GEOL 0820
Natural Disasters
Spring, 2025
LECTURE #2: Energy Sources for Disasters
Date:13 January 2025
I.Review from last class
● syllabus/website details
O website: http://ivis.eps.pitt.edu/courses/geol0820/
contains all information about the class,course notes,etc.
notes typically go online the morning of that day's lecture
● introduction to the topic of natural disasters
o be sure to review the notes if you missed the first class
II.This week
● the link to the first video homework is active
o please make time to watch and take notes
● Recitations start this week (tomorrow)
o please make sure you attend the class and talk with your TA about what is expected because this is a large percentage of your grade!
· make sure that you have your copy of the recitation manual (it is now in the
Pitt Bookstore (https://pitt.verbacompare.com/comparison?id=4701496 ) you will need this for the first recitation in order to complete the work
Ⅲ.Energy Sources for Disasters
1.external heat (Sun)
2.internal heat (Earth)
3.force of gravity
● external heat
o solar energy
■ drives atmospheric motions
hurricanes,tornadoes,etc.
heat flow from the sun is 5300 times more than from the Earth's interior
very small fraction of solar output reaches the Earth's surface
of that,25%goes into evaporation of water
drives atmospheric circulation
gives rise to large storms
■ wavlc(g)related to the frequency (and the energy!)
v=frequency(Hz or cycles/sec)
o what is solar flux?
■ amount of energy over a given area (W/m²)
■ measured perpendicular to incoming energy
there's a different flux at the equator than the poles
different flux in Pittsburgh in the winter vs.the summer
● internal heat
o from the planet's formation
■ lower density materials like rocks,gases,water,radioactive minerals rose
■ higher density materials like metals sank
■ when the internal heat of the Earth>1000℃(~1800°F)iron melted and the liquid sank toward the core (gravity)
released potential energy
increased the temperature even more!
enough to melt rocks and begin the process of differentiation of the Earth's layers (core,mantle,crust)→we will examine this more in the coming weeks
o from impacts of comets and asteroids early in the Earth's history
■ tremendous amount of heat created and stored
transfer of potential energy→kinetic energy→frictional heating
Potential Energy(PE)=m gh
Kinetic Energy (KE)=1/2 mv²
where,
m=mass of the object;g=gravitational constant
h=height/distance traveled;and v=velocity of the object
so,how would you solve for the velocity of an object?
work out your solution here before lecture:
o from continued decay of radioactive elements
■ this heat drives plate tectonic motions
earthquakes,volcanoes,etc.
O radioactive minerals
Potassium-40,Uranium-238,Thorium-232,many others...
■ releasing neutrons,protons or particles from the atom's nucleus changing the atomic number/isotope and therefore the element the particle released is converted into energy
heat the surrounding rocks
damage/kill living tissue
Potassium-40(19p+21n)→Agron-40(18p+22n)
■ half-life:
time required for 12 the number of atoms of the parent element to decay into the daughter element
Parent
Aluminum-26 Uranium-235 Potassium-40 Uranium-238 Thorium-232 Rubidium-87 Samarium-147
Daughter
Magnesium-26 Lead-207
Argon-40
Lead-206
Lead-208
Strontium-87
Neodymium-147
Half Life
720,000 0.71 billion 1.3 billion 4.5 billion 14 billion
47 billion
106 billion
Copright O The MeGraw Comparies,ine.Pamission requred tor rmproductio
Increasing Time Measured in Half-Lives
age of the Earth
--4.57 billion years
--measuring radioactive elements in lunar rocks
--how can moon rocks tell us the age of the Earth??