Intro: Snowball Earth is a fascinating science
story that brings together and applies all the sciences. It allows teaching
by “story telling” - in this case, using one of Earth’s
most mind-boggling extreme events in its past – one with connections
to our modern story of climate change. It also lends itself to the portrayal
of scientists, how science works, the ways of science, and discovering
how inventive and creative scientists are to come to know what we think
we know.
Preparation: After students studied the climate
system and the triggers that cause climate change, they studied Snowball
Earth as a case study of abrupt climate change in Earth’s past,
one with caused extreme changes to every facet of the earth system -
biological, chemical, physical changes to the earth system and the evolution
of life. They were simultaneously introduced to the two scientists at
Harvard who are the leading proponents of the Snowball Earth hypothesis.
Students watched the DVDs of Dr. Hoffman and Dr. Schrag as part of the
unit so they were introduced to the scientists, and to the science they
would need to help them apply their knowledge. They were also asked
to brainstorm their way through the puzzles, culminating in an exercise
where they had to form groups to come up with working hypotheses to
explain how the Earth system could get out of a Snowball Earth event
(an earth science question). Other open-ended questions could be biological:
what would happen (hypothesis) to the chemistry and biology of oceans
and existing ecosystems 800 million years ago if the oceans were completed
covered in ice? Physics question: how would a planet( Earth) be affected
physically by a change from a liquid surface to one completely covered
in ice? Then they were given the Scientific American article to read.