Lahars are a specific kind of mudflow made up of volcanic debris. They can form in a number of situations: when small slope collapses gather water on their way down a volcano, through rapid melting of snow and ice during an eruption, from heavy rainfall on loose volcanic debris, when a volcano erupts through a crater lake, or when a crater lake drains because of overflow or wall collapse.
A relay is an electromagnetic switch operated by a relatively small electric current that can turn on or off a much larger electric current. The heart of a relay is an electromagnet (a coil of wire that becomes a temporary magnet when electricity flows through it).
Automotive Relays and How They Work. Automotive relays of all shapes and sizes can be found in just about every car, truck, and even boats. Relays in general are used to enable a low amperage circuit to switch on or off a higher amperage circuit, like turning on your headlights.f you were to try and directly hook up your headlights to the headlight switch you would exceed the amperage rating of the switch, melt wires, and risk an electrical fire. Relays are also used to switch multiple things at the same time using one output.