In this essay I will tell you about the main parts of a volcano and it's origin. The first main part I will tell you about is the magma chamber. A magma chamber is a large pool of molten rock, also called magma, sitting underneath the Earth's crust. The magma chamber can be more than three miles below the Earth's surface and the magma waits there for the pressure and gases to become too much to stay stable. The magma in the magma chamber is less tense than the mantle surrounding it, so it moves toward the surface of the Earth through cracks and flaws in the crust once a high enough pressure point is reached. Volcanic eruption is the result of magma reaching the Earth's surface. The second main part I will tell you about is the main vent. The main vent is the main channel through which the hot magma moves to reach the Earth's surface . To reach the Earth's surface, the main vent can be several miles long, having one end connected to the magma chamber and one reaching the surface. During volcanic eruption, most of the lava ejects through the main vent. The third main part I will tell you about is the secondary vent and cone. The larger volcanoes can have more than one vent for the magma to reach the Earth's surface. Secondary vents, with the main vent, are a way for the magma to move and reach the surface during volcanic eruption causing unforeseen dangerous situations when the lava flow suddenly widens or starts to flow to a different direction than previously predicted. Secondary cones form around secondary vents on large volcanoes. The forth and last main part I will tell you about is the crater. The crater is the circular formation with steep sides formed around the main vent where the lava, ash and rocks reach the surface of the Earth during the volcanic eruption. Most of the time the crater is formed to the top of the volcano, where the main vent ejects to the surface but, if the volcano has secondary vents, craters can also be found on the sides of the volcano. Crater lake is often formed to the summit crater when the crater fills with water. A divergent plate movement occurs when two plates move away from each other. Magma from the mantle underneath the crust rises up to the surface to cool and solidify at the plate boundary. This divergent boundary is considered constructive since new crust is formed. Divergent takes place at the boundary of the oceanic plates and forms new sea floor. This process is called sea-floor spreading. As magma rises up to the surface, it piles up and solidifies, slowly forming a long chain of mountains on the ocean floor, called an oceanic ridge. volcanoes can also form undersea at these divergent boundaries, they are called submarine volcanoes and have gentle eruptions. This is some information I've told you about the main parts of a volcano and it's origin.