2. Volcanoes Get Ready for an ERUPTION!!!

3. What is a volcano? A weak spot in the crust where molten material, or magma, comes to the surface Magma- molten mixture of rock- forming substances, gases & water from the mantle Lava- Magma that reaches the surface

4. Where are volcanoes located? Volcanoes can be found: –Diverging Plate boundaries (mid-ocean ridge) –Converging plates with subduction zones Oceanic plate vs. oceanic plate Oceanic plate vs. continental plate –Hot spotsHot spots Area where magma from deep within the mantle melts through the crust like a blow torch –Example: Hawaiian IslandsHawaiian Islands

5. What is the Ring of Fire? A circular pattern located around the pacific ocean along the plate boundaries where volcanoes are more common

7. Results of Volcanoes Are constructive: –add new rock to existing land – form new islands Can be destructive –explosive eruptions changes the landscape of and around the volcano

8. Eruptions Why do volcanoes erupt? –Less dense magma seeps upward through cracks and creates volcanoes –Gas in the magma is trapped and builds pressure –Closer it gets to surface the less pressure it has and the gases separate (bubbles) –Gases dissolve on the surface and magma is carried out

9. Types of Eruptions determined by amount of silica (material made from the elements oxygen and silicon) 2 types: –Quiet Lava moves steadily and easily –Explosive Thick, sticky lava plugs vent like a cork and builds up pressure Explodes and releases pyroclastic flow –Volcanic ash: fine, rock particles –Cinders: pebble sized particles –Bombs: baseball to car sized particles

10. Types of Rocks Produced Type of lava produces different types of rocks –High silica lava: thicker, sticky, lighter colored Rhyolite Pumice obsidian –Low silica lava: flows readily, dark colored basalt

11. Stages of a Volcano Active: (live) erupting or has shown signs that it may erupt In the near future Dormant: (Sleeping) is not currently erupting but may/can erupt in the future Extinct: (dead) unlikely to erupt again

12. Other Volcanic Activity Hot springs –Groundwater is heated by near by magma rising to the surface and collects in natural pools

13. Other Volcanic Activity Geyser –Rising hot water and steam that gets trapped underground and builds pressure until it sprays to the surface

14. Land Formations from Lava & Ash Shield Volcano –Created by hot spots –Gently sloping Cinder Volcano –Steep –Cone-shaped hill/mountain Composite Volcano –Tall, cone-shaped mountain –Alternating layers of ash and lava

15. Land Formations from Lava & Ash Lava Plateaus –Lava moves far from the volcano before cooling which forms high plateaus Calderas –Huge hole left by the collapse of a volcanic mountain All magma has been emptied leaving a hollow shell that collapses

16. Land Formations from Magma Volcanic Neck: magma hardens in the volcanoes pipes and the soft rock wears awayVolcanic Neck: Dike: magma that was forced across rock layers hardens and the soft rock wears away Sill: magma that squeezed between rock layers hardens and the soft rock wears awaySill

17. Land Formations from Magma Batholith –Mass of rock formed when a large body of magma cools in the crust Dome Mountains –Rising magma is blocked by horizontal rock layers and forces the rock layers to bend upward into a dome shape and then the soft rock wears away