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Geologic Processes and HazardsSeptember 15th, 2011

• Geology: scientific study of Earth’s materials and processes– Materials:

– Processes:

• Geologic Processes are both internal and external.

• Geologic Processes create:

Geologic Processes create:Hazards and Resources

1) Hazards (dangerous events and conditions)

2) Resources (the materials we use to get the things we want: fuel our vehicles, power our homes, computers, construct buildings, roads, cities, vehicles etc.)

– More on this (fossil fuels, minerals, rocks, soil, water) later in the course

3) Links between internal and external geologic processes:

– internal processes create new crust, cause hazards, concentrate minerals.

– external processes carve up crust creating landforms and environments which are subjected to hazards (flooding, landslides), concentrate minerals.

Major Internal ProcessesDriven by energy (heat) in the Earth’s interior

• 1) Convection

• 2) Plate Tectonics

• 3) Rock Deformation

• 4) Crystallization

• 5) Metamorphism

Let’s look at the basics of Plate Tectonics

Plate Tectonics Theory“a widely held or coherent explanation characterizing interactions of

various phenomena that cause a certain pattern in nature.”

• Outer layers of Earth made up of ~ 12 major individual rigid plates (lithospheric/tectonic plates)

• These plates move in response to convection in the mantle

• Most geologic activity occurs near plate boundaries (3 types of boundaries)

• “Geologic activity”? = mnt blding, deformation, e-quakes, volcanoes (formation of Resources and Hazards)

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Transform Boundaryexample: San Andreas Fault

Divergent BoundariesMid-Ocean Ridge System and SFS

usually shallow focus and small earthquakes

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Fig. 12-18a, p.351

Convergent BoundariesDeep sea trenches, subduction, collision, deformation and

deep to shallow focus and stronger earthquakes

Major External ProcessesDriven by energy from the sun and from gravity.

Also create resources and hazards.

• Hydrologic cycle

• Weathering and erosion

• Deposition and Soil Formation

• Glaciers, Rivers and Streams

• Mass Movement (landslides, rock falls)

• Land-Sea Interactions/Coastal Erosion

Major External Processes“wear down Earth’s surface”

annual transfer rate in thousands of cubic kilometers

Weathering and erosionDeposition and Soil FormationGlaciers, Rivers and StreamsMass Movement (landslides, rock falls)Land-Sea Interactions/Coastal Erosion

The Hydrologic Cycle

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Geologic Hazardsresult from a combination of internal and external processes

1. Earthquakes

2. Tsunamis

3. Mass Movement

4. Volcanoes

5. Coastal Erosion / Flooding / Rising Sea Level

6. Fluvial Systems /Flooding (Later in the Course)

EarthquakesMajor dangers are from human-made structures rather than the earthquake itself.

Over 676,000 fatalities from earthquakes in the last 10 years.

• Ground Shaking: landslides, liquefaction, land subsidence, buildings, roads, bridges collapse

• Ground Displacement: damages structures lying across fault

• Flooding: tsunamis and/or “co-seismic subsidence”

• Fire: broken gas and power lines• http://en.wikipedia.org/wiki/List_of_21st_century_earthquakes#2009

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Love Waves

Sir John William Strut, aka Lord Rayleigh, a British Physicist in 1885

A.E.H. Love, an British Mathematician in 1911

Fig. 9-15, p.260

Amount of damage controlled by what? StrengthRelative ProximityFoundationBuilding Type

Type of bedrock / foundationLiquefaction in Monterey Bay, 10/17/89

Earthquake: Central CA, SLO County

Southeastern Iran, Bam

Date: 12/22/03 12/26/03

Magnitude: 6.5 6.6

Depth: 7.6 km 10 km

Tectonic Setting:

Transform Convergent

Population: 239,000 100,000

Casualties: 2 >43,000

Injuries: 40 30,000

Damages: 40 buildings collapsed; small fires; power outages

60% of all buildings destroyed

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Fire: Ruptured gas lines ignite; 1994 Northridge earthquake. San Francisco burning after the 1906 earthquake.

Reducing Earthquake Hazards?

• Locate active faults

• Map high risk areas

• Better land-use planning

• Better building codes

• Better prediction both on land and in the worlds oceans.

• Improved global seismic sea wave warning system

Tsunamis

• Seismic Sea Waves– Triggers

– Speed, height, period, wavelength

– Trough often arrives first

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Fig. 10-20, p. 321

225,000+ ? - Indian Ocean earthquake with tsunami 12/26/ 2004100,000 - 1755 Lisbon earthquake, tsunami, earthquake and fire, Portugal and Morocco100,000 - Awa, Japan, 170370,000 - Messina, Italy, earthquake and tsunami, 190840,000 - South China Sea, 1782, including deaths in Taiwan36,000 - Krakatoa volcano explosion, 188330,000 - Tokaido-Nankaido, Japan, 170727,000 - Japan, 182625,674 - Chile, 186822,070 - Sanriku, Japan, 189615,698 – Japan, 3/11/11 (~5,000 missing)15,030 - Southwest Kyushu, Japan, 179213,486 - Ryukyu Trench, 17715,233 - Tokaido-Kashima, Japan, 17035,000 - Nankaido, Japan, 16055,000 - Moro Gulf, Philippines, 19763,000 - Papua New Guinea, 19983,008 - Sanriku, Japan, 19332,000 - Chilean Earthquake, deaths in Chile, U.S. (Hawaii), Philipines and Japan 1960165 - Aleutian Island earthquake, deaths in Hawaii and Alaska, U.S., 1946122 - Good Friday Earthquake, Alaska and Hawaii, U.S., 1964

Historical Tsunami Events and Resulting Fatalities

9.0 Magnitude Sumatran Earthquake Dec. 26, 2004

• Plates-Boundary Type: Convergent

• Depth: 30km

• Rupture Length and shaking duration: 1200 -- 1300 km,

3- 4 minutes

• Displacement: lateral ~20m, vertical 2-5m

• Energy Released: ~475 megatons of TNT or 23,000 A-Bombs

Banda Aceh, Sumatra Indonesia, 6/23/04

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Banda Aceh, Sumatra Indonesia, 12/28/04

Seacliff State Beach, Aptos, CA

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Capitola Ca

Pleasure Point, California Santa Cruz Yacht Harbor, California

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• Tsunami Hits Sana Cruz Harbor_NW side• Cowells Time Laps• Surge looking east, upper harbor. 2:37• U-Dock Floats Away• Trough hits Morro Bay• Kona Harbor Hawai time-laps • Earthquake in Japan_Liquifaction• Cars and ships washed away in Japan• Whirlpool in Japan• Major flooding in Japan / unique footage 2:14_Excellent• Another Overview_Starts with offshore waves_Excellent

• Tsunami moves across Pacific / Overview_• Japan Earthquake_Whirlpool ~1:00• Japanese-coast-guard-ship-hitting-tsunami-wave-head-on• Tsunami hits Town, 55 sec• Jim Berkland Seismic Warning for March 2011

Reducing Tsunami Hazards?

• Warning system in all major oceans• Better Land Use Planning• Local gov’t evacuation routes and

procedures• Education about warning signs

– Ground-shaking in coastal areas– Unusual disturbance of ocean, drop in SL– Move to high ground (several hours-days)– First wave generally not largest

Mass Movement

• Slumps / Slides• Mudflows, Earthflows• Rock Falls • Lahars (volcanic)• Debris Flows• Avalanchehttp://daveslandslideblog.blogspot.com/2008/

08/la-conchita-landslide-verdict.html

http://pubs.usgs.gov/fs/2004/3072/fs-2004-3072.html

Southern Italy Landslide 2/16/10La Conchita 1995

120 m wide, 330 m long, and >30 m deep, with an estimated volume of 1.3 million cubic meters.

Main Causes: Water, Seismic Activity,Volcanoes, Humans:

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La Conchita 1/10/05

Mass MovementTriggered by human activities

• Irrigation • Water leakage: septic

tanks other utilities• Surface water

diversion• Road construction• Mining operations • Logging• Fires• Excavation of slope

• SOLUTIONS?

Mass MovementSanta Cruz Mountains especially susceptible

• Topography• Geology (Dip Slopes)

• Rocks:

– soft

– fractured, folded, faulted

• Rainfall, El Niño winters

• Earthquakes

• Wildfires

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Mudslides in San Bernadino Mountains Dec. 2003

Earthquake events10/17/89

2/17/06 Philippines Landslide

• Mountainous region with history of landslides

• Up to 50% of forests logged in the past 30 years--not enough replanting

• Logging ban adopted 10 years ago not enforced

• Town put on geologic hazard map in May 2005

• 2 days of heavy rain + Mag 2.6 earthquake

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St. Bernard Township, Guinsaugon Philippines buried by mud 2/17/06

1,126 fatalities

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Volcanoes

• Volcanoes: landforms created when magma escapes from Earth’s interior through vents or fissures @ Earth’s surface and becomes lava. Lava cools and solidifies around vents forming volcanic rock.

• Globally, ~50 volcanoes erupt each year.

• Located at both convergent and divergent plate boundaries (not transform) and interior plate hot spots.

VolcanismHazards Benefits

• Volcanic materials burry and destroy habitats and property; toxic gases (acid rain)

• Ash clouds can block sun and lower global temperature

• Lahars (volcanic mudflows formed from sudden ice melting)

• Tsunamis

• Release of gases and water vapor forming atmosphere and hydrosphere

• Addition of fertile soils

• Addition of “real estate” (Hawaii, Pacific Islands, Iceland)

• Geothermal energy

• Info about Earth’s interior

Reducing Volcanic Hazards?

• Map high risk areas

• Volcanic zoning (no development in volcanically prone areas)

• Better prediction (monitor volcano’s surface, temperature, gas release, seismic activity)

• Effective evacuation plans

• Successful case histories: Mount Pinatubo Philippians, Mount St Helens, Oregon

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Coastal Erosion / Flooding / Rising Sea Level

• Storms

• Waves

• Coastal slides

• Human activities

Sea Level Measurements from San Francisco 1900 - 1999

Hurricane Katrina8/28/05

Vertical cross-section of New Orleans, showing maximum levee height of 23 feet (7 m).

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Human impacts on coastal erosion: Santa Cruz Harbor example

californiacoastline.org

Coastal Armoring; seawalls, rip-rap, and more

californiacoastline.org

Coastal Armoring; seawalls, rip rap and more

californiacoastline.org

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Reducing Coastal Erosion Hazards

• How will sea level rise impact coastal erosion?

• Establish better land-use planning

• Monitor erosion rates

• Map high risk areas

• Limit coastal armoring and damming of rivers

• Evaluate and monitor coastal engineering projects

Better land use planning

californiacoastline.org

Geologic Processes create:Hazards and Resources

– Hazards (dangerous events and conditions)

– Resources (the materials we use to get the things we want: fuel our cars, power our homes, computers, construct homes, buildings, roads etc.)

• Links between internal and external geologic processes:– internal processes create new

crust, cause hazards, concentrate minerals.

– external processes carve up crust creating landforms and environments which are subjected to hazards (flooding, landslides), concentrate minerals.