GEOL 102 Historical Geology
Spring Semester 2008
The Cenozoic Era VI: Living with the Ice Ages
In the near future:
- Without human influence, perhaps continued warming followed by another glacial advance
in 10 kyr or less
- With humans changing global CO2 levels, we may have kicked out of the
glacial-interglacial cycle: perhaps a return to something like Pliocene climates and sea
levels?
- Simulations of rising sea levels can be seen here,
and the East Coast of the U.S. in particular here.
(Melt ALL the continental ice, and get this)
- Massive extinctions ongoing, particularly among large vertebrates. Also, massive
habitat loss and redistribution (homogenization) of biota
Longer term changes:
See here for a possible future-geography
at –50 Ma (i.e., 50 million years from now),
here for the Earth at –150 Ma, and here
the next supercontinent (Pangaea Ultima) at –250 Ma
Longer term future historical geology is uncertain. Some suggestion that there may
only be enough radioactivity left for a few hundred million years of plate tectonics
(maybe less than 50 myr!). Regardless of exact timing, plate tectonics will eventually end.
When that stops:
- Erosion and isostatic rebound will wear down continental rock until only a few specks (if that)
are above sea level
- CO2 will get absorbed by weathering, lowering greenhouse gas level
- With not volcanic input, lots of atmospheric gasses will not be replenished. Net loss over
time into space. Note that as atmospheric composition changes and density decreases, stability
of liquid water at Earth's suface called into question: maybe all freeze? maybe all evaporate
and lost to space?
- With reduced carbon and other cycles, life will get progressively starved. When liquid
water becomes unstable at Earth's surface: extinction of wild metabionts
- Question if ultimate fate of Earth will be like Mars, like Venus, or unique
To Previous Lecture.
To Syllabus.
Last modified: 2 January 2008
