Fallen trees are simply trees that have been somehow knocked over. While a single fallen tree may block a forest path or act as a perilous bridge over a canyon or river, a large area or a trail of fallen trees may be the result of a violent wind, a crash landing, a meteor impact, or the movement of a massive behemoth. Fallen trees may be hollow logs and may have extensive roots now upended. There may be a hole where they once stood that may connect to a cave. Fallen trees may act as terrain hazards or obstacles.