1. Volcanoes

2. Volcanoes Forms new land and ocean floor
Replenishes the atmosphere with gases and water vapor
Destructive to society

3. Types of volcanic Eruptions
Non-Explosive Eruptions
Explosive Eruptions

4. Non-Explosive Volcanic Eruptions
are the most common
found on land and ocean floors
can release huge amounts of lava, gases and mud
Most of the ocean floor and Hawaiian Islands are from non-explosive eruptions

5. Explosive Eruptions Are much rarer than Non-explosive eruptions
Can be very destructive
Clouds of hot debris, gases and ash are rapidly ejected from the volcano

6. Volcanic features

7. Types of Lava Aa
Pahoehoe
Pillow Lava
Blocky Lava

8. Aa Flows out quickly (low viscosity) and forms a brittle crust
The crust forms into jagged pieces as molten lava continues to flow underneath

9. Pahoehoe Flows slowly like molasses (high viscosity)
Has glassy surface, rounded wrinkles

10. Pillow Lava Forms when lava erupts underwater
Forms round or pillow shaped lumps

11. Blocky Lava
Cool, stiff lava that oozes from erupting vent does not travel far
Forms jumbled heaps of sharp-edged chunks

12. Volcanic Hazards Pyroclastic Flows Lahars Ash fall Lava flows
Fumaroles

13. Pyroclastic Flows
Hot ash, dust and gases ejected from the volcano flows very fast (more than 200 km/h) down slope
Temperatures can exceed 700 degree C

14. Pyroclastic Material
Volcanic Bombs- large blobs of magma that hardens in the air
Lapilli- little pebble-like bits of magma that hardens in the air
Volcanic ash- tiny glassy (silica) slivers makes up most of pyroclastic material in eruptions
Volcanic Blocks- very large pieces of rock exploded from volcano

15. Volcanic bombs

16. Lapilli
Lapilli are spheroid, teardrop, dumbbell, or button shaped droplets of molten or semi-molten lava ejected from a volcanic eruption which fall to earth while still at least partially molten.

17. Volcanic Ash

18. Volcanic blocks

19. Lahars
Lahars are volcanic mud flows made up of ash, melted snow, or water, rocks and debris that is picked up.

20. Ash Fall
Volcanic ash fall consists of ash (small tephra), which are bits of pulverized rock and glass created by volcanic eruptions.
The ash is carried by the upper winds and droped down stream from the volcano, sometimes thousands of miles away

21. Fumaroles
A fumarole is an opening in Earth‘s crust, often in the neighborhood of volcanoes, which emits steam and gases such as carbon dioxide, sulfur dioxide, hydrochloric acid, and hydrogen sulfide

22. Lava Flows

23. Types of Volcanoes Sheild Volcanoes Cinder Cone Volcanoes
Composite Volcanoes

25. Shield Volcanoes Forms from Non-explosive eruptions
Lava is thin and runny (low viscosity)
Covers large areas and has wide bases and gently sloping sides
Hawaiian Islands are shield volcanoes and Mauna Kea is taller than Mount Everest

26. Cinder Cone Volcanoes
Small volcanoes with steep slopes generally non-explosive
Made up mostly of pyroclastic material
Sometimes forms in clusters or on the sides of other volcanoes
Erodes quickly due to the loose pyroclastic material

27. Composite Volcanoes Most common type
Can form from non-explosive or explosive eruptions
Made up of layers of lava flows and pyroclastic material
Has broad bases and gets steeper towards the top

28. Craters
A funnel shape opening that generally is a circular depression in the ground caused by volcanic activity
Usually on top of a volcano
Can contain lava, pyroclastic material, water, or snow and ice in the crater

29. Calderas
A collapse of a volcano that is triggered by the emptying of the magma chamber beneath the volcano, usually as the result of a large volcanic eruption
Similar to craters, but much larger
Often fills with water
Yellowstone Natl. Park is a caldera