Buttress roots are large roots on all sides of a shallowly rooted tree. Typically, they are found in nutrient-poor rainforest soils and do not penetrate to deeper layers. They prevent the tree from falling over (hence the name buttress) while also gathering more nutrients. Buttresses are tension elements, being larger on the side away from the stress of asymmetrical canopies. The roots may interwind with buttress roots from other trees and create an intricate mesh, which may help support trees surrounding it. They can grow up to 30 feet (9.1 m) tall and spread for 30 metres above the soil then for another 30 metres below. When the roots spread horizontally, they are able to cover a wider area for collecting nutrients. They stay near the upper soil layer because all the main nutrients are found there.