Fig ab. W. W. Norton

Transcription

1 VOLCANISM

2 Formation of Magma

3 Fig ab W. W. Norton

4

5 Stratovolcano Also composite cone volcano Built of layers of lava, ash and other volcanic debris Often relatively steep slopes, conical in shape, with a defined crater at the top A typical volcano what most people think of when they think volcano Characterised by explosive eruptions

6 Fig W. W. Norton

7 Ash and tephra Explosive eruption Volcanic bombs Sills Eroded cone Lava flow Dikes Side vent Lava cone Mud flows (older) Cinder cones Sequential ash and lava layers Fracturing Pyroclastic flow (nuée ardente) Old lava dome Lavas Sedimentary rocks Laccolith Lava pavement (cracked/broken) Metamorphic rocks Chimney Granite intrusion (older/cold) Contact metamorphism Magma chamber

8 Mount Rainier is potentially the most dangerous volcano in the Cascades because it is very steep, covered in large amounts of ice and snow, and near a large population that lives in lowland drainages. Numerous debris avalanches start on the volcano. The largest debris avalanche traveled more than 60 miles (100 km) to Puget Sound. Mount Rainer, Washington 4392 m

9 Mount Erebus, Antarctica 3794 m - Southern-most historically active glacier - Capped by an elliptical 500 x 600 m wide, 110 m deep summit crater with an active lava lake; continuous activity since Occasional strombolian eruptions eject lava bombs onto crater rim

10 Fig W. W. Norton

11

12 Caldera A large depression created by the collapse of a volcano Magma chamber drains Loss of structural support Collapse of overlying material

13 Crater Lake, Oregon m deep - The 7 th deepest lake in the world. Crater Lake was formed after the collapse of an ancient volcano, posthumously named Mount Mazama. This volcano violently erupted approximately 7700 years ago. That eruption was 42 times as powerful as the 1980 eruption of Mount St. Helens. The basin or caldera was formed after the top 5000 feet of the volcano collapsed. Subsequent lava flows sealed the bottom, allowing the caldera to fill with approximately 4.6 trillion gallons of water from rainfall and snow melt, to create the seventh deepest lake in the world.

14 Volcano starts to erupt. Ash and debris Full magma chamber Main explosive eruption Magma chamber empties. Newly formed caldera Collapsed blocks Empty magma chamber New volcanic cone grows. Lake fills caldera.

15 ANDRUS, Shield, 2,978 meters, Holocene? BUCKLE ISLAND, Stratovolcano, 1,230 meters, Historical DECEPTION ISLAND, Caldera, 576 meters, Historical EREBUS, Stratovolcano, 3,794 meters, Historical HUDSON MOUNTAINS, Stratovolcanoes, 749 meters, Uncertain, possibly 1985? PAULET, Cinder Cone, 353 meters, Holocene, 1850 PENGUIN ISLAND, Stratovolcano, 180 meters, Lichenometry, possibly 1905? PETER I ISLAND, Shield, 1,640 meters, Holocene ROYAL SOCIETY RANGE, Cinder Cones, 3,000 meters, Holocene? SEAL NUNATAKS GROUP, Pyroclastic Cones, 368 meters, Historical SIPLE, Shield, 3,110 meters, Holocene? TONY MOUNTAIN, Shield, 3,595 meters, Holocene? UNNAMED SCORIA CONES, 2,987 meters, Holocene? UNNAMED SUBMARINE VOLCANO, -500 meters, Holocene? UNNAMED SUBMARINE VOLCANO, Uncertain, possibly 1876 WAESCHE, Shields, 3,292 meters, Holocene?

16 Deception Island, Antarctica -14 km wide -Last known eruption 1970

17 Cinder Cone A simple volcano built from blobs of lava ejected from a single vent

18 Paricutin cinder cone, western Mexico - Born" on Feb. 20, 1943, in the field of a poor Mexican peasant who was planting corn when he saw flames begin shooting out of a nearby crack in the ground. - Within several years, Paricutin grew to a height of more than 410 m - For a time, it was Mexico's main tourist attraction. - Although Paricutin's eruptions consisted mainly of cinders for several years, it eventually emitted a lava flow that covered dozens of square miles of the surrounding countryside. - Only nine years after eruptions initiated, Paricutin went extinct and has remained inactive since 1952.

19 Shield Volcano Built from countless outpourings of fluid lava flows Large, convex, shield-shaped structures Fluid lava can spread far distances Characterised by quiet eruptions

20

21 The Island of Hawaii is made up of five volcanoes: Kohala, Mauna Kea, Hualalai, Mauna Loa, and Kilauea. Fig W. W. Norton Higher than the highest mountain: The distance between the ocean floor and the summit of Mauna Loa volcano (Hawaii) is greater than the height of Mount Everest above sea level; And it s heavy too!

22 Different Sizes 9 km 150 km Shield volcano (e.g. Hawaii) 3 km 15 km Composite volcano (e.g. Vesuvius) 0.3 km 1.5 km Cinder cone (e.g. Sunset crater)

23 Basaltic flow Andesitic flow Rhyolitic dome Rhyolitic spire

24 Flood Basalts and Ocean Plateaus Bulbous head of a mantle plume Very large outpouring Very fluid magma which can travel long distances

25 Fig a W. W. Norton

26 Krakatoa, p. 283 Stratospheric haze Fig a Rising column Falling lapilli Collapsing column W. W. Norton Nuée ardente

27 Volcanoes are good! Produced our atmosphere Volcanic soil is very fertile Beautiful scenery Mineral resources Diamonds, copper, gold, lead, zinc, etc. Pumice, BBQ rocks, aquarium stones Volcanic mud used in drilling Geothermal heat Geologic time markers Krakatoa p. 294 Possibly where life on Earth began ocean vents Eruptions make for a good story line!

28 Hot new property for sale!

29

30 The big bang The force of the eruption flattens buildings and forests When Krakatoa erupted the blast was heard as far away as Australia (a distance comparable to the width of Canada) Fig abc W. W. Norton Krakatoa, p. 160

31 Mount St. Helens Before Last eruption May 18, Krakatoa, p. 297 After

32 Hot ash is big trouble Mount Vesuvius, Italy, A.D. 79 destruction of Pompeii and other towns 5 8 m of hot ash buried town Fig c Stephen Marshak

33 Pyroclastic Debris Largest falls close to vent, smallest can travel around the world and stay in atmosphere for many years Towns get buried Abrasive, toxic and difficult to clean up Danger to aircraft sandblasted windshields, sulfuric acid, melts in engine and resolidifies Toxic to soil Inhalation hazard A rock on the noggin hurts It travels fast: km/hr = pyroclastic surge or flow On December 15, 1989, a KLM flight carrying 231 passengers flew into a cloud of ash that had erupted from Alaska's Redoubt volcano and drifted 150 miles away. All four of the engines lost power and the plane dropped nearly two miles in altitude before the crew could restart the engines. The plane sustained $80 million in damages. In 1995, an international network of Volcanic Ash Advisory Centers was established to counter the increasing threat.

34 Fig Scott, K.M., Wolfe, E.W., and Driedger, C.L., Hawaiian Volcano Observatory, U.S. Geological Survey

35 Tsunami Krakatoa, 1883 almost 40,000 killed

36 Toxic Gases Lake Nyos, Cameroon, west Africa Hotspot volcano crater filled with water Dense CO 2 slowly being released by volcano August 21, 1986 lake turned over CO 2 poured into town Not toxic but asphyxiates 1742 people and 6000 cattle killed

37 A Link to Climate Change Early atmosphere formation Eruption of ash and gases affects radiation balance 1815 Tambora (Indonesia), largest in a millenium, 1816 the year without summer, New England recorded snow in June and frosts through summer USGS discovered volcano under West Antarctic ice sheet broad regional heating Lead to faster ice movement Ice sheet collapse and rise in sea level Earth s lower albedo Change in ocean currents

38 Volcanic eruption 92,000 - Mount Tambora, (Indonesia, 1815) 40,000 - Mount Pelée, (Martinique, 1902) 36,000 - Krakatoa, (Indonesia, 1883) 23,000 - Nevado del Ruiz, (Colombia, 1985) 18,000 - Mount Vesuvius, (1631) 15,000 - Unzen, (Japan, 1792) 10,000 - Kelut, (Indonesia, 1586) 9,350 - Laki, (Iceland, 1783) 3,600 - Mount Vesuvius, (79) 1,680 - Soufrière, (St. Vincent, West Indies, 1902) 1,000 - Cotopaxi, (Ecuador, 1887) Mount Pinatubo (Philippines, 1991) Nyiragongo, (Congo, 2002) 57 - Mount St. Helens (Washington, 1980) A supervolcano that erupted at Lake Toba 74,000 years ago is thought to have reduced the global modern human population to less than 10 thousand individuals; see Toba catastrophe theory. Fig W. W. Norton Krakatoa, p. 307

39 Primary Cause of Death Volcano Country Year Pyroclastic Flow Lahar Tephra Landslide Tsunami Gas Kelut Indonesia ,000 Vesuvius Italy 1631 >4,000 Raung Indonesia 1638 >1,000 Merapi Indonesia Awu Indonesia 1711 ~3,000 Oshima Japan ,481 Makian Indonesia 1760 ~2,000 Papadanyan Indonesia ,960 Posteruptio n Starvation Gamalama Indonesia ,300 Lakagígar (Laki) Iceland ,340 Asama Japan ~1,400 Unzen Japan 1792 ~15,000 Mayon Philippines ,200 Tambora Indonesia ,000 80,000 Galunggung Indonesia ,000 Nevado del Ruiz Colombia ,000 Awu Indonesia ,000 Cotopaxi Ecuador 1877 >300 Krakatau Indonesia 1883 ~5,000 ~31,417 Ritter Papua New Guinea ,000 2 Awu Indonesia ,532 3 Soufrière St. Vincent ,680 Mount Pelée Martinique ,000 Santa Maria Guatemala 1902 ~1,500 4 Taal Philippines ,335 5 Kelut Indonesia ,110 Merapi Indonesia ,369 Rabaul Papua New Caldera Guinea Papua New Lamington ,942 Guinea Hibok- Philippines 1951 >500 Hibok Agung Indonesia 1963 >1,148 7 El Chichón Mexico 1982 >2,000 Nevado del Ruiz Colombia 1985 >23,000 Lake Nyos Cameroon ,700 Mount Pinatubo Philippines >

40 Predicting Volcanic Eruptions Changes in heat flow Changes in shape Earthquake activity Increased gas emissions and steam

41 Avoiding Fatalities Stay out of their way Evacuation Divert flow

42

43