1. Get Ready for an ERUPTION!!!
Volcanoes
Get Ready for an
ERUPTION!!!

2. 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

3. 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 spots
Area where magma from deep within the mantle melts through the crust like a blow torch
Example: Hawaiian Islands

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

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

7. 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

8. 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

9. 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

10. 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

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

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

13. 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

14. 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

15. Land Formations from Magma
Volcanic Neck: magma hardens in the volcanoes pipes and the soft rock wears away
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 away

16. 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