hotspots almost all volcanoes occur at plate boundaries also known as plate margins however there are exceptions that can't be explained by plate movements these are found at places called hotspots the location of the major hotspots is shown on the map well-known examples are the Hawaiian islands and Yellowstone the nearest plate boundary to the Hawaiian islands is 3,200 km away so let's examine the processes that cause volcanoes here hotpots develop when the decay of radioactive elements in the Earth's core heats magma directly above it in the mantle the heated magma expands and becomes less dense than the surrounding magma so it rises to the surface in a mantle plume if there are lines of weakness in the crust the magma can break through and the lava erupts onto the surface if the hot spot is under the ocean the lava cools on contact with the water forming an underwater volcano over time the volcano builds up and can rise above sea level forming an island the hot spot is stationary so when the oceanic plate moves moves over it due to convection currents in the mantle a number of separate volcanoes are formed creating an island chain the volcanic islands that are furthest from The Hot Spot are the oldest while those closest to the hot spot are the youngest I.E the most recently formed the volcano above the hot spot is active whereas the older volcanoes no longer above the hot spot are extinct as magma is no longer supplied to older Islands they are weathered and eroded decreasing in size over time where hot spots occur under a continental plate magma erupts violently forming a Cera or large crater volcano as is the case in Yellowstone over time the cir is move away from the hot spot with the movement of the tectonic plate leaving a series of craters to summarize hot spots in the mantle explain the existence of volcanoes that are at a great distance from a plate boundary magma which is hotter than surrounding magma rises to the surface in a mantle plume cracks in the crust allow the magma to escape to the surface forming a volcano volano the hot spot is stationary therefore as the plate moves over it a new volcano is formed the volcanos can build to form an island chain if they are under the ocean keywords plate boundary an alternative term for a plate margin magma molten rock found in the mantle mantle plume an area of the mantle where magma is at a higher temperature than surrounding magma convection current currents in which a hot fluid Rises and a cooler fluid sinks