Page 65 - Earth's Climate Past and Future

PART II

Tectonic-Scale

Climate Change

n this part we examine the longest time scale of primary focus of Part II. Evidence of climate change over
climate change on Earth, the tectonic scale. this long span of Earth’s history comes mainly from
ITectonic processes driven by Earth’s internal heat sediments preserved on the continents and their margins.

have altered Earth’s geography and altered climate for We explore the following basic questions about
billions of years. Prior to the last several hundred Earth’s tectonic-scale climate history:
million years, the record of climate change is relatively
sparse, and the basic configurations of continents and
• Why has Earth remained habitable throughout its
oceans are poorly known. Yet we do know that Earth’s
history?
climate remained relatively moderate, neither cold
• What explains the changes in Earth’s climate over the
enough to freeze solid nor hot enough for its oceans to
last several hundred million years?
boil away. Earth has a built-in thermostat that allowed
• Why was Earth ice-free even in polar regions 100 Myr
it to avoid those extremes.
ago?
As the movements and locations of the continents
• What are the causes and climatic effects of changes in
become better known, greater insights into climatic
sea level through time?
cause-and-effect relationships emerge. We know that
• How did the apocalyptic asteroid impact 65 Myr ago
Earth’s climate has oscillated between times when ice
affect climate?
sheets were present somewhere on Earth (such as today)
• What caused Earth’s climate to cool over the last
and times when no ice sheets were present (about 100
55 Myr?
Myr ago). These oscillations and their causes are the