1. Unit 2 : Inside Earth
Volcanoes!!!

2. Which releases more energy?
Atomic bomb
volcano

3. If you voted for the volcano you are right!
A volcanic explosion is 10,000 times stronger than the force of the first atomic bomb.
The force can kill people, plants and animals
Poisonous gases can kill if breathed in by people and animals
Tsunamis, floods, rock falls, mudflows can be triggered
Volcanic ash can stall out jet engines
Lava flows can start fires, kill people, and bury towns

4. 1980-2008 Volcano Stats Number of events: 140
Number of people killed: 25,197
Average people killed per year: 869
No of people affected: 4,080,791
Average people affected per year: 140,717
Economic Damage (US$ X 1,000): 2,870,769
Economic Damage per year (US$ X 1,000): 98,992

5. What are volcanoes?
Volcanoes are areas of the Earth’s surface through which magma and volcanic gases pass.
Most volcanoes are found along the Ring of Fire , an area that circles the Pacific Ocean

6. Two Kinds of Eruptions Most common type
Non-explosive
Explosive
Most common type
Produce huge amounts of relatively calm lava
Found on much of the seafloor and Northwestern US
Much rarer than non-explosive.
Incredibly destructive!!!
Clouds of hot debris, ash and gas rapidly shoot out of the volcano
Volcanic ash produced by explosive volcanoes can get stuck in the atmosphere and circle the Earth for years
In a matter of seconds, an explosive volcano can demolish an entire mountainside

7. Two Kinds of Eruptions
Non-Explosive
Explosive

8. What is inside a volcano?
If you could look inside a volcano, you would see the features on the graphic.
Magma chamber: a body of molten rock deep underground that feeds the volcano
Vents: cracks in the Earth’s surface though which magma is released during an eruption

9. What erupts from a volcano?
Magma erupts as either lava or pyroclastic material
Lava is the liquid magma that flows from a vent
Pyroclastic material forms when magma is blasted into the air.

10. Four Types of Lava Aa lava Low viscosity Pours out quickly
Forms a brittle crust
The crust is torn into jagged pieces as molten lava continues to flow underneath
Named by the first person to try to walk on it!

11. Four Types of Lava Pahoehoe High viscosity
Flows slowly – like wax dripping from a candle
Glassy, wrinkled surface

12. Four Types of Lava Pillow Lava Low viscosity Quick flowing
Underwater eruptions
Forms rounded lumps that are in the shape of pillows

13. Four Types of Lava Blocky Lava High viscosity Flows slowly
Oozes from a volcano and forms jumbled heaps of sharp edged chunks
Does not travel far from the erupting vent

14. Four Types of Pyroclastic Material
Volcanic Bombs: large blobs of magma that harden in the air.
Lapilli: pebble-like bits of magma that hardened before they hit the ground. Means “little stones” in Italian
Volcanic ash: forms when gases in magma explode. Most pyroclastic material is ash
Volcanic blocks: pieces of solid rock erupted from a volcano. Larges pieces.

15. Pyroclastic Materials

16. Pyroclastic Flows
One particularly dangerous type of volcanic flow is called a pyroclastic flow.
Enormous amounts of hot ash, dust, and gases are ejected from a volcano.
Travel at speeds faster than hurricane-strength winds!

17. The Effects of Volcanic Eruptions
In 1816, a man in Connecticut laid his clothes out to dry overnight. When he woke up, they were frozen solid. This would not be weird if it wasn’t June 10!!
What happened??
A volcanic island on the other side of the world had sent a cloud of volcanic ash into the atmosphere and cause the “Year Without A Summer”
Volcanic ash and gasses can block sunlight and cause global temperatures to drop!

18. Different Types of Volcanoes
While volcanic eruptions can cause major changes to the Earth’s climate, the changes to the Earth’s surface are more familiar.
There are three basic types of volcanoes
Shield
Cinder Cone
Composite

19. Shield Volcanoes
Built of layers of lava released from repeated non-explosive volcanoes.
Gently sloping sides
Can be enormous
Mauna Kea in Hawaii

20. Cinder Cone Volcanoes
Made of pyroclastic material produced from moderately explosive volcanoes.
Steep slopes
Small and usually erupt for a short period of time.
Occur in clusters
Quick erosion
Paricutin in Mexico

21. Composite Volcanoes Most common type
Form from explosive eruptions of pyroclastic material followed by flows of lava.
Broad bases and steep sides
Mt. Fuji in Japan, Mt. St. Helens in US

22. Other types of volcanic landforms
Craters: funnel shaped pit a the top of the central vent of a volcano.
Caldera: a large, semi-circular depression that forms when the magma chamber partially empties and the roof collapses.

23. Causes of Volcanic Eruptions
Magma forms in the deeper regions of the Earth’s crust and in the uppermost layers of the mantle.
Magma is a very hot, plastic rock that flows slowly.

24. How do volcanoes form
Usually the pressure from the rock above keeps the magma’s atoms so tightly compressed that the rock cannot melt.
When this pressure is released, such as at the boundary of tectonic plates, the magma slowly rises to the surface

25. Where do volcanoes form?
Tectonic plate boundaries
Divergent boundaries --- plates move apart
15% of volcanoes
Mid-Ocean ridges
Convergent boundaries --- plates collide
80% of volcanoes
Subduction
Hot Spots
A volcanically active area far from tectonic plate boundaries
5% of volcanoes
Hawaii

26. Divergent Boundary Volcano

27. Convergent Boundary Volcano

28. Hot Spots!