A scale is usually defined as the ratio between the distance between two particular places on the map and the actual distance between the two places on the actual ground surface.
It is widely used by the geographers while studying a map, in order to explain the relationship between the map distance and the earth's distance. This scale is mentioned in the map, mostly at the bottom of the map.
For example, a map scale of 1:500000, this means that 1 centimeter on the map is equivalent to 5000 meters = 5 kilometers on the ground surface.
By measuring the length of the volcanic chain and the time interval between the formation of the oldest structure and the youngest structure, an average speed of plate movement can be calculated.
