Hazardous Environments Flashcards
Body Waves
Bodywaves: waves within the earth’s interior
P waves: travel by compression and expansion
S waves: travel with a side to side motion
Surface Waves:
Surface waves: when body waves reach the surface:
Long waves: sideways movement
Rayleigh waves: up and down movement - most hazardous.
Soil liquefaction
loose sand and silt that is saturated with water can behave like a liquid when shaken. Pore water pressure increases so sand grains lose contact with each other = soil loses ability to support structures. = quickly solidifies hence structures trapped in the ground.
E.g Christchurch Earthquake aftershock of 7.1 in 2011 caused widespread liquefaction. Leading to $16bn in damage.
What and causes of Tohoku earthquake
11 March 2011 earthquake and Tsunami, Japan.
Magnitude 9, lasted 6 minutes.
Tsunami waves, on average 3-6m.
Causes:
Pacific plate subducting beneath the Eurasian plate. Focus 32 km in NW Pacific ocean. Epicentre 70 km east of Tohoku. Earthquake caused an upthrust of 8m along 180 km seabed.
Impacts of Tohku earthquake
Primary:
16,000 deaths in Japan. Estimated 92% died from drowning, 4% crushed in earthquake. 127,000 buildings destroyed.
Secondary:
Fukushima nuclear incident. 4.4 million households without electricity, 1mn households without access to water. 25 million tonnes of debris in coastal areas.
World bank estimated economic cost = US$235bn.
Management before Tohuko earthquake
Many large foreshocks record: e.g first major fore shock = 7.2 magnitude on 9th march.
Recurrence interval for tsunamis on sendai plain estimates a 800 - 1100 year recurrence interval for large tsunamigenic earthquakes. = In 2007, the probability of an earthquake with a magnitude of 8.1–8.3 was estimated as 99% within the following 30 years
One minute before the earthquake was felt in Tokyo, the Earthquake Early Warning system, which includes more than 1,000 seismometers in Japan, sent out warnings of impending strong shaking to millions = saved lives as high speed trains and factory lines stopped, earthquake drills enacted.
Earthquake proof design; e.g Mori Tower, Tokyo. - 54 stories but has 192 of fluid-filled shock absorbers filled oil, which acts as a counter balance to swaying.
Tsunami wall line 40% of Japan’s coast - but these were overtopped. E.g at miyako 4m in height. Replaced by 12.5m
management after Tohoku earthquake
Residents within 20km of Fukushima were evacuated after the failing of the cooling system = radiation levels inside 1000x normal =
State of Emergency Declared.
Japanese red cross reporting $1bn in donations, 116 countries and 28 NGOs offered assistance.
What and causes of haiti earthquake
12 January 2010 Haiti Earthquake. Magnitude 7.
Focus 13 km. Epicentre 25 km west of Port au Prince. Occurred along a conservative plate boundary. Caribbean plate is moving 20mm per year faster than the North American Plate. g
impacts of haiti earthquake
160,000 deaths. 250,000 buildings severely damaged/destroyed. (there are no building codes in haiti)
management after haiti earthquake
More than 20 countries sent military personnel to assist with relief and rescue. But efforts were restricted due to congestion and blocked roads. 23 NGOs raised US$1bn for relief. Six Months after the quake, 98% of rubble remained uncleared.
Icelandic eruption
Icelandic eruption: persistent fissure eruption. Large quantities of basaltic lava build up vast horizontal plains.
hawaiian Erruption
Hawaiian Eruption: runny basaltic lava travels down the sides of the volcano in lava flows. gases escape easily. Occasional pyroclastic activity but small.
Strombolian eruption
Strombolian Eruption: frequent gas explosions which blast fragments of runny lava into the air to form cones. Very explosive eruptions with large quantities of pyroclastic rock thrown out. Common to have white steam cloud from crater.
Vulcanian eruption
Vulcanian eruption: violent gas explosions blast out plugs of sticky lava. Fragments build up into cones of ash and pumice. Occur when there is very viscous lava which solidifies rapidly. Often large quantities of volcanic ash.
Vesuvian eruption
vesuvian eruptions: very powerful blasts of gas pushing ash clouds high into the sky. lava flows and ash clouds.
Plinian eruption
Plinian eruption: gas rushes up through sticky lava and blasts ash and fragments into the sky in the largest and most violent eruption. Immense clouds of gas and volcanic debris kms thick.
Pyroclastic flows
flow of hot gas, ash and larger volcanic matter. Reaches up to 700C and 150km per hour.
Mount St Helens What and Causes
18th May 1980 VEI 5 eruption at Mount St Helens, Washington.
Volcanoes formed due to the subduction of the Juan da Fuca plate beneath the North American Plate forming the Cascade volcanic chain.
A 5 magnitude earthquake on May 18, 1980, caused the entire weakened north face to slide away, creating the largest landslide ever recorded. This allowed the partly molten, high-pressure gas- and steam-rich rock in the volcano to suddenly explode northwards.
Mount st Helens impacts
primary:
Eruption column rose 80,000 feet in the air = deposited ash in 11 states, 65% silicon dioxide.
Snow, ice and glaciers on volcano melted = lahars that travelled 80 km SW and affected 3 out of 4 major drainage systems.
Pyroclastic flows formed travelled at max speed of 1,080km/hour. Destroyed 600km2 of forest but extreme heat caused tree deaths beyond this zone.
57 deaths from asphyxiation some fro burns. Due to pyroclastic flow that was 360 C when it hit people and filled with gas and debris.
200 homes, 47 bridges, 15 miles of railways, 185 miles of roads destroyed.
Secondary:
Ash deposited in 11 states = fall in visibility= closure of interstate 90 for 1 week. 1000 flights cancelled.
$3bn dollars of damage.
Mount St Helens management
before:
123 years of dormancy. Forecasting before event due to two month series of earthquakes and steam venting episodes . 8 earthquakes per day the week before the eruption. The mountain swelled with magma and bulged outwards at a rate of 1.5m per day.
Washington state Governor placed a 5 mile red zone around the summit. BUT the blast extended to 4x the exclusion zone/
after:
removing the ash from one town took 10 weeks and cost £1million.
Fall example
E.g Yosemite National Park January 2017, Rockfall with total volume of this slide was about 20,000 cubic meters
Slides example
E.g Southern Leyte Mudslide, Philippines 2006. 1126 deaths
Heave example
E.g terracettes visible at manger, near uffington white horse.
Avalanche example
E.g Huascaran avalanche, peru may 1970: 80 million cubic feet of ice, mud and rock travelled nearly 11 miles, burying the towns of Yungay and Ranrahirca in up to 300 feet of rock and debris.
What are hurricanes?
A severe, rotating tropical storm with heavy rains and cyclonic winds exceeding 74 miles per hour. An area of low pressure (as low as 880mb) over tropical or subtropical water where trade winds converge.
Surface winds of 74 mph. Anti clockwise rotation in N Hemisphere.
Where do hurricanes occur
Over oceans (5-20 N or S of the equator), although some make landfall.
They are NOT on the equator;
They tend do occur on east coasts.
They are NOT found in South America.
how do hurricanes form?
Warm oceans (at least 26C) between the tropics, heats the air above it = expands = less dense = rapidly rises = extreme low pressure area at surface (880mb)
Also warm oceans = evaporation = condensation of water vapour when cools = latent heat released which drives the storm as air rises further and more rapidly = creating lower pressure at surface
Unstable conditions; atmosphere cools quickly with height that a parcel of rising air is warmer than air at the same height so continues to rise.
There is low wind shear; winds in the upper troposphere must no be too strong to remove the top of the storm system.
Spiralling system due to coriolis force.
Hurricane Irma what?
Hurricane. Formed 30 August 2017 near Cape Verde Islands. Made landfall on 6th September in Barbuda,
(282kph wind speeds) continued north as a Cat 5 hurricane. Reached Florida on 10th September as Cat 4 (209kph) Dissipated 13 September 2017. Diameter of 644km.
hurricane irma impacts of USA
Primary:
92 deaths in the USA. 50% from drowning.Greatest impact in florida.
Peaks of 550mm rain in Florida.
Secondary:
Damage in the USA was estimated at $50billion. 73% of Florida was left without electricity.
Havy rain and storm surges caused 32 rivers to overflow.
Hurricane irma management USA
Before:
In Florida, in 2002, legislature passed a statewide building code that requires buildings to at least be able to withstand winds of up to 111 mph. E.g with multiple construction tiw from the walls to floor, and reinforced windows with impact glass.
10-mile-long seawall in Galveston, Texas
after:
More than 40,000 federal personnel, including 2,650 FEMA staff, were in place by September 14. In addition, FEMA had transferred 6.6 million meals and 4.7 million liters of water to states in the Southeast after Irma as of the 14th
hurricane irma impacts of caribbean
42 Deaths in Caribbean islands. (10 in cuba, 11 in French West Indies)
Flattened 95% of buildings in barbuda. Island uninhabitable to 1600 residents. Economic loss for Antigua and Barbuda estimated at $120mn.
Waves of 9m reached Puerto Rico. 1mn residents lost power.
hurricane irma management in caribbean
Hurricane Warnings were issued for the northern Leeward Islands, Puerto Rico, and parts of Hispaniola on September 5.
In Turks and Caicos island Officials spread warnings to residents in English, Creole, and Spanish via social media, radio, SMS text, and WhatsApp.
11, 200 people were evacuated from the dominican republic.
Preparation in Haiti was poor, with no mandatory evacuation orders.
In the Bahamas the government secured sport facilities to use as shelters, evacualted 1,600 people by air form southern islands, cut power supply.
What are tornadoes, where do they form.
What are Tornadoes?
A rapidly rotating column of air between the base of a cumulonimbus cloud and the earth’s surface.
Typically 20-100m wide, track of 1 mile, lasting for no more than 20 minutes.
Where?
Overland. 90% in the USA in Tornado Alley. (Where cold air form the rocky mountains meets warm air form the gulf of Mexico in Central and Southern States).BUT rare; 1200 in USA a year.
Indiana/kentuckey tornado
indiana/kentucky tornado november 2005 = killed 16 people, injured 200, 1.2km wide and track of 32km. Emergency sirens sounded as warnings but most did not responds as tornado occured at night. But can also occur in other areas
Birmigham tornado
E.g birmingham in July 2005 = winds of 209 km/h tore through small heath district, 1000 buildings damaged, 12 injured. Government granted emergency aid to birmingham. Leaflets on practical advice were issued after event.
How do tornaodoes form
Extreme heat on the ground causes warm, moist air to rise in updraughts, as it expands and becomes less dense.
This meets cold dry air, creating unstable conditions and forming cumulonimbus clouds.
The upward movement of air is rapid, creating low pressure at the surface = winds are drawn in from different directions causing rotation.
Wind speed increases with height, causing higher, faster moving air to roll over slower moving air below.
This creates a horizontal spinning column of air, that is known as a vortex. This turns vertical due to horizontal updraughts of warm rising air.
This is known as a supercell, as a thunderstorm has a persistent rotating updraught at its core.
Downdraughts of cooler air, due to xxxxx within the supercell force the column down. If the column touches the earth’s surface it is classified as a tornado.
Tornaodes hazardous impact facts
On average tornadoes kill 60 people per year.
the strongest winds on the face of the planet. On average 70 mph, but reaching 300 mph.
BUT tornadoes tend to cause less than 1/10th of the economic damage of hurricanes per year, because hurricanes affect a much large area for a longer time period.
