What are you so afraid about?

Pierce County—Earthquake and  Volcano country Carolyn Driedger y g US Geological Survey

Pierce County Disasters 1980 - 2012

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1980- Volcanic eruption, Mt. St. Helens 1983- Storms & flooding 1989 Rain, 1989R i fl flooding, di & mudslides d lid 1990- Flooding, severe storm 1993- Inaugural Day storm 1994 Fishing 1994Fi hi economic i di disaster t 1996- Storms/high winds/flooding 1997- Ice & snow storms; flooding 2001 Nisqually 2001Ni ll earthquake th k 2003- Storms and flooding 2006- Wind storms, flooding, tidal surge, l d lid landslides, & mudslides d lid 2007- Storm, landslides, mudslides, flooding 2009- Wind storm, almost hit record snow 2011 Winter 2011Wi t storm, t flooding, fl di landslides, and mudslides 2012- January Ice Storm, power outages

Ring of Fire g 90% of all earthquake energy released worldwide ld id is released on the Pacific Ring of Fire

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Plate tectonics is the source of earthquakes and volcanoes.

Tectonic Plates

Geology influencing earthquakes in PNW

 Tectonic Plates  

Pacific Ring of Fire Fi Juan de Fuca Plate

 Subduction zone:

A convergent g plate p boundary where one plate subsubducts beneath the other, th usually ll because it is denser.

Earthquakes q Washington g averages g about 2000 earthquakes per year.

Three locations of Washington earthquakes:

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Deep Earthquakes (along the subduction plate) Cascadian Subduction Zone Crustal (shallow) Our geology impacts the types and frequencies of quakes in our area

Major Fault Zones in Puget Sound

 There are many faults in

Western Washington, most are invisible to us  There are 13 major faults

in the Puget Sound Region  Tacoma Fault is in our

yard  Liquefaction  Soft soils are prone to

earthquake damage

Crustal Earthquakes

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Crustal M Magnitude it d up to t 7 7.5 5 approximately every 125 250 years 125-250 L t significant Last i ifi t quake: k 7.5 (1872 )

Intra--plate (Deep) Earthquakes Intra

• • • •

Moderate 6.5— 6.5—6.8 O Occurs ~ every 3030-50 years 1949, 1965, 2001 Nisqually was 6.8 A major major j event 7.0— 7.0—7.5 occurs ~ every y 30 y yrs 1949 quake was 7.1

Cascadia Fault Earthquakes Quick slippage of the subducting slab

Cascadia Subduction Zone – Magnitude 8-9 +along coast, with minutes of shaking. Many a y aftershocks. a te s oc s Approximately every 400— 600 years Last documented: 9.0 magnitude Jan. 26, 1700 @ 9 PM

q Definition of LiquefactionTransformation of loose sediment or soil into a fluid state as a result of increasing the pressure of the fluid in between the grains due to strong ground shaking shaking.

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Thirteen major volcanoes g of the Cascade Range

Subduction Animation by Jenda Johnson

Mount Rainier is an ACTIVE volcano.

• Last activity in 19th century. (eruption 1,100 years ago; 1894-95 steam activity) • Seismically active (earthquakes below base of volcano indicate hot rock) • Active hydrothermal system (hot springs, steam) • Location on active subduction zone ((magma g still forming)

With Virtual Certainty…

…Mount Mount Rainier will erupt again. again •There is a wide range of possibilities: • Minor eruptions of steam and ash affecting summit area only. • Larger eruptions, when hot rock melts snow and ice and cause lahars (volcanic mudflows) that travel down the river valleys to areas distant from the volcano volcano.

At present, Mount Rainier shows no signs g of volcanic unrest.

•When unrest is detected, scientists will increase monitoring efforts. •Public officials will notify the public via the media.

Volcanoes give us warning signs

•Volcanoes often show signs that they are getting ready to erupt days to months or more in advance. •Scientists evaluate signs of unrest and look for: •Increased emission of volcanic gases •Increased earthquake activity •Swelling of the volcano.

Volcanic Ash

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• Particles of shattered rock. • Falls F ll att normall air i temperature at distance from the volcano. • Irritates e eyes, es breathing difficult, reduces visibility, abrasive, clogs filters. filters • Non poisonous to touch or breathe. • Some risk to people with existing respiratory problems.

L Lava Flows Fl • Destroy all in their path by burial and fire. • Melt some snow and d ice. i • Collapse on steep slopes l and d cause Pyroclastic flows

Pyroclastic Flows • Avalanches of hot gases and rock. • Form by collapse of lava flows or eruption columns. • Destroy D t all ll in i their th i path by burial, burning and asphyxiation. h i ti • Melt snow and ice and indirectly cause lahars.

Pyroclastic Flow on Mount Unzen, Japan 1991

Debris flows and Lahars •Slurries of mud, boulders and water •Speeds of 40 mph are common •Travel to areas distant from the volcano. •Formed F d by b •Volcanically-melted snow and ice •Landslides •Glacier-related floods

Lahar at Semeru Volcano, Indonesia by Franck Lavigne

Post-lahar sedimentation lasting centuries t i can be b more destructive d t ti than actual lahar.

Mount Rainier report of the 600 year old Electron Mudflow? “…Tacobed’s head broke open and the lake on top spilled out place where Orting g and the water rushed down. It filled the p now is and left the prairie covered with bubble-filled stones.”

Paths of Some Major Lahars at Mount Rainier 5 600 years ago to present 5,600 present.

A.D. 1503 Electron Mudflow p Deposits • • • •

78,000 residents >11% over age 65 39% renter occupied 3,900 businesses generating $16 billion annually. • Many critical facilities

Sediment from the Osceola and other ud o s co contributed t buted to tthe e infilling go of so some e mudflows Puget Sound inlets

Areas at Risk from lahars—most significant hazards from Mount Rainier eruptions eruptions. Lahar a a Hazard a a d Zones: o es But, we don’t know the size of the next lahar!

What You Can Do-• Learn—Become knowledgeable about volcano issues. Learn whether you live, work or go to school in a volcano hazard zone. q public officials how they p y • Inquire---Ask advise you to respond. • Plan---For how you and your family will respond in the event of any natural disaster.

What to do when an eruption Is underway: -If you are in a lahar hazard zone, get to high ground and to shelter. -If you are above a lahar hazard zone, shelter in place.

The BEST reason to be prepared prepared…

When people become knowledgeable about natural processes, they can prepare for hazards, then live with greater safety and comfort in this corner of paradise!

Visit the USGS Cascades Volcano Homepage:

http://volcanoes.usgs.gov/observatories/cvo/ Updated Website in progress!!!

Activity Report Link

Hot Stuff Current Events Choose a volcano

Register to receive the weekly Volcano Notification System y (VNS) ( ) Update. p http://volcanoes.usgs.gov/vns/