Natural Disasters

1. Natural Disasters Major Concept: Earth is a dynamic planet How do physical events in the environment affect our health

2. Although we cannot prevent most natural disasters, there are steps that scientists, engineers, governments, and citizens can take to resist damage and deal with the aftermath. A landslide caused by the Great Sichuan Earthquake in Sichuan Province, China

3. Earthquakes • Earth’s crust is broken into large pieces called tectonic plates, which float on a layer of molten rock. • The plates move in different directions • Earthquakes tend to occur along active plate boundaries. • Earthquakes can damage structures and trigger landslides and tsunamis.

4. Plate Tectonics Plates move at the rate of a few centimeters per year – about the same rate as your fingernails grow.

5. Asthenosphere convection currents cause the continental plates to move

6. Plate Tectonics There are three types of plate boundaries.

7. Convergent Plate Boundaries This is when the plates collide

8. Divergent Plate Boundaries This is when the plates separate

9. Transform Boundary When plates slide by each other

10. California’s San Andreas Fault is a Transform Boundary

11. San Andreas Fault The Pacific Plate (left) west side moves north The North American Plate (right) east side moves south WEST EAST

12. Oceanic - Oceanic Convergence

13. Continent - Continent Convergence A continent-continent collision is like a train wreck - both sides end up taking severe damage. Neither side wants to subduct. The entire Alpine-Himalayan mountain system from Spain to Thailand is behaving this way.

14. Seismograph

15. The 1994 Northridge Earthquake The last major earthquake in Southern California occurred almost twenty years ago

16. Big quakes release more energy

17. Earthquakes are found along plate boundaries

18. Volcanoes • Openings in Earth’s crust that eject molten lava and other materials • Ash and gases from volcanic eruptions can block sunlight, causing temperatures to drop. • Eruptions can trigger landslides and mudflows. • Molten lava can cover and destroy surrounding land. Did You Know?In 1991, Mount Pinatubo erupted in the Philippines, covering the area around the volcano with a layer of volcanic materials up to 180 m (600 ft) thick.

19. Volcanoes Most of the Earth’s active volcanoes on land are located around the Pacific Rim

20. “Hot Spots”Hawaii and Yellowstone

21. Storms • A storm is a violent disturbance in the atmosphere • 4 major types of storms: • Thunderstorms • Tornadoes • Hurricanes • Winter Storms • A meteorologist is ascientist who studies weather and tries to predict it

22. Storms • Tornadoes: Rotating funnels of air that can travel over 400 km (250 mi) per hr • Hurricanes: Storms that form over tropical oceans, with winds over 119 km(74 mi) per hour • Thunderstorms: Produce lightning and thunder, usually with heavy rain Did You Know?Hurricane Katrina, which struck New Orleans in 2005, caused more than $80 billion in damage and killed 1800 people.

23. Thunderstorms • A thunderstorm is a small storm often accompanied by heavy precipitation and frequent thunder and lightning. • Form in large cumulonimbus clouds (also called thunderheads) on hot, humid afternoons

24. Thunderstorms • Warm, humid air rises rapidly and the air cools, forming dense thunderhead clouds • Heavy rain falls, sometimes along with hail • Within the thunderhead cloud there are strong updrafts and downdrafts

25. Thunderstorms • Lightning heats the air to 30,000oC • Thunder is the sound of the rapidly heated air expanding suddenly and explosively • Light travels faster than sound so you see lightning before you hear thunder

26. Lightning • Lightning is a sudden spark, or electrical discharge • Positive and negative charges jump between parts of a cloud, or between nearby clouds, or between a cloud and the ground

27. Calculating Lightning Distances • Watch the sky for a flash of lightning. • Count the number of seconds until you hear thunder. • Divide the number of seconds by 5 to calculate the distance the storm is away from your location in miles (or divide by 3 for kilometers).

28. Tornadoes • A tornado is a rapidly whirling, funnel-shaped cloud that reaches down from a storm cloud to touch Earth’s surface

29. Tornado Formation • Warm, moist air flows in at the bottom of a cumulonimbus cloud and moves upward • A low pressure area forms inside the cloud • Warm air rotates as it meets winds blowing in different directions at different altitudes

30. Tornado Alley is an area of the United States that has a high frequency of tornadoes because cold, dry air moves south from Canada to meet warm, humid air from the Gulf of Mexico • 5 states that cross Tornado Alley are: • Texas • Oklahoma • Kansas • Nebraska • Iowa

31. The Fujita Tornado Damage Scale • Tornadoes are ranked on the Fujita scale by the amount of damage they cause

32. Tornado Safety • A tornado watch is an announcement that tornadoes are possible in your area. Stay tuned to the radio or television news. • A tornado warning is an announcement that a tornado has been sighted. Take shelter immediately! • The safest place to be during a tornado is in a storm shelter or the basement of a well-built building

33. Hurricanes • A hurricane is a tropical cyclone that has winds of 119 km/h or higher • Hurricanes form in the Atlantic, Pacific, and Indian Oceans • In the western Pacific Ocean, hurricanes are called typhoons • A hurricane begins over warm ocean water as a low-pressure area, or tropical disturbance. • A hurricane draws its energy from the warm, humid air at the ocean’s surface • As the air rises and forms clouds, more air is drawn into the system • Inside the storm are bands of very high winds and heavy rains • Winds spiral inward toward the area of lowest pressure at the center

34. Hurricane Formation

35. Hurricanes • Hurricanes last longer than other storms, usually a week or more • After a hurricane passes over land, it no longer has warm, moist air to draw energy from so it loses strength • A storm surge is a “dome” of water that sweeps across the coast where a hurricane lands • For safety during a hurricane, people are told to evacuate • Evacuate means to leave the area immediately

36. Winter Storms • All year round, most precipitation begins in clouds as snow • A large amount of humid air that cools below 0oC can produce a winter storm • Blizzard = Blowing snow and reduced visibility • Main Hazards • Vehicle accidents • Hypothermia • Exertion • Immobility

37. Avalanches • Masses of snow that slide down a slope • Conditions favoring avalanches: • Slope greater than 30 degrees • Unstable snowpack • Heavy snowfall • Warm temperatures Did You Know?A big North American avalanche can contain 230,000 m3 of snow—about the equivalent of 20 football fields filled with snow 3 m (10 ft) deep.

38. Impacts • Main direct impacts are deaths, injuries, and economic losses to communities affected. • Indirect impacts include wider economic losses to tourism industry, transport delays, and wider spatial economic losses.

39. Contributing factors • Heavy rainfall on snow (more likely in Scotland than the Alps!) • Deforestation - reducing slope stability • Vibrations – skiersor more dangerous earth movements • Long cold winters then heavy snow falls in spring. i.e. slip plane created.

40. Snow-pack Stress • Snow lying on a slope is subject to stress : • gravity is pulling it downwards • adhesion and weight is keeping it “stuck” to the slope. • Often these stresses are delicately balanced, and a slight change can bring about failure, particularly where the snow-pack is under tension.

41. Powder snow avalanches • No warning. • Up to 200mph • Up to 50 tons/m 2 force • Occur at any time in season. • Example :Galtur, Austria.

42. Wet snow avalanches • Usually late in season. • Slow moving (5-15mph). • Considerable weight of wet snow (up a million tonnes). • Example : Odda, Norway.

43. Slab avalanches • Slab avalanches are most common occurrence. • Often started by human error. • Most frequent cause of death amongst skiers, snowboarders, and power-skiers. • Speeds up to 100mph.