Other volcanic features Flood basalts Largest volcanic events

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Other volcanic features • Flood basalts – Largest volcanic events in terms of volume

Other volcanic features • Flood basalts – Largest volcanic events in terms of volume – Volatiles, viscosity are low, so not very explosive – Cover large areas w/ thick layers of lava • Lava domes – Hardened dome/plug of magma cools quickly – Can form in hours, continue for years, decades

Flood Basalts

Flood Basalts

Lava Domes Lava Dome, Mt. St. Helens

Lava Domes Lava Dome, Mt. St. Helens

Volcanic Hazards

Volcanic Hazards

Outline • Types of volcanic hazards

Outline • Types of volcanic hazards

Volcano Classification • Active: currently erupting or has erupted in historical time • Dormant:

Volcano Classification • Active: currently erupting or has erupted in historical time • Dormant: presently inactive but may erupt again (examples: Cascades) • Extinct: not active, not expected to be active for long time in future

Cumulative Deaths Due to Volcanic Hazards in past 2000 years

Cumulative Deaths Due to Volcanic Hazards in past 2000 years

Causes of Deaths

Causes of Deaths

How bad can it be? • • • 1815 1822 1826 1883 1902 1919

How bad can it be? • • • 1815 1822 1826 1883 1902 1919 1951 1982 1985 Indonesia Martinique Guatemala Indonesia New Guinea Mexico Columbia 92, 000 died* 5, 500 killed 3, 000 killed 36, 417 killed 29, 025 killed 6, 000 killed 5, 110 killed 2, 942 killed 1, 700 killed 23, 000 killed

Pyroclastic Flow • Most deadly of all hazards • Superhot, fast moving cloud of

Pyroclastic Flow • Most deadly of all hazards • Superhot, fast moving cloud of volcanic gas, steam, debris • 200 -700 degrees C, 80 km/hr (hurricane speeds!)

Generation of pyroclastic flow • Eruption column collapse • Dome collapse • Directed blasts

Generation of pyroclastic flow • Eruption column collapse • Dome collapse • Directed blasts

Pyroclastic flows Mayon, Philippines, 1984

Pyroclastic flows Mayon, Philippines, 1984

Effects of Pyroclastic Flows • Destroys nearly everything in path – Structures – Burial

Effects of Pyroclastic Flows • Destroys nearly everything in path – Structures – Burial of sites – Burn forests, crops, structures – Melt snow to form lahars

Building destruction Remnant of building after eruption of El Chichon, Mexico in 1982 Note

Building destruction Remnant of building after eruption of El Chichon, Mexico in 1982 Note reinforcement rods bent in direction of flow

Effects of pyroclastic flows Mt. St. Helens - forest destruction

Effects of pyroclastic flows Mt. St. Helens - forest destruction

Effects on people • • Physical impact Burns Inhaling superhot gases Usually quick death

Effects on people • • Physical impact Burns Inhaling superhot gases Usually quick death

Examples • Many examples of devastating pyroclastic flows – Unzen, Japan – Chichon, Mexico

Examples • Many examples of devastating pyroclastic flows – Unzen, Japan – Chichon, Mexico – Mt. Pelee, Caribbean*

Mt. Pelee • 1902 -1903, 1929 -1932 significant pyroclastic flows • Many from directed

Mt. Pelee • 1902 -1903, 1929 -1932 significant pyroclastic flows • Many from directed blasts, deadliest in 1902 – Viscous magma filled crater – May 1902, several pyroclastic flows, traveling ~190 km/hr – Destroyed St. Pierre (~30, 000 people) and other towns in area

Mt. Pelee Large area affected by 1902 pyroclastic flows

Mt. Pelee Large area affected by 1902 pyroclastic flows

Eruption Debris • Includes cloud, bombs, ash fall • Bombs kill small # of

Eruption Debris • Includes cloud, bombs, ash fall • Bombs kill small # of people every year • Clouds – Planes fly into cloud - dangerous • Over 25 years, ~60 jets damaged • Ash fall – Bury cities

Ash fall hazards Roof collapse Mid-Afternoon daylight gone Water systems can clog

Ash fall hazards Roof collapse Mid-Afternoon daylight gone Water systems can clog

Kamchatka eruption, seen by space shuttle Cloud Hazard Ash from Mt. Spurr traveled around

Kamchatka eruption, seen by space shuttle Cloud Hazard Ash from Mt. Spurr traveled around for days (satellite image)

Example - Mt. Vesuvius 79 AD • Cause of volcano: subduction • Region near

Example - Mt. Vesuvius 79 AD • Cause of volcano: subduction • Region near Pompeii also had earthquakes, but city of ~20, 000 people not deterred to move • Significant volume of material erupted (4 km 3) in first wave – Pompeii buried by ash/pumice 3 m deep • Later pyroclastic flows continued to bury city

Vesuvius Remains of Pompeii after 79 AD eruption

Vesuvius Remains of Pompeii after 79 AD eruption

Tsunami • Wave caused by undersea vertical displacement (like earthquakes) • Volcanic eruption can

Tsunami • Wave caused by undersea vertical displacement (like earthquakes) • Volcanic eruption can also cause tsunami – Pyroclastic flow or lava dome avalanche – Collapse of cone or crater

Example - Krakatau 1883 • • • Stratovolcano between Java and Sumatra Subduction zone

Example - Krakatau 1883 • • • Stratovolcano between Java and Sumatra Subduction zone Collapse led to tsunami ~35 m (115 ft) Death toll ~36, 000 New cone appeared in 1927

Collapse of Krakatau Anak Krakatau

Collapse of Krakatau Anak Krakatau

Lahars • Mudflow of volcanic debris, produced when pyroclastic debris or lava mix with

Lahars • Mudflow of volcanic debris, produced when pyroclastic debris or lava mix with rain, snow, ice, lakes • Can travel quickly (40 mph) and significant distances (10 s of miles)

Dark pathways - lahars triggered by Mt. St. Helens eruption, 1985 “Cloud” upriver: lahar

Dark pathways - lahars triggered by Mt. St. Helens eruption, 1985 “Cloud” upriver: lahar traveling down riverbed in Guatemala

Home destroyed from lahar - Mt. Unzen, Japan lava dome collapse and later rains,

Home destroyed from lahar - Mt. Unzen, Japan lava dome collapse and later rains, 1993

Example - Nevado del Ruiz 1985 • Colombian volcano, small glacier on top •

Example - Nevado del Ruiz 1985 • Colombian volcano, small glacier on top • Small eruption caused melting, sending mud down the mountain • Covered most of town of Armero with ~26 ft thick mud – Killed ~22, 000

Nevado del Ruiz, 1985 River valley with lahar remains Town of Armero

Nevado del Ruiz, 1985 River valley with lahar remains Town of Armero

Famine • Indirect hazard • Eruptions change climate – Can harm plants, animals

Famine • Indirect hazard • Eruptions change climate – Can harm plants, animals

Iceland eruption, 1783 • Fissure eruption of basalt • Released gas rich in Si.

Iceland eruption, 1783 • Fissure eruption of basalt • Released gas rich in Si. O 2 and fluorine – Slowed grass growth and added significant amounts of fluorine to grass – Killed significant population of livestock • ~20% of Iceland population died due to famine

Tambora, 1815 • Indonesian volcano, most violent eruption in last 200 years • Significant

Tambora, 1815 • Indonesian volcano, most violent eruption in last 200 years • Significant Plinian eruption • Next pyroclastic flows (12 mi 3 of material) • Deaths in region ~90, 000 (10% during eruption, 90% later) • 1816 - year without summer – Affected global climate

Gas • Gas can escape from basaltic magmas – CO 2 gas is common

Gas • Gas can escape from basaltic magmas – CO 2 gas is common • Depending on gas, can kill plants in region • Can also be trapped in water

Example - Lake Nyos, Cameroon • Area of failed rifts with some remaining volcanic

Example - Lake Nyos, Cameroon • Area of failed rifts with some remaining volcanic activity • 1986 - gas burp from the lake – Sent rivers of gas down into valleys ~25 km (16 mi) • Effects - ~1700 deaths, no animals alive – Plants ok though

Why? • CO 2 gas leaking out of basaltic magma • Dissolved in bottom

Why? • CO 2 gas leaking out of basaltic magma • Dissolved in bottom waters of lake (held down by pressure) • Some event caused overturn – Eruption, earthquake, landslide, temp change all possible triggers • Gas release “river” ~50 m thick

Lake Nyos

Lake Nyos

Lake Nyos Efforts to pump water, gas out of lake

Lake Nyos Efforts to pump water, gas out of lake

Continued hazard? • • YES! Still some gas remaining Continues to build up Possible

Continued hazard? • • YES! Still some gas remaining Continues to build up Possible ways to pump gas out to reduce risk

Lava Flows • Not big hazards in terms of fatalities • Moves too slow

Lava Flows • Not big hazards in terms of fatalities • Moves too slow to kill people • Can destroy towns, villages

Kilauea, HI • Few lives lost • Mostly structural losses

Kilauea, HI • Few lives lost • Mostly structural losses

1973 Flows in Iceland • Lava flows threatened town, harbor • Built diverters to

1973 Flows in Iceland • Lava flows threatened town, harbor • Built diverters to control flow • Sprayed water to harden flows, move to flow in other direction away from harbor

Man vs. volcano!

Man vs. volcano!

Actually gained land improved harbor

Actually gained land improved harbor

Next Time • U. S. volcanoes and related hazards

Next Time • U. S. volcanoes and related hazards