Volcano 101. Classroom Antarctica — Classroom Antarctica. Volcanic Eruption by Ash Trees. What Is a Volcano? : Twig. Volcanoes are our most explosive landforms. Able to eject molten rock, and clouds of thick ash, high into the atmosphere... With devastating consequences. Volcanoes mostly occur along destructive and constructive plate boundaries, where plates are pushed together or dragged apart. Destructive or constructive boundaries Cracks or weaknesses allow magma to rise up from below the Earth's crust. Pressure builds up, which then releases suddenly, causing the magma to explode – a volcanic eruption. Magma that reaches the Earth's surface is called lava. Lava This molten lava eventually cools to form new rock. After more eruptions over time, the mound of rock builds up, forming a cone-shaped volcano. Volcanoes all have the same key structure... A collection of magma underneath the volcano forms a hot, bubbling furnace, called the magma chamber.
Magma Chamber The main vent allows this magma to escape. Main Vent And secondary vents... are smaller outlets the magma can travel through. Secondary Vents Crater.