Volcanoes erupt when magma finds weaknesses within the earth’s surface. Pressure builds up and forces magma towards the surface. This pressure is released in the form of an eruption and the magma explodes to the surface. When magma reaches the surface it is called lava. Lava eventually cools down and forms rock.
There aren't any volcanoes along the East Coast but for over 20,000 years we have been affected by ash fall from volcanic activity. Remember if ash starts to fall, wear a dust mask or something to cover your face to protect yours lungs and breathing.
You can have a look at volcanic alerts in New Zealand at Geonet.