The Changing Earth:The Changing Earth: Chapter 3 Mountains and Chapter 3 Mountains and

VolcanoesVolcanoes3.2 (Part 1) Volcanoes form as 3.2 (Part 1) Volcanoes form as

molten rock erupts.molten rock erupts.

VolcanoVolcano

• Opening in Earth’s crust through which molten rock, rock fragments, and hot gases erupt

Parts of a VolcanoParts of a Volcano

• Magma Chamber – Magma that rises towards Earth’s surface collects in a magma chamber, Magma remains here until it either cools and forms igneous rock or erupts

Parts of a VolcanoParts of a Volcano

• Main Vent – The point on the surface where magma leaves the volcano

• Side Vent – Magma is sometimes forced out through an opening on the side

• Crater – Bowl shaped area that forms around the volcanoes vent

Parts of a VolcanoParts of a Volcano

• Lava – Magma that has reached the surface

• Lava Flow – River of lava that pours down the side of the volcano

Parts of a VolcanoParts of a Volcano• Rock Fragments – A lot of the material

erupted from a volcano comes as rock fragments of different sizes

– Large fragments fall quickly but ash can be carried long distances by winds

Parts of a VolcanoParts of a Volcano

– Volcanic Ash (smallest – less than 2 mm in diameter) Ranges from the sizes of dust to the size of rice grains

Parts of a VolcanoParts of a Volcano

– Volcanic Cinders (Medium) Contain holes and tunnels left by escaping gases

Parts of a VolcanoParts of a Volcano

– Volcanic Bombs and Blocks (largest) Bombs are molten when they are thrown out and harden as they fly through the air, Blocks are solid pieces of rock and can be the size of houses

Parts of a VolcanoParts of a Volcano

• Volcanic Gases – Water Vapor and Carbon Dioxide, what looks like smoke rising from a volcano is actually ash and gases

• Pyroclastic Flows – dense cloud of superhot gases and rock fragments that races downhill, up to 800 °C and 160 KM/Hr– Most dangerous type of volcanic eruption