qTectonic Scale: the longest time scale of climate change on Earth, which encompasses
most of Earth’s 4.55-billion years of history.
qTectonic processes driven by Earth’s internal heat alter Earth’s geography and
affect climate over intervals of millions of years.
qOn this time scale, Earth’s climate has oscillated between times when ice sheets were
presented somewhere on Earth
(such as today) and times when no ice sheets were presented.