For Dr. Hoffman’s Snowball Earth website,
FAQs, and Teaching slides, visit his Harvard and NSF funded website by
Although this site might seem more geared to college students
and instructors, it is rich in background materials for science teachers,
and will be useful to many, including honors high school students, and
anyone interested in earth science, geology, climate change, global warming,
extreme climate events, ice ages, geological history, and the evolution
of life on Earth. Look for “Commonly Asked Questions” and
& Topics Covered
Overview of the Greenhouse Effect,
Carbon dioxide and humans, with illustrations and charts - 1:30
Windows Media -7MB / Quicktime
Students Had to Say...
One Teacher Used the Thin Ice DVDs
and Readings to Teach
Dr. Paul Hoffman
Dr. Paul Hoffman, a field geologist from Harvard University
and one of the world's authorities on "The Snowball Earth Theory"
came into Ms. Chang's Earth Science Class at Wellesley High School
to meet with students and talk about how the planet works, using Snowball
Earth as a case study.
Dr. Hoffman talking to students in Ms. Changs classroom
Dr. Hoffman explaining the clues left behind in rocks
after an ice age and how scientists learn to read these rock-prints
to reconstruct the past
Why Snowball Earth Theory? There isn't a story more
fascinating and puzzling than this one, and there isn't a more engaging
scientist-explorer to tell it than Dr. Paul Hoffman, whose field work
has brought him to the far corners of Earth (sometimes on all fours)
digging up the evidence himself.
In Africa, during field work. Dr. Hoffman in Namibia
chatting with a graduate student during a break from examining the
cliffs behind him. (Photo by F. Macdonald.)
According to what he discovered, the Earth became a
snowball, and more than once. Could it happen again? What is he unearthing
out in the field? Students and teachers alike are challenged to apply
all they know about how the earth system works to try to connect the
dots and figure out just what makes the planet tick and what made
it go haywire.
Kap Weber: Field Camp
in East Greenland
Snowball Earth Base Camp in East Greenland. Reading the rock record from
the late Neoproterozoic (600-800 million years ago).
layers in Namibia, Africa" (Maieberg Vista)
Unearthing Earths stories. Beautifully exposed layers of rock in these
Namibian cliffs. Each layer has a story to tell.
Banded iron formations. Credit:
Photo courtesy of P.Hoffman
Iron formations are precambrian (before complex animal life) sedimentary
rocks. They are highly magnetic and can cause detectable variations
in Earth's magnetic field, such as the Kursk Magnetic Anomaly that
was remotely sensed by satellites. Kursk is located in western Russia,
at the confluence of the Seym and Tuskar rivers.
Glacier Tip, Baffin-Island
The edge of the Baffin Glacier
“Many lines of evidence support a theory that
the entire Earth was ice-covered for long periods 600-700 million
years ago. Each glacial period lasted for millions of years and ended
violently under extreme greenhouse conditions. These climate shocks
triggered the evolution of multicellular animal life, and challenge
long-held assumptions regarding the limits of global change.”
Paul F. Hoffman and Daniel P. Schrag, Harvard University August 8,
Here's what Ms. Chang told Dr. Hoffman:
"I want to create a situation where curiosity is contagious,
and everyone can feel it and get drawn into it, where it's safe for
my students to open up and take off with you. If we can create that
dynamic exchange between scientist and 15 year olds - and then actually
capture it on film.... we will have created a truly original and exceptional
Here's what Dr. Hoffman told Ms. Chang:
"I just want to get them thinking. I want to prod them to
ask: why are things the way they are?"
Here's some advice Dr. Hoffman had for all science teachers
"Make them curious. Get them to ask basic questions: Why
is Earth warm when space is dead cold?"
"Kids are oversupervised... They are deprived of time
to be out of doors, alone with nature, and with their imagination
and their imaginary friends."
"Any scientist will tell you that an active imagination
is very important."
Here's what Dr. Hoffman said to the students:
“I’m a geologist. How do
I do something useful?"
“We don’t know how long it
will take the Greenland Ice Sheet to slide into the ocean.”
“Carbon dioxide goes up and down with ice ages. We know
this from the bubbles in the ice. We have samples of air almost
one million years old.”
Snowball Earth base camp in Namibia. Camping by the river.
Part of the fun of
being a geologist during field work in Africa
Some of the sights at the watering hole.
What Dr. Hoffman said afterwards about the students' interview:
"I was struck by their interest in how and why I am motivated
to be a scientist."
What students said about Dr. Hoffman:
"I like the way he said 'we truly don't know' instead of
just making up an answer." (Najauna)
"I liked learning directly from a scientist who's doing
work in the field, and not just from a text book." (Jack)
"This was the first time I ever met a scientist who's actually
doing work in what we're studying in class." (Jenny)