It represents a cold front.
The Key, or Legend, or a map gives a list of the symbols used on the map and what they represent. There is a fairly standard set of symbols used for different types of map so that anyone looking at the map can understand what it is being shown. For example, on a weather map a cold front is shown as a black line with semi-circular bumps (in blue if coloured), a warm front is shown as a black line with triangles (in red if coloured) and an occluded front is shown as a black line with alternate semi-circular bumps and triangles.
The symbol for a Cold front on a weather map is represented with a blue line with blue triangles facing the direction that the front is traveling. A warm front is represented with a red line with red half-circles facing the direction of travel.
On a weather map, the symbol for a cold front is a blue line with blue triangles facing the direction that the front is moving.
An occluded front is represented by a pattern of blue triangles and red circles.
An occluded front is represented by a pattern of blue triangles and red circles.
For a cold front I believe there are blue triangles that are upside down in a line. For a Warm front I believe there are red triangles that are right side up on a line.
The type of front associated with purple triangles and semicircles on a weather map is a occluded front.
The map key gives one information about the symbols on a map.
Symbols on a map can typically be found in a legend or key, which provides explanations for various symbols used to represent features like roads, buildings, bodies of water, and other landmarks. This helps to interpret the information on the map accurately and understand what each symbol represents.
They stand for an approaching storm front. If I remember correctly, a red line means a warm front and a blue line means a cold front. The triangles show which direction the front is moving. Hope that helps.
symbols
Collectively, the symbols, with their meanings, on a map are called a 'legend'.