Geology is the study of the Earth including its formation and its relationships within the solar system. So far in this course we have looked at some hazards originating right here at home but actually the biggest potential hazard, although very rare, comes from elsewhere in our solar system. There are a huge number of objects greater than 10m in diameter that cross the orbit of the Earth. These are termed "Near Earth Objects" or NEOs. These mostly burn up or break up in the atmosphere before reaching the surface (Table 5-1) but about one object in the 10m size range hits the Earth each year. The ones we really have to worry about are those greater than about 50m in diameter. As we will see, life on the Earth has been affected by collisions with space objects in the past, and collisions will most likely affect the Earth in the future. Note that many of the numbers listed in this chapter are not absolute because more and more extraterrestrial objects are being found every year and their orbits are being computed more accurately.
Upon completion of this unit you should be able to:
1. Explain the classification
of extraterrestrial objects.
2. Understand the different types of meteorites and how they are related to the Earth's internal structure.
3. Say where asteroids come from and how they might have been moved into Earth-crossing orbits.
4. Define the different types of comets and say where they come from.
5. Discuss the factors that relate to energy release during an impact event.
6. Discuss the many things that happen during an impact event.
7. Understand the various ways in which impact events are recorded in the rocks
8. Discuss the many things that happen on Earth after a major impact event.
9. Understand clearly the theory of dinosaur extinction as it relates to a giant impact event.
10. Discuss the ways in which humans are trying to predict the path of extraterrestrial object and how successful the efforts have been.
11. Discuss the merits of various techniques suggested for deflecting large extraterrestrial objects away from the Earth
Required ReadingsAbbott, P.L., 2014. Natural Disasters, Ninth Edition:
Abbott, P.L., 2012. Natural Disasters, Eighth Edition:
|Amino Acid||Kuiper Belt|
|Asteroid Belt||Mars Meteorite|
|Barringer Crater||Nuclear Winter|
|Comet Tempel 1||Richter Magnitude|
|Cosmic Winter||Shatter Cone|
|Impact Breccia||Torino Scale|
|Impact Crater||Widmanstätten Pattern|