Volcanoes can be dormant (recent historical activity however now quiet), active (regular activity) or extinct (no activity in historical times and unlikely to erupt again).
About 30 kilometers under your feet present is the mantle of the Earth. It has very hot rock in liquid state. It is known as magma and extends down to the core.
Magma is lighter compared to rock surrounding it. This is why it goes up through cracks and weak points in the Earth's crust. When it erupts out of the surface, it delivers rock, lava ash and numerous volcanic gases along with.
The molten rock when under the Earth is known as magma while when it has erupted out, it is named lava.
Volcanoes are openings within the Earth's surface. Once they are active they can let gas, ash and warm magma escape in occasionally violent and spectacular eruptions.
Volcanoes are often located in which tectonic plates meet. This is especially correct for the Pacific Ring of Fire, a place around the Pacific Ocean in which over seventy five% of the volcanoes on Earth are located.
While many volcanoes form close to tectonic boundaries, they also can form in areas that include abnormally hot rock in the Earth. Called mantle plumes, these hotspots are located at a number of areas around the world with the most notable being in Hawaii.
Hot fluid rock beneath the Earth's surface is called magma, it is referred to as lava after it comes out of a volcano.
Some popular volcanic eruptions of contemporary times include Novarupta in 1912, Mount Krakatoa in 1883, Mt Pinatubo in 1991 and Mount St Helens in 1980.
Shield volcanoes are volcanoes with wide, gentle slopes and created by the eruption of liquid basalt lava (lava flows of low viscosity). Lawa moves out of volcano in every directions from a central summit vent or group of vents, creating a broad, gently sloping cone of flat, domical form, with a profile just like that a warrior's shield. The biggest volcanoes on Earth are shield volcanoes and one of the greatest known volcanoes in our solar system, Olympus Mons on Mars, is actually a shield volcano also.
Hawaiian shield volcanoes
The Hawaiian Islands are made up of linear chains of these volcanoes such as
Mauna Loa (largest active volcano on the planet)
Mount Kilauea (Big Island's youngest volcano)
Mauna Kea (tallest volcano on the island of Hawaii)Kohala Volcano (oldest)