Locations
Muskeg and quicksand have a few features in common. Both are soft, porous types of earth. Both of these natural land formations are found in areas where water in plentiful and drainage is poor. Muskeg is usually in northern climates and boreal forest biomes. Muskeg is an ecosystem within itself. Quicksand is found in warmer climates that contain deserts and sand, and unlike muskeg, it is considered dangerous.
Quicksand Composition
Quicksand is sand saturated with water and also has an upward current. The pressure of water and current keeps the grains of sand from having any friction, and the result is a fine, wet sand that can't support a lot of weight. Water comes in from the bottom of this gooey mess, so the top appears dry and the quicksand is hidden from view.
Muskeg Composition
Muskeg is a combination of many of the features you'll see in a northern forest, including ferns, swamps, ponds and bogs. Unlike quicksand, which refers to isolated patches of a certain kind of terrain, muskeg can stretch for many hundreds of miles and make up a whole landscape. The muskeg ecosystem is complex and varied, filled with plants and animals.
Dangers
The dangers of muskeg are more about transportation and infrastructure problems than immediate threats to life and limb. Many places in Canada remain isolated and uninhabited due to muskeg. Muskeg is almost impossible to build on or over, as it is either too soft or completely frozen over. Quicksand is not as dangerous as the movies portray. Quicksand is often only a few feet deep, and even if you do sink into it, the human body can float in quicksand just like water.