10.3 TYPES OF VOLCANOES 1. Plate tectonics accounts for important features of Earth’s surface and major geologic events. As a basis for understanding this concept: d. Students know that earthquakes are sudden motions along breaks in the crust called faults and that volcanoes and fissures are locations where magma reaches the surface. e. Students know major geologic events, such as earthquakes, volcanic eruptions, and mountain building, result from plate motions.

WHY ARE VOLCANOES DIFFERENT?  Different volcano shapes and volcano eruptions are caused by different magma.

HOW CAN WE COMPARE MAGMA?  1. The amount of SILICA  Silica is a material that makes things viscous (gooey)  Small amounts make lava runny  Large amounts make lava thick and sticky  2. The amount of DISSOLVED GAS  Small amounts make magma flat, quiet eruption  Large amounts make lava bubbly, explosive eruption  (Just like soda!)

WHAT KIND OF VOLCANOES HAVE LOW LEVELS OF SILICA?  Low levels of Silica and low levels of dissolved gas produces SHIELD VOLCANOES. These are wider and flatter. There are no explosive eruptions.  Low levels of Silica and high levels of dissolved gas produces CINDERCONES. The gas in the magma creates FIRE FOUNTAINS!

WHAT KIND OF VOLCANOES HAVE HIGH LEVELS OF SILICA?  Composite volcanoes are tall and cone-shaped.  Also known as a Stratovolcano  Low gas = oozing out like toothpaste, obsidian created  High gas = pressure builds and builds and then BOOM!, pumice and ash created

WHAT HAPPENS WITH EXPLOSIVE ERUPTIONS?  PYROCLASTIC FLOW – a cloud of volcanic material that races down the side of the volcano with high SPEED, FORCE and HEAT.  LAVA BOMBS – blobs of molten material that gets thrown in an eruption  LAHARS – Mudflows that occur if there is water present during an eruption.

HOW ARE VOLCANOES PART OF THE WATER CYCLE?  Water from the ocean gets pulled down during subduction  Water is evaporated during an eruption  Water condenses back into the ocean

EXIT TICKET COPY THESE QUESTIONS AND ANSWER IN YOUR SCIENCE NOTEBOOK. 1. What two ingredients in magma affect the type of explosion and shape of a volcano? 2. What type of volcano has no explosive eruptions? 3. What are the three types of volcanoes? Describe how they are different.

HOMEWORK  Bring your materials to work on your volcano tomorrow.