sign in sign up
<<
Home , Mount Unzen, Tacoma Fault

What are you so afraid about? Pierce County— and country

Carolyn Driedger US Geological Survey Pierce County 1980 - 2012 1980- Volcanic eruption, Mt. St. Helens 1983- Storms & flooding 1989- RiRain, fldiflooding, & mudslid es 1990- Flooding, severe storm 1993- Inaugural Day storm 1994- Fishi ng econom ic disas ter 1996- Storms/high winds/flooding 1997- Ice & snow storms; flooding { 2001- Nisquall y earth quak e 2003- Storms and flooding 2006- Wind storms, flooding, tidal surge, land slid es, & mud slid es 2007- Storm, , mudslides, flooding 2009- Wind storm, almost hit record snow 2011- Wint er st orm, fl oo ding, landslides, and mudslides 2012- January Ice Storm, power outages Plate tectonics is the source of Ring of Fire and volcanoes.

90% of all earthquake energy released worldw ide { is released on the Pacific Ring of Fire Tectonic Plates Geology influencing earthquakes in PNW

 Tectonic Plates  Pacific Ring of Fire 

 Subduction zone: A converggpent plate boundary where one plate sub-sub- ducts beneath the other, usuall y because it is denser. Earthquakes

Washingggton averages about 2000 earthquakes per year.

Three locations of Washington earthquakes: 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

 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

Crustal -  ,, MitdMagnitude up t75to 7.5 approximately every 125-250 years

LtiifitLast significant quak e: 7.5 (1872 ) IntraIntra--plateplate (Deep) Earthquakes

• Moderate 6.5—6.5—6.86.8 • OO30ccurs ~ every 30-50 years • 1949, 1965, 2001 Nisqually was 6.8 • A mmaajor event 7.0—7.5 occurs ~ every 30 yrs 1949 quake was 7.1 Cascadia Fault Earthquakes Quick slippage of the subductingslab

Cascadia Subduction Zone – Magnitude 8-9 +along coast, with minutes of shaking. Maayatesocsny aftershocks. Approximately every 400— 600 years Last documented: 9.0 magnitude Jan. 26, 1700 @ 9 PM Definition of Liquefaction- Transformation 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. {

{ { Thirteen major volcanoes of the Cascade Range

Subduction Animation by Jenda Johnson 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 ((gmagma still forming) With Virtual Certainty…

…Mount Rainier will erupt 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 (volcanic mudflows) that travel down the valleys to areas distant from the volcano. At present, Mount Rainier shows no signs 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.

• Particles of shattered rock. • FllFalls at normal ai r temperature at distance l from the volcano. • Irritates ey es, breathing difficult, reduces visibility, abrasive, clogs filters. • Non poisonous to touch or breathe. • Some risk to people with existing respiratory problems. LFlLava Flows

• Destroy all in their path by burial and fire. • Melt some snow andid ice. • Collapse on steep sldlopes and cause Pyroclastic flows Pyroclastic Flows

• Avalanches of hot gases and rock. • Form by collapse of lava flows or eruption columns. • DtDestroy a llithill in their path by burial, burning and asphitihyxiation. • Melt snow and ice and indirectly cause lahars. on Mount Unzen, 1991 Debris flows and Lahars

•Slurries of mud, boulders and water •Speeds of 40 mph are common •Travel to areas distant from the volcano. •FdbFormed by •Volcanically-melted snow and ice •Landslides •Glacier-related floods at Semeru Volcano, Indonesia by Franck Lavigne Post-lahar sedimentation lasting centituries can b e more d dtestructi ve 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 and the water rushed down. It filled the ppglace where Orting 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.

A.D. 1503 Electron Mudflow 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 mudfl ow s con tri buted to th e infillin g of some Puget Sound inlets Areas at Risk from lahars—most significant hazards from Mount Rainier eruptions.

Laaahar H aadoesazard Zones: 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. • Inquire---Ask ppyublic officials how they advise you to respond. • Plan---For how you and your family will respond in the event of any natural . 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…

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 Syy()pstem (VNS) Update. http://volcanoes.usgs.gov/vns/