DEFINITION OF CENOZOIC TECTONICS AND CLIMATE

Cenozoic global tectonic patterns are dominated by the opening

of the Atlantic Ocean, closure of the Tethys Ocean and

formation of the Alpine–Himalayan Mountain System, and

mountain building in western North America. Uplift of

mountains and plateaus and the movement of continents

severely changed oceanic and atmospheric circulation patterns,

changing global climate patterns.

As the North and South Atlantic Oceans opened in the

Cretaceous, western North America was experiencing contractional

orogenesis. In the Paleocene (66–58 Ma) and

Eocene (58–37 Ma), shallow dipping subduction beneath

western North America caused uplift and basin formation in

the Rocky Mountains, with arc-type volcanism resuming

from later Eocene through late Oligocene (about 40–25 Ma).

In the Miocene (starting at 24 Ma), the Basin and Range

Province formed through crustal extension, and the formerly

convergent margin in California was converted to a strikeslip

or transform margin, causing the initial formation of the

San Andreas fault.

The Cenozoic saw the final breakup of Pangea and closure

of the tropical Tethys Ocean between Eurasia and

Africa, Asia, and India and a number of smaller fragments

that moved northward from the southern continents. Many

fragments of Tethyan ocean floor (ophiolites) were thrust

upon the continents during the closure of Tethys, including

the Semail ophiolite (Oman), Troodos (Cyprus), and many

Alpine bodies. Relative convergence between Europe and

Africa, and Asia and Arabia plus India continues to this day

and is responsible for the uplift of the Alpine-Himalayan

chain of mountains. The uplift of these mountains and the

Tibetan Plateau has had important influences on global climate,

including changes in the Indian Ocean monsoon and

the cutting off of moisture that previously flowed across

southern Asia. Vast deserts such as the Gobi were thus born.

The Tertiary began with generally warm climates, and

nearly half of the world’s oil deposits formed at this time.

By the mid-Tertiary (35 Ma) the Earth began cooling again,

culminating in the ice house climate of the Pleistocene, with

many glacial advances and retreats. The Atlantic Ocean

continued to open during the Tertiary, which helped lower

global temperatures. The Pleistocene experiences many fluctuations

between warm and cold climates, called glacial and

interglacial stages (we are now in an interglacial stage).

These fluctuations are rapid—for instance, in the past 1.5

million years, the Earth has experienced 10 major and 40

minor periods of glaciation and interglaciation. The most

recent glacial period peaked 18,000 years ago when huge

ice sheets covered most of Canada and the northern United

States, and much of Europe.

The human species developed during the Holocene

Epoch (since 10,000 years ago). The Holocene is just part of

an extended interglacial period in the planet’s current ice

house event, raising important questions about how the

human race will survive if climate suddenly changes back to a

glacial period. Will humans survive? Since 18,000 years ago,

the climate has warmed by several degrees, sea level has risen

500 feet (150 m), and atmospheric CO2 has climbed. Some of

the global warming is human induced. One scenario of climate

evolution is that global temperatures will rise, causing

some of the planet’s ice caps to melt, raising global sea level.

This higher sea level may increase the Earth’s reflectance of

solar energy, suddenly plunging the planet into an ice house

event and a new glacial advance.

See also CLIMATE CHANGE; PLATE TECTONICS.

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