacles. Lineated floor deposits may be related to lobate debris aprons, which have been proven to contain large amounts of ice by orbiting radar. For many years, researchers interpreted that features called 'lobate debris aprons' were glacial flows and it was thought that ice existed under a layer of insulating rocks. With new instrument readings, it has been confirmed that lobate debris aprons contain almost pure ice that is covered with a layer of rocks. Moving ice carries rock material, then drops it as the ice disappears. This typically happens at the snout or edges of the glacier. On Earth, such features would be called moraines, but on Mars they are typically known as "moraine-like ridges", "concentric ridges", or "arcuate ridges". Because ice tends to sublime rather than melt on Mars, and because Mars's low temperatures tend to make glaciers "cold based" (frozen down to their beds, and unable to slide), the remains of these glaciers and the ridges they leave do not appear the exactly same as normal glaciers on Earth.