| 1. | This system includes the near-surface rocks, the soil, and the atmosphere.
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| 2. | Surface rocks help hold in moisture, keeping the reddish soil fertile.
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| 3. | In geologic time much of the surface rock has been eroded by glaciation.
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| 4. | So does helium in porous surface rocks, which tends to dissipate fairly quickly.
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| 5. | This included removing of surface rocks and filling any crevasses.
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| 6. | Desert varnish collects on the exposed surface rocks over time.
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| 7. | Chlorine-36 nuclides are also measured to date surface rocks.
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| 8. | A total of 22 percent of the surface rock in this area is Pennsylvanian epoch.
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| 9. | Common surface rocks include basalt, andesite, pumice, and obsidian.
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| 10. | The surface rock above laccoliths often erodes away completely, leaving the core mound of igneous rock.
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