1. Agenda: Tuesday April 2 nd 1) Mental Mon(Tues)day 2) Hand in Geological Clocks!!!! 3) Volcanoes

2. Phys Geo So Far… Layers of the earth Continental Drift Tectonic Plates Tectonic Processes Geological Eras

3. Still to come… Natural disasters – Volcanoes – Earthquakes Assignment Rock Cycle Glaciation Soils Weather/Climate

4. VOLCANOES!!!!

5. cool fact! The term “volcano” is from the Latin Volcanus or Vulcan, the Roman god of fire.

6. neat fact! The most formidable volcanoes are called supervolcanoes. A supervolcanic eruption can cause worldwide climatic changes, such as a drop in global temperature due to the release of tons of ash particles into the atmosphere. These monsters rear their ugly heads only ever few hundred thousand years, however. One of the biggest is in Yellowstone National Park, and scientists say it may be due for another eruption. supervolcanoes

7. wild fact! The largest volcanic eruption ever observed was of Mount Tambora, on the island of Sumbawa, in Indonesia. Its eruption in 1815 killed about 100,000 people. Indonesia is thought to have the largest number of historically active volcanoes – a total of 76, according to the U.S. Geological Survey.Mount Tambora

8. weird fact :s Hundreds of years ago, the Aztecs of Mexico and the people of Nicaragua believed gods lived in lava lakes. They would sacrifice beautiful young girls to these powerful gods.

9. sad fact  During the past 400 years, nearly a quarter of a million people have been killed as a direct result of volcanic eruptions. Indirect aftereffects such as famine, climate change, and disease most likely have tripled that number

10. What is a Volcano?

11. A Volcano is an opening (crack) in the earth’s crust where lava reaches the surface

12. How are they formed? Volcanoes are formed when molten (sticky rock called magma) forces its way through a crack in the Earth’s crust. moltenmagma The magma that spills out of the crater on the top of the volcano is called lava.craterlava ***(lava is magma that has reached the earth’s surface)

13. A lake of boiling lava on an island in the South Pacific Ocean http://www.youtube.com/watch?v=IAxj2ob_J oU http://www.youtube.com/watch?v=IAxj2ob_J oU

14. Active vs. Dormant vs. Extinct A volcano is active when it erupts often. When a volcano is dormant, it has not erupted for a long time – but it might in the future. A volcano is extinct when it hasn’t erupted for at least 100,000 years.

15. How does it happen?

16. We know the earth’s crust is made up of plates, and we know that these plates move…

17. If you look at the location of volcanoes in relation to these plates, you will notice some things: Many of the world’s volcanoes occur along the edges/ boundaries of the plates. Plate boundaries are among the most geologically active places on earth. Here, new rock is being both created and destroyed, so this is where most of the world’s volcanic eruptions and earthquakes occur.

18. Volcanoes are generally found where tectonic plates are 1) diverging or 2) converging, or from 3)hot spots ………………………..

19. Sidenote: (Volcanoes are usually not created where two tectonic plates slide past one another…..this type of movement causes…..???)

20. Plate Tectonics & Hotspots Divergent plate boundaries Convergent plate boundaries Hotspots The pulling apart of plates, causing molten rock to come to the top of the mantle. Causes mainly submarine volcanic activity and creates new oceanic crust. The collision of plates, causing Subduction or one plate to submerge beneath the other late to Located away from tectonic plates, over mantle plumes where pipes vent magma. Volcanoes formed over hotspots become dormant and new ones are formed when plates move overhead.

21. 1. Divergent Plate Boundaries Most divergent plate boundaries are at the bottom of the oceans, causing most of the volcanic activity to be under water, thus forming new seafloor. (ie. Mid Atlantic Ridge) -Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, Iceland.Iceland

22. 2. Convergent Plate Boundaries When two plates collide, causing the one plate to submerge under the other plate (called subduction). In the case of oceanic-continental, a deep trench just off shore is formed. When the thick magma reaches the surface, a volcano is formed. *This is what caused the typical Ring of Fire volcanoes.* Oceanic - Oceanic convergenceContinental - Continental convergenceOceanic - Continental convergence

23. In the theory of plate tectonics most of the geological characteristics are explained by interaction among plates. theory of plate tectonicsplates However, some of most spectacular formations are caused by "hot spots" which are situated far from the edges of tectonic plates.tectonic plates

24. 3. Hotspots A hotspot is a place in the middle of a tectonic plate where hot magma rises (called a mantle plume) until it reaches the crust. Magma then flows out.

25. Pacific Ring of Fire The Pacific Ring of Fire is an area of frequent earthquakes and volcanic eruptions circling the basin of the Pacific Ocean. Result of plate tectonics and the movement and hitting of crustal plates.

26. Pacific Ring of Fire -The Pacific Ring of Fire is an area where large numbers of earthquakes and volcanic eruptions occur in a 40,000km horseshoe shape. -Contains 452 volcanoes, with over 75% of worlds active and dormant volcanoes.

27. Notes to fill in on your handout…

28. Inside a Volcano

29. The magma chamber is a collection of magma inside the Earth, below the volcano. The main vent is the main outlet for the magma to escape. Secondary vents are smaller outlets through which magma escapes. The crater is created after an eruption blows the top off the volcano.

30. There are 3 types of Volcanoes Shield Volcano Cinder Cone Volcano Composite Volcano

31. Shield Volcano A gently-sloped volcano (large volcano but not very tall) Lava is thin, runny and spreads a long way from the vent 95% lava and 5% ash

32. Shield Volcano Diagram

33. Composite (Strato) Volcano Usually quite tall Made up of alternating layers of lava and ash (other volcanoes just consist of lava)…. Results in steeper sides Have a pyroclastic flow (a mixture of hot steam, ash, rock and dust).

34. Composite Volcano Diagram

35. Cinder Cone Most common Smallest type Steep, straight sides Often have very large summit craters Made of cinders (melted volcanic rock that has cooled down)

36. Cinder Cone Volcano Diagram

37. Real World Examples of Volcano Types…

38. What kind of volcano is this?

39. Diamond Head, Hawaii is an eroded Cinder Cone volcano Early sailors mistakenly thought shining calcite crystals inside the rocks were diamonds, leading to the incorrect name. Diamond Head formed when hot magma rising up a tube hit ocean water, causing large explosions that threw exploded magma particles into a broad ring.

40. What kind of Volcano is this?

41. Mount St. Helen’s is a composite (strato) volcano - Mount St. Helens (Washington) is most notorious for its catastrophic eruption on May 18, 1980- the deadliest and most economically destructive volcanic event in the history of the United States.its catastrophic eruption -an active volcano! California

42. Mt St. Helens https://www.youtub e.com/watch?v=- H_HZVY1tT4 https://www.youtub e.com/watch?v=- H_HZVY1tT4

43. What kind of volcano is this?

44. Kohala is a shield volcano. Kohala is the oldest of the volcanoes that make up the Island Of Hawaii. Kohala is considered to be extinct because it has not erupted for 60,000 years. Hawaii

45. Positive and negative effects of an eruption PositiveNegative -Dramatic scenery created by volcanic eruptions attracts tourists (income) -Many lives can be lost as a result of a volcanic eruption. -Lava and ash deposited can provide valuable nutrients for the soil. Human and natural landscapes can be destroyed and changed forever.

46. 2010- A volcanic eruption near the Icelandic Volcano Eyjafjallajökull glacier in southern part of Iceland. http://www.youtube.com/watch?v=UmEJ RmBcM0o http://www.youtube.com/watch?v=UmEJ RmBcM0o