Learn: Natural Disasters Exam 2 University of Iowa

Shield Volcanoes

Low viscosity, very wide

Strato (Composite) Volcanoes

High viscosity, steep, most dangerous

Cinder Cone Volcanoes

Steep, but steady, gentle eruption

Where are volcanoes found?

Plate boundaries

What boundary type does the Ring of Fire have?

Convergent

What is a lahar?

Volcanic mudslide

How to melt things:

Increase temperature, decrease pressure, increase H2O

Why do volcanoes happen?

Magma comes to the surface and new crust is being generated

What are hazards of volcanoes?

Lava, pyroclastic flows/surges, ash clouds, fallout, lahars/ debris avalanches, gases

Viscosity

The ability of a substance to resist flow

Categories of explosive volcanoes

Hawaiian

Strombolian

Vulcanian

Plinian

Ultraplinian

Tambora, Indonesia

Supervolcano

Greatest historic eruption: VEI 7

Lost 1450 m (4700 ft) of elevation

80-90,000 dead

Tropical cyclone names

Tropical Depression

Tropical Storm

Hurricane (N Atlantic, E Pacific)

Typhoon (W Pacific)

Cyclone (Indian Ocean, S Pacific)

Cyclonic rotation

Northern Hemisphere: Cyclones circulate counter-clockwise

Southern Hemisphere: Cyclones circulate clockwise

What do you need to form a cyclonic storm?

Warm ocean water

Cold air & high P-loft

>5 degrees latitude

Most destructive side of the surge

The side parallel to storm

Rainbands (how hurricanes forms)

Bands of (thunderstorms) spiraling around and towards storms center

Wrap around eye wall

Can produce heavy bursts of rain

Also can have tornadoes

How do hurricanes die?

-Moves over cold water

-Stays stationary

-Moves over land

-Low p-aloft

Hurricane hazards

• Storm surge

• High winds

• Flooding and landslides

• Ocean waves

• Inland tornadoes

• Flying debris

Deadliest storm in the world

Cyclone Bhola

Nov 12th, 1970- Bangladesh

Cat 3 storm with 9m storm surge (30 ft)

Killed 300,000 to 500,000 in the Bay of Bengal

Know the names and nature of the disasters caused by the three major hurricanes that hit the USA in 2017

Hurricane Maria

Hurricane Irma

Hurricane Harvey

Why was Hurricane Mitch so deadly in Nicaragua and Honduras?

It dumped rain and created a lot of landslides

How high can winds be in a tropical cyclone? What are the other hazards associated with these storms?

-Sustained winds as much as 215 mph

-Intense areas of rainfall and storm surge, possibly tornadoes

Know the different regional names for cyclonic storms. You should also know the classifications (i.e., what is bigger, a tropical depression or a tropical storm? How are these categories defined?).

Tropical Depression

Tropical Storm

Hurricane (N Atlantic, E Pacific)

Typhoon (W Pacific)

Cyclone (Indian Ocean, S Pacific)

Why do hurricanes rotate, and which way do they rotate in the different hemispheres?

Coriolis Effect: an imaginary force that appears to be extended on an object moving within a rotating system. In the northern hemisphere, cyclones circulate counterclockwise, In the southern hemisphere, they circulate clockwise.

What ingredients do we need for a hurricane to form? Because of these ingredients, where and when do hurricanes form?

Warm ocean water

Cold air & high P-loft

>5 degrees latitude

How do most hurricanes start (what generates the initial disturbances that build into these storms)?

Release of heat during condensation causes air to expand and rise. The removal of air reduces pressure at surface.

Why do we see a lot of hurricanes forming in association with ITCZ, and what is the ITCZ?

(Intertropical Convergence Zone)

Convergence of air at the end of a mid-latitude _______ boundary in the area near the Gulf of Mexico

Easterly _____, tropical disturbances from N. Africa near ____. Converging winds on east side of wave are associated with thunderstorm development. 60% of all storms, and most big Atlantic hurricanes

Why do we need warm ocean surface water for hurricanes to form, and how deep does this water need to be?

The warm, moist air over the ocean rises upward from near the surface. Because this air moves up and away from the surface, there is less air left near the surface. Another way to say the same thing is that the warm air rises, causing an area of lower air pressure below.

-At least 250 ft deep

Why does wind shear matter to hurricanes (if we have high wind shear, what will happen to a developing hurricane)?

It controls the speed and direction of the hurricane, high wind shear causes the hurricane to be stronger

Know hurricane anatomy and where winds are the strongest and weakest. What would it be like to be in the eye of a hurricane vs. standing in the eye wall (which would be a better place to stand)?

Being in the eye wall would be the most deadly. The eye is the calmest part of the hurricane.

Where are rains generally more intense in tropical cyclones?

Eye

How does eye diameter relate to hurricane wind speeds?

Smaller eye = higher wind velocity

What causes tropical cyclones to intensify and weaken?

Weaken: Moves over cold water, stays stationary, moves over land, low p-aloft. Intensify: Strong vertical winds

What is the Saffir-Simpson Hurricane Scale based on?

Pressure, wind speed, storm surge, damage level

Which side of a hurricane is most destructive, and why?

Most destructive side (wind and storm surge) is the one parallel to storm forward motion

How do we name hurricanes (what does the list for each year look like, how many lists are there, and why do we pull names occasionally from lists)?

6 lists of 21 names used in rotation (no Q, U, X, Y, Z names) We take names out when the storm is too deadly or costly

What year had the most Atlantic hurricanes and how many did we have?

2005- 28 hurricanes

What are the different hazards associated with hurricanes?

• Storm surge

• High winds

• Flooding and landslides

• Ocean waves

• Inland tornadoes

• Flying debris

What was the tallest ocean wave height ever measured?

62 ft

What was so special about Hurricane Patricia?

Strongest hurricane ever recorded in the Western Hemisphere and broke the record for lowest pressure

What was the most deadly hurricane on record, and why was it so deadly?

Hurricane Galveston

What has been the effect of climate change on hurricane frequency and intensity?

Waters are getting warmer and that causes an increase in the frequency and intensity of the storms

What earth process causes volcanism?

Plate tectonics

Two locations were discussed that are significantly imperiled by volcanoes? What are these locations and which volcanoes pose hazards for these locations?

Nevado del Ruiz

-Armero built on 1845 lahar deposits

-November 13th, 1985: a year of minor earthquakes

-Second worst disaster

-20,000 people died from lahars

Mt Rainier

-Future catastrophe

-At least 50 major lahars over the past 10,000 years

What are the different volcanic hazards that we have discussed, and should also know whether their impacts are primarily manifested at a local vs. a global scale

Lava flows

Pyroclastic flows and surges

Ash Clouds

Fallout & ballistics

Lahars and debris avalanches

Volcanic gases

Local: suffocation and lung damage

Global: climate change

Be familiar with the specific examples of different particular volcanoes that we discussed (e.g., Nyiragongo, Mt. Vesuvius, etc.).

Nyiragongo

-Active stratovolcano

-Overlaps two older volcanoes, surrounded by smaller cinder cones

Mt. Vesuvius

-Formed as a result of the collision of two tectonic plates

-Eruption column 44 km high (144,000 ft)

-Lost 1450 m (4700 ft) of elevation

-80-90,000 dead in local area

How does pahoehoe lava differ from a'a lava? WHY do the two types of lava differ (what properties change)?

Pahoehoe: fluid, flowing ropy texture, forms when lava flows more slowly

A'a: clinkery, jagged blocks, less viscosity

What is viscosity a measure of, and what three factors interact to determine the viscosity of magmas/lavas?

Viscosity: The ability of a substance to resist flow

-Controlled by temperature, composition, gas content

-Shawty thicc

How does silica content modify viscosity, and why? Which type of magma would be more viscous, basaltic or rhyolitic magma, and why?

The higher the SiO2 content of magma, the more polymerized the melt is (increases the "internal friction" and the viscosity)

-Rhyolitic is more viscous

You should know the relative ranks, in terms of the VEI, of Hawaiian, Strombolian, Vulcanian, Plinian, and Ultra-Plinian eruptions.

Hawaiian

Strombolian

Vulcanian

Plinian

Ultraplinian

What type of eruption (from the above) is associated with fire fountains? How about bubble pops and short-term vigorous explosions? Pyroclastic flows?

Hawaiian- Fire fountains.

Strombolian-Bubble pops

Vulcanian- Short-term vigorous explosions

Plinian & Hawaiian- Pyroclastic flows

What is the VEI, and how does the volume of material and style of eruption erupted relate to VEI scores?

-Volcanic Explosivity Index

-It measures how much volcanic material is ejected, the height of the material thrown into the atmosphere, and how long the eruptions last

How does a pyroclastic flow differ from a pyroclastic surge, in terms of behavior? How do they rank in terms of deadliness?

Flow- lower gas content, greater amounts of particles, stays in valleys, less dense than water

Surge- higher gas content, can go over hills (flows close to the surface) more deadly

Know what happened at Mt. Pelee and St. Pierre.

Pelee- Volcano erupted and killed a whole town of 28,000 people(pyroclastic surge)

Pierre-cloud of burning ash filled through the city, nearby volcano erupted and killed more than 27,000 people

What are the different parts of an eruption column (anatomy)?

Gas and thrust

Convective thrust

Umbrella region"downward plume" and fallout

What is a debris avalanche? We discussed two volcanoes that had debris avalanches. Be able to name these volcanoes.

Sudden catastrophe collapse(landslide) from an unstable side of a volcano, many volcanoes cones are steep and unstable due to rapid growth of core

Ex: Nevado del Ruiz & Mt. Helen

Know the details about Tambora's big eruption-how did this impact climate globally? What were the effects on people living both nearby and far away?

Greatest historic eruption: April 5-11 1815, VEI 7

Est. 175 km3 of lava erupted (50 km3 without bubbles)

Eruption column 44 km high (144,000 ft)

Lost 1450 m (4700 ft) of elevation

80-90,000 dead in local area

Global Impact:

1816 - Famine in New England

1817- Famine in Germany

Ireland: 100,000 dead - mass exodus

Typhus- Bubonic plague & cholera epidemics

100,000 dead in SE Europe, Mediterranean, and India

What happened when Laki erupted?

The largest basaltic eruption in history, 8 months worth of lava flows, 333~14.7 km3 of basaltic lava that came out of 140 vents along a 23-km-long set of fissures and cones

You should know the sorts of gases that are released during volcanic eruptions, and their impacts.

Hydrogen sulfide and hydrochloric acid that can irritate eyes and respiratory systems, and carbon monoxide

What happened when the Deccan Traps were erupted? What major evolutionary event is it associated with? How could eruption of a volcanic province like this impact global climate and global ecosystems?

The eruption of the Deccan traps is associated with the Cretaceous-Tertiary extinction event, which killed the dinosaurs.

-This eruption would have released large amounts of greenhouse gases, leading to climate warming. -Other released gases would have contributed to ocean acidification, further disrupting the food chain.

What determines eruption style and type of volcano formed?

Style depends on viscosity, gas content, and (to a lesser extent) volume of erupted material.

Know the effects temperature, silica content, and water content have in the viscosity of magmas. How are these magma characteristics reflected in volcanic landforms, and how does this all relate to plate tectonic setting?

Effect of temperature - Higher ➡ lower viscosity

Effect of magma composition (SiO2) - Higher ➡ melt more polymerized, higher viscosity

Effect of water concentration in magma - Higher ➡ depolymerizes melt, lower viscosity

What are the three different ways by which we can generate melt? Which of these processes occurs at a mid ocean ridge? Which occurs within a mantle plume?

How to melt:

Increase temperature

Decrease pressure

Increase H20

Basaltic and andesitic- mantle

Rhyolitic-mid ocean ridge

How many coastal states are there in the United States, and what is the average rate of coastal erosion? What proportion of coastal homes (within 500 feet) do we anticipate could be lost to erosion in the next 60 years?

-30 coastal states in the United States. Average rate of coastal erosion is 2-3 ft/yr.

-1 in 4 homes

Where in the United States is coastal erosion highest?

Gulf of Mexico

How are wave energy and wave amplitude (height) related?

Wave energy depends on height squared

What is the rate of land loss in Louisiana, and why is Louisiana losing coastline so rapidly?

34 square miles of land- for the last 50 years. 1,900 square miles of land from 1932-2000, roughly the size of Delaware. Caused by oil and gas companies

What drove rapid land loss in Pacifica, California in the winter of 1997-1998? What were some of the different technologies and strategies that were implemented to try to slow/stop coastal erosion in these communities?

El Nino. Tried to build seawall in Jan 1998 but winter storms stranded machinery. Revetments kept boulders in place.

What trends do we see in sea level over the past several decades? What drives sea level rise (two mechanisms)?

-Heating of water and melting of glaciers

What three factors determine wave height?

Wind Duration

Wind Velocity

Fetch (distance over which wind blows)

What is significant wave height?

Average height of the highest 1/3 of the waves. Individual waves may be more than twice the significant wave height.

What controls the Earth's tides, and what are spring vs. neap tides? When do spring and neap tides occur?

-Earth's gravitational pull

-Neap tides are especially weak tides. They occur when the gravitational forces of the Moon and the Sun are perpendicular to one another. They occur during quarter moons.

-Spring tides occur just after a new or full moon, when there is the greatest difference between high and low water.

Know the difference between constructive and destructive interference in waves, and know which process would produce larger waves.

Constructive-interference is obtained by interference of in-phase waves

Destructive-interference is obtained by from out-of-phase waves

At what depth does a water wave start feeling the bottom? When does a wave break, and how do wave height, velocity, and wavelength change as waves approach shore?

-In general a wave will start to break when it reaches a water depth of 1.3 times the wave height.

-Wavelength & velocity decrease and wave height increases

What is wave refraction?

Wave refraction is when waves approach a straight shoreline at an angle.