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Chemical Weathering

Chemical weathering is the breakdown of rocks and minerals by changing their chemical composition by water, carbon dioxide, oxygen and other compounds.

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Oceans 4.4 Ga

Oceans 4.4 Ga


Credit: Gail
Source: http://www.flickr.com/photos/48698665@N00/3501358558
License: CC BY-NC 3.0

One small crystal from Western Australia indicates the presence of an ocean very early in Earth history. And where there’s water there may be life.

Why It Matters

Credit: Teravolt (talk)
Source: http://en.wikipedia.org/wiki/File:Zircon1.JPG
License: CC BY-NC 3.0

Zircon [Figure2]

  • One zircon grain is the oldest material we have that found on Earth.
  • The grain is formed 4.4 billion years ago (Ga or giga annum), only 150-million to 300-million years after the planet.
  • During the Hadean, meteorite bombardment kept much of Earth’s surface molten.
  • The zircon formed at about 680° C, which indicates the presence of water.
  • The zircon may have formed in rocks that melted at a subduction zone.

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With the links below, learn more about the oldest zircon. Then answer the following questions.

  1. Why is the oldest material a zircon grain?
  2. Why don’t we have rocks that old?
  3. How does the titanium thermometer work?
  4. Why does the 680o C formation temperature for the zircon indicate the presence of water?
  5. Why is the early presence of an ocean so exciting to scientists?

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Image Attributions

  1. [1]^ Credit: Gail; Source: http://www.flickr.com/photos/48698665@N00/3501358558; License: CC BY-NC 3.0
  2. [2]^ Credit: Teravolt (talk); Source: http://en.wikipedia.org/wiki/File:Zircon1.JPG; License: CC BY-NC 3.0

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