1. Volcanic Eruptions
7.3 p

2. Inside a volcano

3. Magma chamber- holds the magma
Pipe- tube that connects the magma chamber to the surface
Vent-place where magma reaches the surface
Lava flow- area covered after the volcano erupts
Crater- the bowl shape area that forms around the central vent

4. The Eruption
Volcanoes erupt when the pressure gets too great and the gases and magma rises in the pipe. As it goes up toward the surface the pressure decreases and the gas bubbles expand so much that they form bubbles and increase in size. This increase in size exerts a force on the top of the volcano and it erupts.

5. - Volcanic Eruptions

6. Kinds of Volcanic Eruptions
Volcanoes are either quiet or explosive.
Depends on the silica content and viscosity.
Quiet eruptions: low in silica, low viscosity, flows and oozes over many kilometers produces Aa and pahoehoe
Ex: Hawaii

7. Hawaii

8. Explosive
Explosive eruptions: high in silica, high viscosity- this sticky substance does not flow in the pipe easily and it tends to get clogged causes lots of pressure to build up. Erupts and causes dust, ash, cinders, and bombs to fall. Also causes pyroclastic flows
EX: Mt. St. Helens

9. Mt. St. Helens
Mount St. Helens

10. Volcanic Hazards
Quiet eruptions cause flowing lava to flow from the vent and set fire to and burn everything in its path and cover large area with thick layers of lava.
Explosive Eruptions cause towns to be buried in volcanic ash causing roofs to collapse, plane crashes, landslides and avalanches of mud

11. Life Cycle of a volcano
Active- volcano that is erupting or has shown signs that it may erupt in the near future.
Dormant- sleeping volcano could awaken in the future and erupt again.
Extinct- dead volcano unlikely to erupt again.
Some volcanoes only erupt every several hundreds or thousands of years and are dormant for long periods of time.

12. Monitoring Volcanoes
Predicting volcanoes is an easier job than predicting earthquakes. Volcanoes give off signs to scientists such as elevation changes that can be detected with a tiltmeter, gases can be monitored, temperature changes can be detected, and earthquakes that occur close to site are watched by a seismograph.

13. 7.4 Volcanic Landforms
Pages 217 to 223

14. Landforms from Lava and Ash
Shield Volcanoes
Produced by slowly venting volcanoes that pour layer over layer of lava on top of eachother.
Cinder Cone Volcanoes
Produced by ash, cinders, and lava bombs into a high volcano
Composite Volcanoes
Combination of slow lava flows and explosive ash, cinder, and lava
Lava Plateaus
Formed by thin, runny lava that oozes out of cracks

15. Shield Volcano

16. Cinder Volcano

17. Composite Volcano

18. Lava Plateau

19. More Lava Forms Calderas Uses for volcanic soil
Huge craters formed by supervolcanoes that collapse into the magma chamber.
Uses for volcanic soil
Volcanic soil is initially barren, but after the soil breaks down it releases potassium, phosphorus, and carbon
Once broken down volcanic soil is very fertile

20. Yellowstone Caldera

21. Yellowstone Caldera

22. Yellowstone Caldera

23. Landforms From Magma Volcanic Necks Dikes and Sills
Magma from a volcano’s pipe hardens and leaves a giant “tooth” in the earth
Dikes and Sills
Dike – Formed by magma slanting through bedrock sideways
Sill – Formed when magma squeezes between horizontal layers of rock

24. Volcanic Neck (Monument Valley)

25. Dike (Stairway to Heaven, Spain)

26. Sill (Palisades, NJ)

27. Landforms from Magma Cont’d
Batholiths
Huge masses of rock formed when magma cools inside he crust
Dome Mountains
Hardened magma pushes rock above it up, creating small mountains and hills

28. Sierra Nevada Batholith

29. Dome Mts (Black Hills, SD)

30. Geothermal Activity
Comes from the Greek, “geo” means “Earth” and “therme” means “heat.”
Hot Springs
Large super-heated pools of water
Geysers
Release super-heated water at intervals when pressure builds high enough

31. Hot Springs, Iceland

32. Geysers, Old Faithful, Yellowstone