Giant redwoods (Sequoiadendron giganteum) occur naturally only in groves on the western slopes of the Sierra Nevada Mountains of California. They are the world's largest trees by volume, growing to an average height of 50–85 meters and 6–8 metres in diameter. Record trees have been measured to be 94.8#160;metres high and over 17#160;m in diameter. The oldest known giant sequoia, based on ring count, is 3,500 years old.br/br/Sequoia bark provides significant fire protection, being fibrous, furrowed and up to 90#160;cm thick at the base of a large tree. At any given time, a large tree may be expected to have about 11,000 cones. The upper part of the crown of any mature giant sequoia invariably produces a greater abundance of cones than its lower portions. A mature giant sequoia has been estimated to disperse from 300,000-400,000 seeds per year. The winged seeds may be carried almost 200 metres from the parent tree.