Kolbert, “Enter Anthropocene–Age of Man”

(Geological discussion)


1.      Anthropocene: Name of potentially new geological epoch defined by massive human impact on planet (over the last century or two?) See Geological Time Scale

         a.      Left the Holocene, which began at end of last ice age 11,500 years ago

         b.      Our impact will remain in geologic record

         c.      Note that geologists/stratigraphers have not yet decided on such a new epoch, but “many believe it justified”

2.      Impacts that might justify new epoch

         a.      Mass extinction: This has marked shifts in geological past

                   i.       Extinction rate 100 to 1000 times higher than occurred over last ½ billion years

         b.      Sea level rise, change in climate

         c.      Change in chemistry of oceans

                   i.       CO2 seeps into oceans acidifying them to point corals no longer construct reefs–might create “reef gaps”

         d.      “Human biomass already 100 times larger than that of any other large animal species ever walked earth”

                   i.       But not than the dinosaurs? Or than insect mass?

         e.      Fertilizer factories fix more nitrogen from air (into bio usable form) than all land organisms


3.      How decide new geological boundaries?

         a.      “The boundaries between epochs are defined by changes preserved in sedimentary rocks—the emergence of one type of commonly fossilized organism, say, or the disappearance of another.”



5.      Building cities most obvious way we have altered planet, but this stuff will erode and not be laid down in the sediment

         a.      From geo perspective, most visible effects are most transient


6.      Might see effects of 21st-century industrial agriculture (38% of ice free land used for ag) in pollen record–corn, wheat and soy pollen

7.      Change in composition of atmosphere–burning billions of tons of coal/oil–likely to be clearly discernable

8.      Reef gaps marked each of past 5 mass extinctions


9.      Our impacts may look as sudden and profound as that of an asteroid that brought the Cretaceous to an end 65 million years ago

         a.      Due to acidification of oceans and reef gaps?

10.    When to end Holocene and start Anthropocene?

         a.      Some say with invention of ag about 8000 years ago, led to deforestation, led to increase Co2 and stopped the start of new ice age; humans been dominant force on planet since then

         b.      Others say 1850, when co2 began an uninterrupted rise

         c.      Others say mid 20th century when population and consumption growth exploded

         d.      Others have suggested when we exploded nuclear bombs the result of which left a radiation signature that will be evident in the future.

Study question on Kolbert, Enter the Anthropocene

1.      Describe and discuss the geological debate about whether or not we have entered a new geological epoch. What sorts of things determine a new geological time period? What effects have humans had that might justify such a designation?