announcement

1
announcement

• Friday 27th 4th exam review Weds. 25th, 5.15
  PM, here
• Read from p. 322 (where you left off) through
  sec. 11.4 -- minimizing the hazard -- can we
  really bypass extinction due to an impact?

2
Today/Wednesday

• Meteor impacts what where how often
• Extinctions
• are they really closely related?
• did a meteor impact really kill the dinosaurs?
• if not, what did?!

Please turn on your clicker
3
Please click true or false if a meteor is big
enough to cause damage it will leave an impact
scar

1. T
2. F

4
Most meteors come from

1. Comets from outside the Solar System
2. The asteroid belt
3. Mars
4. A planet that once existed between Jupiter and
   Saturn

5
Which was is this comet traveling?

1. towards the sun
2. away from the sun
3. could be either towards or away

6
Why are meteorites usually very smooth?

1. They are usually reworked in rivers before they
   are found
2. Most are found in Antarctica, where the ice works
   them
3. They are melted by the atmosphere

7
Which part of the moon has more impact scars?

• Basalt flood plains
• Granitic highlands
• Both areas have
• about equal amounts
• of impact scars

8
What do impact scars on the moon tell you about
the timing of impacts in the solar system?

1. Most of the impacts have occurred in the last 3
   billion years
2. The timing of impacts has stayed more-or-less
   constant over time
3. Most of the impacts occurred more than 3 billion
   years ago

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Some terms

• The vast majority of impacts occurred gt3 b.y. ago
  -- were just seeing the remnants
• Meteor
• Meteorite
• meteorite
• asteroid
• Kinds of meteorites
• stony
• iron
• Magnitude/frequency

10
One more clicker Q (ok, 2)
11
On Friday if I ask you which disasters are the
best for discussing magnitude/ frequency, what
will you say?

1. Earthquakes volcanoes
2. Volcanoes severe weather systems
3. Severe storms meteors
4. Meteors earthquakes

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Why?

• Earthquakes and volcanoes are nearly always
  moderate in size and in severity
• Volcanic eruptions are usually big and not too
  common, and severe systems happen all the time
• Severe storms and meteors are common occurrences
  every day
• Meteors and earthquakes happen at small scales
  every day

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Other concept things

• Our protection system
• Speed of impact

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Remember these things

• You have a greater chance of being killed by a
  meteor than winning the jackpot in the lottery
• The Earth is a small target in the cosmic
  shooting gallery (P Abbott)

15
Meteor craters

• Simple vs complex the ground becomes jello, but
  on different scales
• Meteor Crater
• Yuty Crater (Mars) -- better exposed/ preserved
  than any large crater on earth

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simple
www.gc.maricopa.edu
http//www.metsoc2006.ethz.ch/bilder/Shatter-BedaH
ofmann.gif
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complex
http//nssdc.gsfc.nasa.gov/imgcat/hires/vo1_003a07
.gif