Driftwood is wood that has been washed onto a shore or beach of a sea, lake, or river by the action of winds, tides or waves. It is a form of marine debris or tidewrack. Driftwood is wood that has been washed onto a shore or beach of a sea, lake, or river by the action of winds, tides or waves. It is a form of marine debris or tidewrack. In some waterfront areas, driftwood is a major nuisance. However, the driftwood provides shelter and food for birds, fish and other aquatic species as it floats in the ocean. Gribbles, shipworms and bacteria decompose the wood and gradually turn it into nutrients that are reintroduced to the food web. Sometimes, the partially decomposed wood washes ashore, where it also shelters birds, plants, and other species. Driftwood can become the foundation for sand dunes. Most driftwood is the remains of trees, in whole or part, that have been washed into the ocean, due to flooding, high winds, or other natural occurrences, or as the result of logging. There is also a subset of driftwood known as drift lumber. Drift lumber includes the remains of man-made wooden objects, such as buildings and their contents washed into the sea during storms, wooden objects discarded into the water from shore, dropped dunnage or lost cargo from ships (jetsam), and the remains of shipwrecked wooden ships and boats (flotsam). Erosion and wave action may make it difficult or impossible to determine the origin of a particular piece of driftwood. Driftwood can be used as part of decorative furniture or other art forms, and is a popular element in the scenery of fish tanks. The EPA includes driftwood in its list of 'Items You Should Never Burn in Your Appliance,' because it will 'release toxic chemicals when burned'. According to Norse mythology, the first humans, Ask and Embla, were formed out of two pieces of driftwood, an ash and an elm, by the god Odin and his brothers, Vili and Vé. The Vikings would cast wood into the sea before making landfall. And the location of the wood would be an indication as to where to build their mead halls. The wood used would found the high-seat pillars of the new hall. Driftwood carried by Arctic rivers was the main, or sometimes only, source of wood for some Inuit and other Arctic populations living north of the tree line until they came into regular contact with European traders. Traditional Inuit boats such as the kayak were fashioned from driftwood frames covered in skins. The Inuit classified driftwood in to 7 different types, each possessing its own unique material and visual properties. Driftwood could be used to make bows if it was straight grained and in reasonably good condition; these were reinforced with sinew cables. The Inuit even made arrows from driftwood; these were often short and fitted with bone or antler foreshafts. Dry scrapings produced by working this material were collected, stored and used for the starting of fires year-round by Inuit peoples. Wood that is burned today in these regions mainly consists of the remains of condemned wooden structures. Driftwood is still used as kindling by some. Woods with resinous qualities, such as cedar, are preferred for their lengthier burning times.