What is a Volcano Volcanoes begin deep within the Earth Hot molten rock called magma collects far underground Forces below it crack the underground rock Pressure pushes melted rock upward through these openings The molten rock explodes from the opening or flows out The molten rock is now lava Once cooled the lava solidifies and becomes igneous rock Over time a cone shape builds up Hot Fact Igneous rock is one of three main types of rocks The other types are sedimentary and metamorphic 4
ash and gas cloud rock fragments lava crater cone vent magma chamber Magma chambers underground hold different amounts of magma Cracks and vents allow the hot magma to move Did You Know The word volcano came from the name of the Roman god Vulcan People once thought the lava and gas clouds erupting from the island of Vulcano was Vulcan forging thunderbolts for Jupiter king of their gods and for Mars their god of war upward and collect in chambers in volcanoes Certain conditions force the magma above ground where it cools as lava 5
Mt Kilimanjaro in Tanzania is a dormant volcano It is the tallest mountain in Africa and is 19,341 feet 5,895 meters tall Volcanoes that have produced lava or eruptions in the past 10,000 years or since the Ice Age are active volcanoes Eruptions happen when molten rock gases and ash from below the Earth’s surface are forced up and out through cracks Hot Fact Alaska contains three-fourths of the volcanoes that have erupted in the past 200 years 6 Dormant volcanoes are active volcanoes that are not erupting but are expected to erupt again Extinct volcanoes have not erupted in at least 10,000 years and are not expected to erupt again Still some extinct volcanoes have surprised people and erupted in the past
Types of Volcanoes Volcanoes are often classified by shape and how they were formed However not every kind of eruption falls into a single group The speed of the flowing lava builds the shape Slow-moving lava forms a gently sloping cone called shield volcanoes They are not normally explosive Shield volcanoes are most often basalt a type of lava that is very liquid and flows easily This view of Mauna Loa from Mauna Kea in the late evening shows the distinctive shape of shield volcanoes Mauna Loa one of five volcanoes that form the island of Hawaii is one of the largest active volcanoes today The mountain it forms is 60 miles 97 kilometers long and 30 miles 48 kilometers wide Mauna Loa is the Hawaiian term for long mountain It is a shield volcano Its eruptions have averaged one every six years for the past 300 years 7
