Movie worksheet: volcano 1997

cooling wilshire boulevard

after viewing scenes from volcano, you might have asked, "could water be used to stop lava from flowing? if so, how much would it take? "

here’s the situation: a basaltic volcano erupts in the heart of los angeles. lava pours down the streets, destroying buildings, starting fires, and causing general chaos. tommy lee jones organizes firefighters, public works employees, residents, and national guard helicopters to stop the lava flow. they do this in a matter of minutes by blocking the flow first with concrete traffic barriers, and then chilling it with water pumped by fire hoses and dropped from helicopters.

is this possible?

actually, we can figure this out.

the width of the street - building to building – is about 30 m across (~100 ft), and we want to cool and solidify the lava front – say about 150 m (~500 ft) down wilshire blvd. we want to solidify it to about a depth of 1 meter (a good solid crust about 3 ft thick). so we have a surface area of 4,500 m2 (length times width), and 1 meter thick gives a total volume of 4,500 m3 of lava to solidify.

download the excel spreadsheet "lavacooling. xls" in order to complete the assignment or you may complete the assignment on the hard copy on the next page.

you will also need two pieces of information:

total energy needed to cool the lava (term a in spreadsheet) = 8.78 x 1012 joules

total energy to heat and boil water (term b) = 2.64 x 106 joules/kg

cooling a lava flow on wilshire blvd., los angeles

useful information

carrying capacity of a helicopter: 500 gallons of water

number of helicopters: 20

pumping rate of 1 fire truck (if water supplied from city water main via fire hydrants): 1500 gallons/min

number of fire trucks: 20

worksheet

total energy needed to cool lava a joules

total energy to heat and boil water per kilogram b joules/kg

kilograms of water needed = a / b c kg

1 gallon of water (3.8 liters) weighs 3.8 kilograms

number of gallons of water needed = c / 3.8 d gallons of water total

final answers

no. helicopter dumps = d / helicopter capacity e dumps

no. trips per helicopter = e / number of helicopters trips

gallons per minute for 20 fire trucks f gallons/min

minutes of pumping for 20 fire trucks = d / f minutes of pumping