Environmental Hazards
BRING:
Video: Asteroids, Deadly Impact
“Rock” samples – paper with parent and daughter percents
Graph paper
U238 parent daughter graph
2cmX8cm strips of paper
DISCLAIMER: These notes do NOT cover everything you need to know. You may need to look up some
item or concept online or in a text. Test questions are not exact copies of the OBJECTIVES but if you
know the OBJECTIVES thoroughly, you should do well on the exams.
Part 1 - Global Warming- rough notes
Part 2 – What killed the dinosaurs? – rough notes
Part 1 - Global Warming Rough Notes
Covered in class and notes on “Comparative Environments”
I will not ask you about this on Test 2.
BUT be sure to do the assignment GLOBAL WARMING
Points from this assignment COUNT TOWARD TEST 2.
Part 2 – What killed the dinosaurs? – rough notes
OBJECTIVES:
Define and differentiate between the following: atom, element, molecule, ion, isotope. (Look up these on
line or in your text.)
What is meant by radioactivity? For what do astronomers use radioactivity? What is meant by parent and
daughter in this context?
Define half-life. If you start with 100 grams of radioactive material, how much is left after one half-life?
After two half-lives? After three half-lives?
Given a graph of a parent-daughter decay, and given a “sample” with a known parent percent, find the age
of the “sample”
What evidence suggests that a meteor strike killed the dinosaurs? When?
CLASS:
Death of dinosaurs ~65 million years ago
Eras and mass extinctions from fossil records
Permian (~251 million years ago) - ~ 90% of species on Earth wiped out
Late Cretaceous (65 million years ago) – 70 % of species wiped out
Others
We will focus on the Late Cretaceous era.
Some terminology regarding eras:
Older sources define the era after the Cretaceous (symbol K) as the Tertiary (symbol T) era.
Newer sources define the era after the Cretaceous as the Paleocene era.
These notes use the older terminology.
Something happened to wipe out the dinosaurs and 70% of the species on Earth
Fossil record (Dinosaurs, ammonites)
How do we know the ages?
One way: Radioactive dating, half-life
See http://www.agiweb.org/news/evolution/datingfossilrecord.html for example.
Or http://www.astronomynotes.com/solfluf/s4.htm
Or http://phet.colorado.edu/en/simulation/radioactive-dating-game
Done in class - Exercise on half-life and reading parent-daughter decay graphs to find the age of a sample.
Sample parent-daughter graph
(Currently unable to find the source for this graph.)
Could volcanoes have wiped out the dinosaurs?
Examples – Pinatubo, St Helens, Deccan Traps
More likely a meteorite impact (Alvarez and company)
Or a combination of the two
Original Alvarez paper: http://adsabs.harvard.edu/abs/1980Sci...208.1095A
Nice summary at: http://science.jrank.org/pages/2643/Extinction-asteroid-impact-theory.html
Evidence for meteor impact
1. K-T layer or boundary
Thin, dark layer, world-wide, 65 million years ago
Dino fossils below, none above
70% of species on Earth died out
2. K-T layer is dark
3. Iridium in K-T layer
4. Shocked quartz in and near K-T boundary
5. Chixulub crater in Yucatan Peninsula in Mexico
http://www.jpl.nasa.gov/earth/features/chicxulub.cfm
Has Earth been whacked before?
Other craters http://liftoff.msfc.nasa.gov/academy/space/solarsystem/meteors/Craters.html
Other impacts – Example Chelyabinsk Feb 2013
Other collisions in solar system:
Jupiter impact (Comet Shoemaker-Levy 9 in 1993)
Chelyabinsk Feb 2013
Potential for future collisions
http://liftoff.msfc.nasa.gov/academy/space/solarsystem/meteors/ImpactHazard.html
See also video: “Asteroids: Deadly Impact” from National Geographic especially the part starting with
Gene Shoemaker through Tunguska.
Updates on what killed the dinosaurs
2012 Stronger argument for volcanoes as primary source
http://www.livescience.com/25324-volcanoes-killed-dinosaurs.html
2015 Impact in Yucatan doubled volcanic activity in Deccan Traps
https://www.theguardian.com/science/2015/oct/01/asteroid-that-killed-dinosaurs-also-intensifiedvolcanic-eruptions-study
Revised 21 March 2016