Bouldering is a form of rock climbing that is performed on small rock formations or artificial rock walls, known as boulders, without the use of ropes or harnesses. While it can be done without any equipment, most climbers use climbing shoes to help secure footholds, chalk to keep their hands dry and provide a firmer grip, and bouldering mats to prevent injuries from falls. Unlike free solo climbing, which is also performed without ropes, bouldering problems (the sequence of moves that a climber performs to complete the climb) are usually less than 6 meters (20 ft.) tall. Traverses, which are a form of boulder problem, require the climber to climb horizontally from one end to another.:3Artificial climbing walls allow boulderers to train indoors in areas without natural boulders. In addition, Bouldering competitions take place in both indoor and outdoor settings.
The sport originally was a method of training for roped climbs and mountaineering, so climbers could practice specific moves at a safe distance from the ground. Additionally, the sport served to build stamina and increase finger strength. Throughout the 20th century, bouldering evolved into a separate discipline. Individual problems are assigned ratings based on difficulty. Although there have been various rating systems used throughout the history of bouldering, modern problems usually use either the V-scale or the Fontainebleau scale.
The growing popularity of bouldering has caused several environmental concerns, including soil erosion and trampled vegetation, as climbers hike off-trail to reach bouldering sites. This has caused some landowners to restrict access or prohibit bouldering altogether.
The characteristics of boulder problems depend largely on the type of rock being climbed. For example, granite often features long cracks and slabs while sandstone rocks are known for their steep overhangs and frequent horizontal breaks. Limestone and volcanic rock are also used for bouldering.:21–22
There are many prominent bouldering areas throughout the United States, including Hueco Tanks in Texas, Mount Evans in Colorado, and The Buttermilks in Bishop, California. Squamish, British Columbia is one of the most popular bouldering areas in Canada.:80–81 Europe also hosts a number of bouldering sites, such as Fontainebleau in France, Albarracín in Spain, and various mountains throughout Switzerland. Africa's most prominent bouldering areas are the more established Rocklands in South Africa and the new kid on the block Oukaimeden in Morocco or recently opened areas like Chimanimani in Zimbabwe.